Repairing Your Radiator and Replacing Your Imperial's Radiator Cap

Imperial Home Page -> Repair -> Cooling System -> Radiator and Cap

Tip from Paul:

Note on overheating........... It has been my experience on older radiators that flushing does not restore cooling capacity. If the radiator is still pretty solid, no seeping leaks where the core joins the tanks, you can have your radiator shop "rod out" the radiator. This procedure involves removing one of the tanks, (unsoldering), and running a thin flat rod down through each tube to scrape or push out the scale that has accumulated. This procedure will really restore cooling capacity. If the radiator is already weaken by corrosion, vibration etc., a good radiator shop will advise you not to "rod out" the radiator because it cannot survive the procedure. In this case, have the radiator shop "recore" the radiator... this is replace the tube and fin middle section of the radiator and use the original top and bottom tanks. For the '75-'78 Imperial, New Yorker, and Newports, have them try to get the "police" or "trailer-tow" core which will have an extra row of tubes and will also have a greater density of cooling fins. If you do this, your cooling problems will be over.

Tip from Bill:

Chronic overheating even after doing all the external stuff (radiator, hoses, water pump, thermostat, timing check, fuel mixture not too lean, etc etc,) usually means the block is filled with crud in the water jackets. The cure (half-way) is to pull those core plugs you can get to and flush with a garden hose/sprayer. The cure (real) is to pull the motor, pull ALL core plugs and flush the block. But before doing that, put an aftermarket gauge and sending unit in, even just let it ride on the floor if you don't want to mount it, and see what its really doing

Tip from Bob about 3-row radiators:

I've been told by more than one mechanic that adding rows to the radiator does not eliminate overheating. (1) the thermostat will keep the temperature to 180 (or whatever it is) and additional rows only mean that there's more water flowing, not that it is cooler and (2) the water pump is designed to cause a flow of x gallons per minute so water movement remains the same. (3) The most important things to consider is an unobstructed radiator, clean block (& heads) good (non-collapsing) hoses and the proper water pump. Also, if the fan is a coupling type, make sure it is operating correctly.

Tip from Gordon:

PLEASE, LET YOUR READER'S KNOW THE TRUTH ABOUT ALUM-A-SEAL. I put a container of it in my radiator last week and not two blocks from the NAPA store my car overheated.  I pulled the car over to allow it to cool down.  All was well for the four mile trip home.  In the three years I have owned this car it never has overheated.  I then took my child to soccer practice and ALL HELL BROKE LOOSE.  The engine temp went wild.  I wasn't able to get off of the expressway (1/2 mile) for only a few minutes, but, the damage was done.  I was towed in and the news was not good.  In a few short miles from the start of my trip to the end MY ENGINE WAS SHOT.

The garage scolded me like a child for putting that junk in the system.  They replace radiators on 6 to 8 vehicles every month that have problems as a result of Alum-A- Seal.  I guarantee you Alum- A - Seal doesn't put the disclaimer on it packaging.

Please, find another solution. I now have two choices before me, replace the engine ('98 Taurus) or dig deep and buy a new car.

Tip from Loren:

Some people think when they see coolant under their car they need a new radiator.  But another culprit could be that the sodder joint on the top of the radiator let go." When I had a new core installed in the radiator on my '64, Ron at Greenwood Radiator in Seattle suggested the factory suggested cap pressure of 14 lbs. or 16 lbs. with A/C is so high it does split tank seams on these radiators. He furnished me with a 7 pound cap. I use a coolant recovery system and have not had any problems with coolant loss or overheating. I am also looking forward to not splitting the seam at the top of the tank. It's been about a year since I did the radiator and heater cores, so that's at least a start of a time test.

Question from Jason:

My radiator is begun to leak again. It has been to the shop twice in the last two months for the same problem. It continues to leak under the lip of the top tank on the engine side in the center.

I would like to keep this setup because I have an original CCPD stamp on the top of the radiator tank there a more modern unit that will bolt in that I could use for now?


From Dave:

Just have it recored! Thay'll use the same top and bottom tanks, and replace the finned part in the middle.

From Roger:

After 45 years, sometimes metal just refuses to be repaired. Your repair shop might be trying valiantly, but as Dave said, It's time to get it re-cored.

From Dave T:

Bars Leak is not a good idea as it is the consistancy of honey and settles in the lowest part of the cooling system, your heater core. There is a product called Alumi-seal that is actually small pieces of aluminum (like a dust) that fill the hole as the leak continues. You may need two of them. After a short time of running and leaking, the hole becomes plugged and many times, fixed permantly. If that doesn't work, nothing will work and it will need to be replaced. Alumi-seal can be found almost everywhere car parts are sold. It won't hurt anything in the system and is even credited with lubricating the water pump. It has worked for me on a cracked block (a thee inch crack just under the head) that must have frozen before I got it, and is still working today.

Follow-up from Dave:

I've always had the opposite thoughts. Bar's Leaks is used by most manufacturers even in new cars, and is guaranteed not to void your warranty or damage the car. The metallized versions of the leak stopping products do not make those gaurantees. Bar's Leaks is basically just little organic fibers. The pellets may sink to the bottom at first, yes, but as soon as they dissolve, all of the microfibers will stay suspended in your coolant.

I have used alumi-seal twice on leaks, and twice my water pump has fried within days afterwards. Other folks, like Dave Todd, have had great success with it though. Based on my experiences and some horror stories I have heard from others, I personally would never come near it again.

From Dave G.:

Personally, I would get it recored. Things that stop leaks may work great, but I question the permanence of them. I'd say the leak stoppers were more to help you limp home, or possibly to the radiator shop. I suppose its because I don't like to drive with something "works", but isn't "fixed". I don't think anyone wants to spring a leak on the highway at night (it wasn't fun), and I just can't see any reason to leave it to chance...

Question from Roy:

A friend of mine bought a ' 68 NYer a short time ago and I had occasion to look at it this morning. Aside from the usual minor problems, it had a pinhole in a radiator tube just below the tank. We took a quick trip to the auto parts store to get some Alumaseal, however, when I pulled the radiator cap to put it in, I saw the telltale tan color indicating oil in the coolant. When my friend asked what the bad news was I told him it was time for new head gaskets or to ignore the problem and pray it doesn't get worse. Trying to keep a positive outlook, he quizzed me on other possible causes, which left me at a loss. Finally, he pointed to the transmission lines at the bottom of the radiator and asked what they were for, after I explained that they contained transmission fluid, he asked if that could be the cause??? Anybody have any comments on the causes of oil in the cooling system, could it be from the transmission cooler leaking inside the radiator?


From Dick:

Usually, if a 727 is leaking transmission fluid out of the cooling tank in the bottom of the radiator, there will be so much excess pressure in the radiator that the problem becomes immediately obvious (and please don't ask me how my wife found THAT out!). There is a simple and easy way to determine if your head gasket is blown to the compression chamber, that is to beg, borrow or steal a Balkamp block seal tester kit (it bubbles the air from the radiator through an indicator fluid. The resulting color change, if any, tells you how much compression gasses are getting into the coolant). The kit costs less than $50, and I think it's a good thing for a car collector to own, if he is maintaining more than one or two cars. Oil in the water could also mean someone has put soluble oil in the coolant, perhaps thinking the water pump needs it (an old remedy, seldom needed now). Before spending a pile of money pulling the heads etc. try flushing and cleaning out the cooling system and refilling with plain water for a few days, to see what turns up. Don't forget to drain the block (two drains, one on either side, between # 5&7 and between # 6&8.) If you don't see a recurrence of glop, you can put the anti-freeze back in there and hope.

From Steve:

I would first check the transmission fluid and engine oil to see if there is any contamination of it too. A pin-hole leak in the transmission cooler that is inside of the radiator tank will put transmission fluid inside of the radiator. When the engine is off, pressure will still remain in the cooling system for a little while if the engine was up to operating temperature, the radiator cap is ok, etc...thus putting a small amount of coolant into the transmission lines which will mean slow death for the transmission once the car is used again. The same process will apply if there is a crack in the block between a water jacket and an oil galley. Check the oil to see if it appears contaminated. For a head gasket to blow between a water jacket and an oil galley is not very common. They are more apt to blow between cylinders or cylinder to water jacket....not from water jacket to oil passage. And as far as I can remember...oil does not even pass thru the head gasket area. I believe the top end of the engine is fed via the lifters and pushrods.....and then the non-pressurized oil flows down thru large passages in the top of the head, through the holes near the camshaft and then into the oil pan. Roy, why don't you recommend to your friend to get a auxiliary transmission cooler that attaches to the front of the radiator? Wouldn't it be nice if the transmission cooler in the radiator was leaking and all you had to do was install an aux one thus eliminating the one in the radiator??? I have one installed on my '75 Imp along with a sending unit and gauge to tell me what temp my transmission is running at. It usually runs at about 130 to 150. Heat is the #1 killer of automatic transmissions. Using the one that is in the radiator only cools the fluid to whatever the coolant temp is.

Question from Frank:

I have developed a small leak in my radiator, it is at the seam where the top tank is. Someone suggested using the some gunk sealer to fix it. Can it do any harm adding it to my Imps cooling system? If I pull the radiator and bring it to a shop to be fixed I plan on repainting it before I put it back in the car. I would like to remove a ding that is on the top of the tank near the corner. Do they do do that sort of thing at radiator shops and how much more would it add to the cost of repairing the seam?


From Paul:

I would stay away from any type of "easy-fix" or gunk to repair a radiator. The money you save on the repair could end up costing you a lot more if you have a complete cooling system failure. I would suggest having the radiator repaired by a shop, and make sure they "rod it out" instead of just resealing the tank. As far as the dent in the tank, they may be able to bang it out a bit for you, that would really depend on the shop, usually they don't worry about the cosmetics too much.

From Elijah:

A few years ago, I learned to avoid this stuff at all costs. It has the potential to clog up water passages and heater cores. And if your car has AutoTemp, it can wreak havoc with the water valve.

Go ahead and take the radiator to a shop. Having the leak fixed and the radiator rodded out should be well under $100. And every shop I've ever taken a radiator to has painted it as part of the service

From Dick:

In general, it is a good idea to be very sparing with paint on a radiator, as it impedes the heat transfer. If you want to paint the tanks, fine, but keep to a very thin 'dusting' of flat black on the fins.

Putting sealant in a car is always a last resort, as it inevitably hastens the day when the whole cooling system will need to be cleaned out, including the block passages. If I were stuck with a hole in my radiator in the middle of the Sahara Desert and only one 6-pack of beer to keep the cooling system full, I'd use sealer too (I'd use the powdered aluminum stuff that is usually next to the cash register at your local NAPA store, which sells for 99 cents), but unless it is an emergency like that, I think you should have it fixed right. If they take the top tank off to fix it, perhaps you can persuade them to push the dent out for you, but copper is notoriously brittle when it gets old, they may refuse to take the chance. Depending on how bad the leak is, and where it is, they may be able to solder it for you without even removing it from the car (or if you have a propane torch and the right solder and flux, you can do it yourself).

Question from Zan:

I need a new radiator and a new one is going to cost me $400.  Is there a cheaper solution?

Reply from Dick:

A recore may be your best option. Any used replacement you find is likely to have the same problems you are facing, unless you know the history of the car it came from, and it was recently recored or at least rodded out. $400 is a pretty typical price for a recore in California. It may be possible to buy a complete new radiator for less money from a wholesale radiator supply house. I recently bought a brand new one for my 69 Newport from Newman and Altman in South Bend for $392. Do you have a mechanic friend who could order it for you? Do you know the part number (it's on the top tank)? I have one from about that era which I know needs to be rodded out, but it is a solid core. You are welcome to it if you pay the packing and shipping cost.

Question from Dave (413):

What should the correct poundage be for a radiator cap on a 413 engine?

Reply from Elijah:

16 pounds is what you need.

Question from Anthony (1956):

Does anyone know where I can get fan belts for my '56 Imperial? I want to replace them all. they are the double fan belts that have to be cut from the same run.

Reply from Rodger:

I always go to NAPA for my belts. They have a top grade line of belts that carry a replacement clause if the belt should break before its expected life span. If you can find a friend who can get the shop price for you ... do so. I just purchased a set of belts for the 66 and the A/C belts alone cost me $ 21.00 ( the power steering belt was $10 - 11 and I forget what the water pump belt was ).

Question from Phillipe (1957):

When my car runs at slow speed or if I wait at a red light the gauge climbs to 3/4 high. At normal speed the gauge is at N or slightly higher depending exterior temperature. At high speed (70-80 mph) the temperature climbs again. Note that the radiator is new, the thermostat is not removed.  I've tried to make some temp. tests: after driving, I parked the car, temp was 3/4 high so very hot. I turned off the engine and remove (slowly and with care) the radiator cap. As you (and I ) expected, a lot of steam, some coolant spilled from radiator and the coolant in radiator boiled. I put a jam thermometer in the radiator and I read 200 F (gauge was at "H" mark).  I immediately ran the engine (w/o the cap and thermometer always in radiator) and the temperature decreased to 180 F.. (which correspond to the 2nd "leg" of N on gauge).  I let the engine drive some minutes and surprisingly the temp didn't increase.  So why, with cap, the temp is higher than without?  Do I have a problem with the cap  which doesn't allow a too high pressure to decrease (I never saw the coolant spilling from overheat tube) ?  What do you think of an expansion tank?


From Phil:

I hate to say this, Phillippe, but I think you have a head gasket going bad. My 63 300 did the exact same thing in the exact same way. I changed the thermostat, removed it, and recored the radiator. Nothing helped much until I bit the bullet and pulled the heads. It's also a good time to flush out the block, cause you can access the rear somewhat through the holes in the block. I think why the temperature gets higher with the cap on, is that it puts enough pressure on the head gasket for leakage to start.

From Dick: 

I have added expansion tanks to some of my cars which did not originally come with them, because I live in an exceptionally hot area, and often had the experience of a car "burping" out some coolant through the overflow tube after a hard run. This does not necessarily mean the engine is excessively hot, as it will also occur when the coolant had been overfilled when cold (higher than 2 inches below the cap, usually).

Expansion tanks have been provided on some cars starting in the 30's; it was a good idea then and now. I added one to a 1956 car (has to be nameless, here) which had this "burping" problem prior to a 7000 cross country trip during the hot summer months, with AC going full blast most of the trip, and the car did not use one drop of coolant for the whole trip. Pretty impressive. I found that if I checked the expansion tank after a hard run, there was about 1 quart in it, which disappeared when the engine cooled down.

Be aware that to add an expansion tank, you have to get an expansion tank type radiator cap. They are different, since they must seal to the top flange in addition to the inner flange. They are labeled as to application in the Stant Catalog. If your present pressure cap is holding pressure, and is the correct one, I think you can assume it is OK, as the design is pretty "fail-safe", meaning when they fail, the failure is such that it releases pressure at too low a threshold, not too high. Removing a pressure type radiator cap when the engine is hot will almost always result in some coolant loss, as the hoses will collapse slightly, adding to the expansion of the hot fluid and propel coolant out the top of the system.

200 degrees won't hurt your engine at all, in fact modern engines are designed to run above 200 as a normal practice. You seem to indicate that "H" on your gauge is around 200, and with 50% coolant/water mixture and a 14 pound cap, you are not going to be boiling fluid unless the temperature goes above 240 or so (actually I think it's 258), so if you never see over "H" on the gauge, and that only after shutting down after a run, I am not convinced you have a problem. Since even idling in hot weather only produces a 3/4 indication on the gauge, I don't think you have a serious problem.

One thing you said worries me, though, and that is the fact that the gauge creeps up at high speed. This could be a consequence of the aerodynamics of your front end shrouding letting air bypass the radiator, but it could also be a collapsing lower hose at high speeds. Even with a pressurized system, the water pump spinning at 3500 RPM can pull an actual vacuum on the lower hose, which can cause it to pinch off the water flow to trickle until you slow down. Lower hoses should always have an inserted spring to prevent this, but many are not supplied with replacement hoses, you have to transfer it from your old hose. Also, many mechanics seem to misunderstand the purpose of this spring, and discard it. If you can feel the spring in the lower hose, relax about this, but if you can't, I'd replace it before any more high speed driving.

 From Bob:

One check to make is what your water temperature actually is. One of my cars continually seemed to run "hot" after major engine work and I finally took it to the radiator shop that re-cored the radiator. They used an external temperature gauge/sensor (infra-red?) and checked all the hoses, radiator, etc. and got lower/normal readings. They also then used an accurate dial temp gauge to check the water temp - all normal. Their conclusion was "no problem".

I got a new, inexpensive water temp sensor and now my temp gauge reads more "normal" and I worry less. Conclusion: If you have a good radiator shop in your area, get an opinion from the "pros".

Question from Jay (1964):

I noticed last summer that my '64 was starting to run hotter than usual. I had the same ticking or squeaking sound coming from the water pump. I replaced it and the fan clutch on the suggestion of my mechanic. Since then it has been running as cool as ever (even in our 115 degree desert heat in Palm Springs).

Reply from George:

A "few" tips from the HOT south. 

a. Park in the shade (this is for you, not necessarily the car)....   

b. open the hood, being CAREFUL not to disturb the hood ornament (although I could use another addition) 

c. Check that water pump (these tips are BEST performed with the engine OFF) 

1. Belts tight? (1"play).....  

2. George's famous shaft bearing test (that's the WATER pump shaft)...Grab fan blade, and try to "rock" it forward and back, if it rocks (and this is the shaft, not the blade)...bearings are at least going bad. If the shaft moves a lot it (the water pump) is REAL bad. 

d. Thermostat check ON THE CAR 

1. remove radiator cap (best done with engine cool) 

2. start car, let it run until it is "hot" and coolant is circulating 

3. if at any time the coolant appears to be "surging" or blowing violently from radiator you can be suspect of a bad thermostat .....likewise if the coolant movement inside the radiator stops/slows then speeds up (sort of ON/OFF movement) or doesn't move at all... the thermostat is stuck in closed position. 

4. if you can't tell this way, using a hot plate and a pot of water with a candy thermometer heat water to at least 180 degrees and suspend thermostat using dowel and heavy string into water ...continue heating and watch to see setting on thermometer when thermostat "opens'...this should be +/- 10 degrees of thermostats rating  

 e. Radiator cap: check the pressure    

Question from Tim (1962): 

Can anyone tell me what the correct thermostat temperature setting is for a '62 413cui.  The one in the car is 180 but the car is running really hot. Car also has a 15lb radiator cap. 

Reply from John:

It sounds like you need a real good engine flush and or radiator rebuild--- after that many years those radiators and heater cores can get really plugged up....

Question from Alison (1963):

I was putzing around this afternoon and began wondering about overflow tanks. I have known people that put them on cars that were pre such equipment and I wonder how valuable this is. My car will push out some antifreeze after a long drive and it might be nice to keep it off the floor. If I do put one how are they sized? I know smaller cars have smaller tanks, will a small tank just overflow?

Reply from Dick:

Before you go to this much trouble, try just not filling the radiator so full. Check your owner's manual, but I think you will find best results by filling to 2" below the bottom of the filler neck. Also, of course, make sure you are running the correct radiator cap. If you don't know what the correct cap is, e-mail me directly, I can look it up for you. Of course, the cap must be in good shape. Check this by feeling the top hose when you shut the engine off after it is thoroughly warmed up. The hose should feel stiff from the pressure, 14 PSI or so, and that pressure should persist until the engine cools off.

Question from Chris (1965):

I have completely gone over the cooling system on my ' 65. New H2O pump, thermostat, hoses, radiator recored, cap, everything and I am having a bit of a problem. The service manual says that the system will hold 17 quarts. I can only get 12 quarts in. I have run the car with the heat on full hot and the thing burps and gurgles and acts like an infant after a feeding but I can't get any more coolant in. What am I doing wrong? HELP. I want to get the thing done so I can take it in for an exhaust Monday. The thermostat opens and the upper hose gets hot so I know (or think that I know) that the entire system is available to take coolant.

Reply from Norm:

Several possible explanations: 

1) Whoever recored the radiator did so with a core that will not hold as much as the original. 

2) The FSM is not infallible. Example, it says that the gas tank holds 25 gallons when we all know that that figure should be 23. 

3) When reinstalling the heater core you did not check to make sure that the Ranco valve is interfacing with the slide cable in a manner that allows for full opening of the valve and full circulation of coolant through the core.

Question from Norm (1965):

My temp gauge almost never gets to the normal (middle) of the scale. I replaced the thermostat thinking it was stuck open and running like the Dodge, but that did not fix it.  The engine seems to be running too cold.  Any ideas?


From Dick:

Step # 1 is to find out what temperature your car is really running at. The electrical gauge on your dash is notoriously inaccurate. Go to your local supermarket house wares department and buy a "candy thermometer". These are dead accurate mercury vial thermometers that cover any temp you will ever encounter in an engine. Remove your radiator cap while the engine is cool, stick in the glass thermometer and start the engine. Let it idle until it comes up to the place on the dash indicator that it usually reaches - read the true temp, this will tell you if you have a problem. By the way, if you see fluid circulating in the top tank before the engine warms up, which I suspect you will, you have a bad thermostat, or one which is install wrong.

If you don't see fluid circulating from cold, note the temp on the glass thermometer when it begins to move, that tells you when the thermostat is starting to open. This should be within 5 degrees or so of the rated temp. If not, you have a bad thermostat, or it is not installed right. If your car is running a 160 thermostat, you might need to go to a 180, but I suspect your poor idle problem is caused by some other problem. Even without a thermostat, the car should warm up enough so that it runs OK.

From Carmine:

The temperature gauge is relative. Cold is not really "COLD". Remember, you are exploding gasoline inside your engine, I don't care what your gauge says, burning gasoline is HOT. Grab the exhaust manifolds if you want proof. (JUST KIDDING)!! The temp gauge on any Mopar that I've ever owned doesn't go past 1/4 scale if everything is OK and the weather is "normal" (50-90 F) Even at 100+ it shouldn't go past 1/2. You've got some other type of problem...Have you checked to see if the choke is coming off? Running too rich? Timing retarded?

From Jim:

Have you tried a 195 degree thermostat? Is the induction system working ok (not running too rich)?

Question from David (1965):

I experienced something yesterday with my ' 65 Imperial that I have never had happen before. After a drive of about 80 miles I went to put the car up and decided to check all the fluids to see if everything was okay since the car is not accustom to long trips especially involving speeds of 75-80 mph. Upon raising the hood I noticed some white foam around the radiator cap. During the trip the car never ran hot. The radiator was flushed, cleaned, and new hoses were installed about 6 months ago. There have been no signs of leaking in the past and the radiator has an appearance of a new one, no visual signs of corrosion (car has only 25,000 original miles). When I replaced the hoses 6 months ago, I also replaced the radiator cap. I have never had a car to foam around the radiator cap before. Does anyone know what causes this?


From Brad:

How much water pump lube did you add when you flushed-and-filled? Too much of the lube will cause foaming.

From Doug:

I have seen it before and it was oil getting in from a head gasket.  Does the foam fill oily and how bad is it.  Hopefully its just from the flush.  When its cold look in the radiator to see if the fluids look abnormal.  And keep a eye on the color of the oil.

From Dick:

Another source of oil contamination in the oil can be the transmission cooler. Sometimes this will seep into the coolant. Check your transmission fluid for appearance and level. If this leak gets bad enough, it will increase the pressure in the radiator enough to cause a leak or even a burst of a seam, so you need to find this before there is more damage. Oil in the water won't hurt the engine, but water in the oil, either in the transmission or engine, will cause a lot of damage, and pretty quickly. If you suspect this may be the culprit, disconnect the cooler lines at the bottom of the radiator. and pressurize the cooler n to 15 PSI or so, then check inside the top tank for bubbles coming up through the radiator core. Any at all is reason to replace or repair the radiator, quick like a bunny! It is OK to drive the car for a while with the cooler lines bypassed with a fuel grade (SAE 30R9) hose, held tight to the ends of the lines with screw type hose clamps, but don't tow any house trailers that way.

Question from Marc (1966):

I have a ' 66 Crown Coupe with a deceased radiator, P/N 2582972, which is unique to 66 only. I'm getting quotes to fix the radiator for $300 to $350 range, and new radiator quotes for $425 and up. Anyone got a good used one (that doesn't require rebuilding) or heaven forbid, a nice new one for a good price? Overheated minds would like to know...


From Bill:

My '60 Imp overheated and it was determined the original radiator was all plugged up, no rodding possible, etc. I was able to recore it, using thicker 2" core for more cooling capacity. The professional radiator shop charged $313 total, and it would have been a little less with the smaller thickness core. I just picked the car up this afternoon, two days later. I had already replaced the thermostat and sending unit, and confirmed my dash gauge was accurate. $300-$350 seems reasonable to me.

From John:

I'd vote for rebuilding the old one. This price sounds a little high, but even at that price it is good piece of mind. If you plan on keeping the car a while this is money well spent. Buying used is a gamble since often the seller doesn't know its condition & you end up at least having it cleaned or repaired .

Question from Jim (1967):

On a recent trip from Minnesota to Savannah, the 1967 exhibited an  interesting problem. Towards the end of the second day, the temperature increased above normal. This was after about 10 hours of driving. It eventually got hotter, until I decided to stop before bad  things happened. The next morning, I filled the radiator and continued on. About thirty miles from home, it began to get warm  again. I just took it out for a short drive and after parking, the post-flight revealed what had happened before: the coolant was coming out of the overflow tube.  It has an AVS carburetor, not an AFB.


From Kerry:

Radiator cap? Is it new and the proper pressure? Is the seat clean and smooth. Coolant should not run out the overflow unless pressure exceeds the design which should be when the engine is VERY hot. Short of damaging the engine but still VERY hot.

From Dick:

The AVS is the correct carburetor for a 67. Check your radiator hose for a spring inside it. If it is missing, replace it with one that has the correct inserted spring. Lack of a spring will allow the hose to suck closed at high speeds due to the vacuum created at the water pump inlet. Any mechanic worth his salt should know this, but Rob's didn't, and that may have been the start of all his problems. Since the overheating occurs only after a long run, I suspect you are loosing coolant while you are driving. Double check all the fittings and connections for evidence of leakage, and don't overlook the heater core(s).  A quick way to check a heater core is to flip on the defroster on the MAX DEF setting for a few minutes on a cool morning - if the windshield fogs up inside, you've got a bad heater core for sure. Also, feel the carpeting for wetness under the air plenum to make sure you don't have a leak inside the car. You might experiment with a coolant recovery bottle for a while, to see if your problem clears up , since the overflow loss will automatically be replaced when the car cools down. If this cures the problem, I suspect you have either a partly plugged radiator or dirty water jackets in the block. You can check for the latter by seeing if the block drains run clean and free. If you have to poke at them to get them to drain, you'll need to remove the soft (AKA core, AKA freeze) plugs and dig out the crud. The best way to check the radiator is to pull it and have it flow checked at a good shop. I assume you have checked to make sure the water pump belt is set at the right tension. A thermostat problem would show up right away, not after 10 hours, most likely. Did you get normal mileage on your trip (15-17 mpg average?) If so, that eliminates a lot of other possibilities.

From PEN:

Permit me to make one point. The most frequent reason for an Imperial to overheat is a clogged radiator. Perhaps individuals did not always run ethylene glycol antifreeze in them. Perhaps they did not add the recommended additives to the coolant. Perhaps they did not follow recommendations in flushing the system. But the number one reason for an Imperial to overheat is a clogged radiator. If that is the case, take the radiator to a professional shop and have it "rodded out." To do that, the radiator will be completely disassembled and reassembled. All the passageways will be cleared. Then, you can start over, with the equivalent of a new radiator. Then follow the factory service manual advice regarding radiator and cooling system maintenance.

Question from Kate (1968):

Today I had the interesting experience of nearly cooking off the 440 in Lucille, my '68 Crown. Cruising in to work at around 70, watching all the early-AM idiots flying by me just so they wouldn't be caught behind that BIG OLD CAR, and I smelled antifreeze - a panic check of gages revealed the temp needle pegged, so I backed out of her a bit and coasted the last 3 miles in at an idle-speed 55 mph. Big time boiling, even in the recovery jug! With a co-worker's headlights for light and a wastebasket of lukewarm water, got her down to a normal temp and shut down with no damage.

This afternoon, she cruised home nicely with radiator cap askew, 60-65 and never even got into the operating range of the temp gage?? Still, I am looking for a radiator as I know this one is getting to the end of its useful life. Can anyone supply info as to whether the '68 used same part number as '66? Son's parts man says his listings end at 66 and start again for 69!


From Demetrios:

Take the radiator to a radiator shop to have it "rodded out". If you buy a used radiator, it may need to be rodded out anyway.

From Dave:

If the rest of you radiator is good, I would highly recommend Performance Radiator in downtown Seattle. It's on Airport Way just south of Dearborn. They have a huge catalog of radiators but out of the upteen for '67 Imperials in the catalog, my particular one wasn't in there, but they recored it for a lot cheaper anyway...looks like new and works great. I was amazed at all the different inlet/outlet configurations the '67 radiator has. My non-aircon/with dual heater radiator wasn't in there.

From Dick:

I had two of these radiators recored (made new again) this past year at a local radiator shop - there was no problem identifying and obtaining the new cores - I had them both within a week.

Question from Kevin (1971):

Today there was a huge puddle of prestone under my '71, but I looked in the cap and only had to put in a little bit. I drove the car around then parked it in a different spot, 3 hours later another huge puddle. I looked to see if there's a leak, but can't find one. I think it might be the hose that spits out onto the ground, but it never spit out that much. Could it be the cap?


From Robin:

Could definitely be the cap. My '72 was losing coolant last fall but not consistently. Replaced the cap and all was well. Until the Autotemp II servo cracked a few weeks ago. But I found another one off of a Mercedes at the junk yard. It is not the aluminum one but at least it does not leak and only cost $10.00.Those heater hoses that run from the firewall to the servo are sure a bear to change. Had to drop the inner fender down to get access to them as they had the old spring clamps on them. Probably original.

From John:

You may just be filling it a bit too full & its seeking its own level. The coolant should be at least an inch below the filler neck when the engine is cold.

Question from Justin (1972):

Since I have bought my imperial about 3 weeks ago I have gone through and noticed that I have no radiator overflow. I have the hose but not the actual overflow. Does anyone know where I could get one, or even a place with the parts (i.e. - junk yard) I have a 72 LeBaron.


From Pete:

Mine never came with one either. A few years ago, I scarfed one out of a '72 in a junkyard. Last year I tried to install it, but I forgot how it originally went in the car. I installed a much smaller one from a 70's Dodge Colt, no less! The more I think about it, the more I think the overflow bottle was NOT stock. I mean, the car I pulled it from had a trailer hitch, electric fan, transmission cooler, etc. I think it might have been added as part of an aftermarket towing package.

From Carmine:

It may have been stock. I believe Mopar started installing them in '71 as a part of the trailer-tow group. I've had two '72 Dodge wagons (one was a parts car) and they both had overflows. As far as the install goes, take the hose that runs from the radiator neck to the ground, and install it into the bottle. Mount the bottle on the radiator yoke, there should be some factory holes.

From Dick:

And, of course you need to change to the coolant overflow system type radiator cap, or else the radiator will not be able to siphon the coolant back up when it cools down.   Everything has to be vacuum tight except the coolant jug itself.   Look through the cap application book at your local auto parts store, that will tell you which is correct for a coolant overflow tank installation.

Question from Stevan (1972):

I have a '72 Imperial lately my temp gauge is reading very high and sometimes pegs out the needle.  Could this be a faulty gauge I have already replaced the sending unit in the engine compartment and I get the same thing.  Has anyone had this problem in the past.  I have also replaced the radiator, hoses and thermostat even replaced the fan with a  new one.


From Dick:

Step one is to get a "candy thermometer" from your nearest house wares department. This is a giant "fever" thermometer, very accurate, and cheap, and reads way higher than you will need. When your car is cool, remove the radiator cap, insert the thermometer, and start your engine. When the temperature stabilizes, you'll see what the actual coolant temperature is, and you can then decide if you have a problem or simply a bad indicator. If the car is actually running hot, see the cooling system checklist for other possibilities.   But don't go down that path until you are sure it is actually running too hot.

From Bill:

Remove your radiator cap and place a candy thermometer or similar tester in the radiator. Start the car and let it warm up to normal temperature, and if it stays around 185 you probably have a bad gauge assuming the wiring is intact.

From John:

If this is the same as '69 & most likely is, there is a voltage limiter in the instrument cluster.

Question from Wayne (1972):

I took Victoria ('72 LeBaron) to check out the "Mopar Mini-Nationals" held over the weekend. (she thinks I should join because in her category, a '72 NEWPORT won and she thinks she could mop the floor with her "competition" next time). Anyway, it was like a gazillion degrees outside, and on the way there and back, although she did not boil over, her heat gauge was at the top of the line, just below the "H". It was especially bad on the freeway at freeway speeds. Like I said, she didn't boil over, nor did the "check gauges" light come on, nor did it make it all the way to "H", but it was hotter than I was comfortable with. I checked her fluid level when cool, and it was full, so, do I have a problem or is it just too d***m hot?

Reply from Dick:

My guess would be that your cooling system is getting close to the margin. When these cars were new, they ran very cool in any weather. My 68 takes a family of 6 to Las Vegas in temps over 115, across the I-15 and in Las Vegas city traffic, with the AC keeping everyone comfortable (only complaint I ever get is from the right front seat, my wife, who likes it warmer than the rest of us, and I have to remind her that her AC outlet is individually controllable as to direction and volume). Under these conditions, the dash gauge never shows more than the first 1/3 of the normal range. My radiator has been rodded out, and I have cleaned out the block passages thoroughly when I was replacing the core plugs. The cooling systems on the 440s are designed with so much extra cooling capacity that they have to get REALLY plugged up before there is any indication on the gauge. Inspect the tops of the tubes with a small flashlight and mirror, you will probably see stuff collected in the top tank You will have to drain enough coolant so you can see the metal "floor" of the tank. If you see crud, then your first and cheapest bet is to pull the radiator yourself, and flush it with copious quantities of water from the garden hose (don't let the water pressure build up in the radiator, though). Be sure to plug off the transmission cooler fittings so you don't get any water in there! The way I do this is: put the cap on, turn the radiator upside down, cover the upper hose connection with one hand (meaning the connection into the "top" tank, which is now on the ground) and fill the radiator by pouring water from the hose into the "bottom" hose connection. When it is full to overflowing, quickly pull your hand off the "top" hose connection and observe what runs out. If you see particles of crud, you've fixed at least part of your problem. Repeat until it runs clean, or dinner time, whichever occurs first. It's a judgment call as to whether or not you've gotten it truly clean enough. If you want to be sure, take it to your local friendly radiator shop and have it "rodded out" and flow checked. If your car only seems to run hot at freeway speed, verify that the spring is still in the lower hose. Many "modern" mechanics don't believe in these, but then they haven't studied physics, usually.

Question from Ed (1981):

While I've owned my '81  for 5 years now, it is carburetor-converted, so I have little experience with with the EFI which is still on my '82 that I bought last year.  Although I live in Florida, I keep this car in Cincinnati as I am based there and commute from Orlando. Now that the warm weather has returned to the Midwest, so have my car's troubles: When the car is cold and the ambient temp. is cold, he runs great.  Even with the warm weather now in place, the car starts right up when the motor is cold. However, once warmed up, the motor idles unevenly and stalls.   This past week, I could not even get it restarted and had to call AAA for a tow. The problem is that since, I don't live there full-time, I have not been able to find a shop to work on the EFI (a problem all 81-83 owners are familiar with). Also, since my home is in Florida, I only have limited tools and equipment in Cincinnati to work on the car.  Ideally I will find a Chrysler dealer with the original test equipment in the area, but any help in troubleshooting on my own would be greatly appreciated. I've recently changed all of the filters, plugs, wires, cap & rotor, oxygen sensor, and some leaking vacuum lines. There is a considerable amount of dirt and dust accumulations under the hood, and I plan to clean up all of the connections with electrical contact cleaner as well, but I really don't expect that to correct the problem. Has anyone got a hint as to where I should begin my troubleshooting?? 

Reply from Dick:

Your problem sounds like a failed or disconnected EFI coolant sensor. This is the sensor that has a two wire connector, with the connection arranged in an "L" shape. It is located just to the left of the water outlet connection to the radiator hose on the top of the intake manifold, at the front left-hand (Drivers side) of the engine. The connector will pull off fairly easily. The sensor is an odd size, and I would recommend being armed with a deep, thinwall socket that fits very well, and a breaker bar or large drive ratchet so you can get it out without too much drama. Since it threads into the water jacket, you will lose coolant while you are changing it, so be prepared for that, and have the new one at the ready. 

If you have access to a VOM, you might want to just check it before you go to all this trouble, it might not be the problem's cause. To check it, remove the connector from it, and measure the resistance between the two copper prongs on the sensor, you should get a reading of around 900 to 1000 Ohms with the engine cold, and much higher with the engine up to operating temp, in the 2000 to 3000 OHM range. There should be no contact to the engine ground (Very high resistance, over 100,000OHMs.) If resistance you measure is in this range, this is not your problem, so save your money. In that case, check carefully the connector and the wires in the harness to make sure you are getting a good connection.

IML member Carl Baty discovered that NAPA carries a close equivalent, which I believe he is using successfully in his San Diego car, so it is close enough that it will get you from cold start to medium warm temperatures, if not the whole range. I believe he said it was their part no. TS 5008. They also should have a socket to use when removing it, such are specially made for sensors and senders and switches, about the size and shape that a regular 12 point will fit, but not too well. I forget at the moment whether it is a 1" or 1 1/16" that fits it fairly well, but the special socket is the one to have in your tool box for many uses. Mine is 1/2" drive. I did have a problem with one of the sensors being so corroded into its hole that it twisted apart when trying to remove it, and had to be picked out in pieces. Not fun. 

Chrysler dealers with a helpful counter man can also look it up in their part finder system, I was able to find two on the shelf at a dealer in northern CA, but when received, one had been opened and did not work, the other one is fine. They get $40 apiece for them, and there are no refunds on bad electrical parts, so I got stuck. The NAPA sensor is much cheaper, and readily available, so I would try that.

Question from Jack (1981): 

One question..... I noticed that my coolant level gradually decreases, and can find no evidence of external leaks. I've replaced all the hoses, and driven about 4k miles since. I'm sure I've completely filled the system... There's no evidence of oil/water mixing, and I do sometimes get a whiff of hot antifreeze, but no visible leak.  I've added perhaps a couple of quarts in the 4k miles...... Any thoughts?


From Dick:

Question one is: is your coolant recovery system intact?

Question two is: is your radiator cap the correct one, and is it new or are you certain that it is sealing tightly around the outer neck? To determine that all is OK here, note a couple of things:

1. When you check the radiator contents at the cap, is the top tank always completely full (which is measured at 2" below the cap) when cold? (It should be.) If you have lost enough coolant that the level is down here, is the coolant recovery tank empty? (Under these conditions, it should be.) 

2. When you have topped up the system, (top of radiator full and the level in the recovery tank at the "cold" mark), start the engine and watch the level in the recovery tank. After a while (like 30 minutes), the level in the recovery tank should have gone up, and the fluid should be warm in the tank. Then turn the car off and let it cool for an hour or so. The level in the recovery tank should go back to where it was when you started, and the top tank of the radiator should still be full. If both of these answers are yes, then I would recommend you take it to a cooling system pro and have him perform a test for exhaust gases in the coolant. This is a cheap, easy, and very definitive test of your head gaskets. Also, inspect the area under the heater core to make sure you don't have seepage into your carpet or sound deadening material.

From Norm:

Check your radiator cap.  If it is old it may not want to hold the 16 or so pounds required to keep the antifreeze from boiling over when the engine is shut down hot. Been there, done that and cured the problem.

From Marcus:

Also, check your heater core for leaks.  The coolant is going into your carpet.  My 67 did the same thing.   It is a very slow leak in the winter, getting worse in the summer. You may also see a small wisp of vapor coming from your a/c vents.

Question from Rob (1982):

It turns out that all day yesterday she was running over-hot, and losing  coolant (I couldn't tell because the new voltage regulator I got is screwy,  it makes the gauges fluctuate too much to get a true reading, and we were traveling fast enough not to notice any steam coming from under the car). I poured two gallons of anti-freeze and two gallons of water into her before she got back to level. YIKES!!!! That's a loss of a full quarter coolant capacity. Man, that could have been BAD. No wonder tonight she overheated immediately. I'm just glad I was paying attention today, and that we made it home yesterday.  Any ideas?


From Brett:

I wouldn't get all worked up about this. Take it one step at a time. The cooling system's pretty basic and now you've learned that when you go to the trouble and expense of putting in a new radiator it's not a bad idea to replace the thermostat too. (My lesson cost me a $400 towing bill from Gainesville to Delray Beach, FL) If the car has air conditioning a new fan clutch is also a good idea. A new water pump is even more piece of mind. (Notice how I mention the cheapest "insurance" first and so on.) Your last step it tracking down a cooling problem would be a bad head gasket (water can show up in your oil when this happens I think)... but go through all the other steps first. (Shady and inexperienced mechanics like to get you thinking about the head gaskets right away.) Anytime you replace something on an old car you need to ask yourself what other related parts could also be affected and consider replacing them as you budget allows. People usually apply this practice with brakes and forget on the other important systems like fuel (pump, filter and carburetor), cooling (radiator, thermostat and pump), electrical (alternator/generator and regulator)... you get the idea. I doubt engine crud is contributing to a temperature problem. I've owned a bunch of 413's with all sorts of miles on them and never had much problem until they start getting smoky. So if your exhaust is clean and the oil breather cap isn't chugging out fumes I'd consider some detergent oil (or some engine cleaning additive) combined with some frequent oil changes. When the used oil is coming out smooth and without clumps I'd return to regular maintenance.

From Ken:

Or visa versa, or exhaust bubbles in the water, or neither if two cylinders are just leaking combustion into one another. Do a compression check to be sure.

Follow-up from Dick:

Best way to check for exhaust gasses in the cooling system is with a special detector that almost any radiator shop will have (they are cheap, I bought one for under $50 and you have to replenish the detector fluid once a year or so for around $10). These detect even a minuscule leak from the combustion chamber into the cooling system. Ken's suggestion of a compression check is a good idea! You'll learn a lot about your engine, especially if you have them do a leak down test at the same time (to see where you are losing compression, if you are, that is.)

This page last updated October 12, 2004.  Send us your feedback, and come join the Imperial Mailing List - Online Car Club