Diagnosis and Repair of Your Imperial's Engine Noises


Imperial Homepage -> Repair -> Engine -> Engine Noises

Tip from Brooke:

Sometimes, a carbon knock will sound just like a rod knock. It will sound like it's ready to throw a rod. I can't even count how many times I have fixed this with about half a bottle of transmission fluid.

Start the engine; remove the air cleaner; rev the engine up to about 2500 rpm and start slowly pouring the transmission fluid down the carburetor throat. Don't let the engine die. (if it does, you might have to pull & clean the plugs, then resume the procedure). Pour the XMF fast enough to lug the engine down.

Voila -- no more knock. Gone for good. This apparently happens when a little piece of carbon breaks off inside one of the cylinders or something..... but I've fixed 'em numerous times this way when I thought I had lost a rod bearing.

Tip on diagnosing engine noises:

You or someone you hire, must find the noise before you can fix it. If it is an engine noise, it could be a bad lifter, a broken valve spring, a bad rocker, a loose valve guide, a bad oil pump or a bad oil pump pressure relief valve, a bad cam bearing, a bad crank or main bearing can all cause noises in the valve train. But some very unusual noises can be caused by bad harmonic balancers, broken flex-plates, bad water pumps and alternators bearings, bad fan clutches, blower motors, A/C compressors and believe it or not, paper stuck in the grill.

A good tech will perform a bunch of tests to determine what makes the noise come and go. The tech may test drive the car if the noise is related to brake application or steering input. If the noise is an engine noise the tech may kill each cylinder one at a time and listen to the noise and see if it changes. If it does, the tech will know which cylinder is a part of the noise and of course, which ones aren't. We often use a stethoscope to find the area of the engine the noise is coming from.

Once the noise is isolated to a particular part of the engine, transmission or rear end, the next step is to take an oil sample and look at it or have it analyzed. Sometimes you can see the metal in the oil and sometimes you can't but a local oil lab can see what kind of metal is in the oil. Aluminum typically comes from the pistons, brass and lead from the bearings or the radiator, steel from the crankshaft and often times water or coolant will be found which will tell us a coolant leak either started the problem or was caused by the problem.

It is very important to find the true cause of the failed lifter or failed bearing because their failure is almost always caused by something else.

The most important thing is to make sure you are working on the right noise. I can't tell you how many times a transmission was overhauled because the driver thought the transmission was stuck in second gear when the fan clutch was locked up. Broken flex-plates or flywheels sound EXACTLY like a bad rod or main bearings and the two are very hard to separate. The difference between the two is when the symptoms occur and what makes them come and go.

Knowing that, you see how important it is that the driver clearly tell the shop how and what makes the noise occur and what makes it go away. The drivers involvement is critical when hunting down a noise. And the good news. Sometimes a huge piece of carbon will break loose from the EGR passageway or from a valve and it will end up sitting on top of a piston. It will make a huge knocking noise, a noise so loud and so bad that everyone who hears it will think the engine is going to blow up any minute.

We can dribble ATF or water into the engine through the carburetor or the fuel injection throttle blades and cure that "knock" in one minute and at a cost of $25-60. I learned this years ago when we diagnosed a knock as a bad engine and the customer went to another shop and they decarbonized the engine and cured the knock. You can imagine how mad the customer was when they came back to us to tell us that they got the knock fixed for $60 not the $4,000 we had bid the repair for. So as you can see, noises are sometimes very difficult to pinpoint.

So when you have an engine noise, check or change the related fluid and do your best to find out what makes the noise come and go and which portion of the engine it seems to be coming from.

Here's a few words we recognize as noises and what usually cause them:

Bang -- Backfire caused by spark misfire or lean condition
Boom -- RWD drive shaft or u-joint problem
Buzz -- Bad interior trim part fit caused by wind
Chirp -- Belt related
Clack -- Engine / valve train related
Clang -- Heard through the drive shaft on RWD car
Clank -- Heard through the drive shaft
Click -- Engine / valve train related
Clunk -- Suspension related
Flapping -- Belt related
Grinding -- Brake related
Groan -- Suspension related
Grunt -- Brake or suspension related
Hiss -- Cooling system leak
Hum -- Bearing, rpm related, a/c related
Knock -- Engine related
Ping -- Caused by engine, fuel, timing, carbon
Pop -- Backfire
Rattle -- Exhaust system related
Roar -- Bad fan clutch, tire noise, muffler, transmission
Rumble -- Muffler, tire
Scraping -- Something moving and touching
Screech -- Brakes or belts
Sizzling -- Something burning, coolant/oil leak
Squeal -- Brakes or belts
Tap -- Engine / valve train related
Thump -- Suspension related
Whine -- Bearings, bad gear alignment
Whir -- Probably nothing to worry about
Whistle -- Air leaks, door gaskets, etc.

Another great reference written by Dave from Reman Engines:

First thing you need to do is spend 20 bucks for a cheap stethoscope at the auto parts store or if you are going to do this a lot get the electronic ones from Hepp.

But, possessing human nature, you will convince yourself that a hose stuck in your uneducated ear will do just as well. No sense in arguing with you that the whole idea is to be able to discern infinitesimal changes in direction and intensity that require the use of two somewhat experienced ears AND the right tools.

So stick your dumb ol' hose in your stupid ol' ear and we'll start with some clues.

Remember that diagnosis of engine noises is nothing more than splitting possibilities down to only one

First off, eliminate all of the accessories like the alternator, power steering pump, A. C. compressor and vacuum pump by removing the belts one at a time. If the noise is gone, of course the problem is a belt driven accessory. If the naughty noise is still there you should be able to hear it more clearly by not having the accessories whirring away

If the engine has a carburetor instead of fuel injection it probably has a mechanical fuel pump mounted to the engine. Before the engine gets too hot, put your hand on it. If it is making a noise you should be able to feel it.

Try to track the noise down with the stethoscope tip or the end of the hose suckered onto the engine surface, sealing the end. Spend a full ten minutes putting the hose all over the engine, not just where it is loudest. Try to envision the parts moving inside the engine. You are training your ear, not just listening, so don't get in a big rush except to be sure that the engine doesn't overheat. A trained ear can tell you which piston is slapping or which rocker arm is clacking from outside the engine so if you come out from under the car proudly saying, "it's the bottom end" get your dumb-ass back under there until you can tell me it's coming from the oil pump or the 3rd piston back on the driver's side or the flywheel or the camshaft.

Rod knocks are loudest at higher speeds (over 2500 RPM) Feathering the gas pedal may result in a distinctive back rattle between 2500 and 3500 RPMs.

Bad rod knocks may double knock if enough rod bearing material has been worn away allowing the piston to whack the cylinder head in addition to the big end of the connecting rod banging on the crankshaft rod journal. It will sound like a hard metallic knock (rod) with an alternating and somewhat muffled aluminum (piston) klock sound.

Determining which cylinder contains the noisy parts may be aided by shorting out the plug wires one by one with a common low voltage test light. Now you won't get the bulb to light up but it is a convenient way to short the cylinders without getting zapped or damaging the ignition coil.  Attach the alligator clip to a convenient ground, away from fuel system components, and pierce the wire boots at the coilpack  or distributor end of the wire.  If the noise is changed when the plug wire is shorted to ground, you can figure that the problem is in the reciprocating bottom end parts. (piston, wrist pin, connecting rod or connecting rod bearing)  The reason the sound changes is that when you short the cylinder plug wire you are stopping the combustion chamber explosions that are slamming the piston downward making the inside of the big end of the connecting rod bang against it's connecting rod journal. Or in the case of piston slap, no explosion changes how the piston is shoved hard sideways against the cylinder wall.

If you get a change in the sound when you short a cylinder out it may become moot as to what the problem is because the oil pan and cylinder head must be removed to correct the problem. [Generally speaking, an engine with damage to reciprocating parts (pistons, rings, connecting rods, wrist pins or rod bearings) and more than 70 thousand miles is not cost effective or risk free enough to attempt to repair. Replacing a crankshaft, for example while the rest of the engine has 70k perfectly maintained miles on it is risky enough but whatever killed the crank has scored the rings and packed the lifters with debris and smoked the piston pin bosses etc.]

If the sound doesn't change, look at parts other than the reciprocating ones. In many cases of rod-knock or piston slap, more than one is banging so even if you eliminate the noise from one rod the other one will still be a-banging away with a different, more singular tone.

There is a real nice yet little known test for piston slap I'll pass along. Some test results can be mixed or ambiguous but this one is 100% and I've never seen it wrong after using it for the last 10 years.

When the engine is cold, the aluminum piston is small in comparison to it's iron cylinder. Therefore the rather hollow slapping noise will be loudest first thing in the morning. After the engine warms up, the aluminum piston heats up faster than it's iron cylinder, cutting down on the excessive clearance between the piston and cylinder wall.
So, the test is this:
First thing in the morning, start the engine up and run it for 15 seconds while you listen carefully and memorize the sound and it's intensity. Shut it down quickly, pull the spark plugs and put two squirts of motor oil into each cylinder. Reinstall the plugs, fire the engine up again and listen.
If you have piston slap the noise will have been greatly reduced or even eliminated…..for 15 or 20 seconds that is, and then your nightmare noise will come back.

Valve train noises generally are loudest up to 1500 rpms. Lifters are also misdiagnosed commonly as the source of many noises when in reality they are quite trouble free. Dirt contamination on a sludged engine is the number one cause of true lifter noises, low oil pressure is number two, . Whatever you do, don't put engine flush in a sludged engine! We call it "Instant rod knock" because of the way it overloads the oil filter to the point of opening the filter bypass valve, flooding and destroying the engine bearings with mud. The only safe way to clean a sludged engine is to accelerate the oil changes and let the detergent in the oil do the cleaning at a controlled rate. Like every 500 miles

By the way, if you have low oil pressure, don't bother putzing around with the valve train because the damage you find will be the result of low oil pressure and will return after you spend a bunch of money on valve train parts.

Over nineteen engines out of twenty that we tear down with low oil pressure do NOT have bad oil pumps but have worn out bearings and journals so quit with the wishful thinking about just putting a pump in it.   Think about it, usually,  an oil pump is two dumb ol' iron gears spinning around immersed completely in oil. EVERYTHING else in the engine has a tougher time of it than the oil pump.  Worn camshafts, low oil pressure, worn rocker pivots, very loose valve guides, worn rocker arms…..

Question from Dan (318):

I was finally able to take my 83 out for a spin Friday!!  Here's what happened. It started right up, and I let her idle for a couple of minutes. 

The last time I ran it, I noticed a slight 'ticking' noise but it went away.

So, on my drive Friday things went fine at first. I took her out on the highway and cruised for about 3 miles, and then turned around. On the way back I decided that I would give it the gas and stepped on it. I noticed the usual blackish cloud out the back but she took right off.

Then, just a quarter mile from home the oil light started to flicker on, slowly getting stronger until it finally stayed on as I coasted into the driveway. I could here that 'ticking' noise again, so I shut it off.

I checked for obvious leaks - none. I checked the oil level- fine.

I started it up again, and the ticking was there but the oil light did not come on. I used the old 'broomstick to the ear' trick and tried different spots around the engine until I could hear the ticking at the right front on the valve cover. As I was listening, the ticking faded away and she was running smooth.

So, I pulled out onto the road, and no problem. I went down the street and then stopped and let it idle. No ticking, no oil light. I turned around and gave it the gas again.

Sure enough the ticking came back and the light flickered back on.

HELP. I looked in the FSM. One possible cause is a clogged oil filter. Could it be that simple?

I sure hope it's not major, as I have never done any major engine work.

Any ideas? (I will probably change the oil and filter ASAP anyway.)


From Dick:

The ticking is a sure sign of inadequate oil pressure, as you probably realize. Depending on the mileage on this engine, it may be time for a lower end rebuild, but before you do that, remove the oil filter adapter and clean the bejabbers out of everything you can see from there. Change the oil to straight SAE 30W (not 10W30 and especially not 5W30!). Buy a WIX or NAPA (not "Silverline, get their best grade) oil filter and install it. This may get you down the road for a few more miles, but my crystal ball tells me there is a pan dropping in your future!

It is possible that your oil pressure relief valve is sticking open, but to find out about it you have to remove it and inspect it. You might as well check the oil pump and bearings at the same time.

From John:

The most common thing is the oil sending switch. Not hard to change. If that's not the problem, you may have a weak or clogged oil pump.

From Kerry:

Change the oil and filter to be sure. I hate idiot lights. While troubleshooting, put on an aftermarket oil guage that gives you an analog actual pressure reading. That will tell you what is really going on. They are cheap.

Question from Kerry:

Is there a definitive way to tell the difference between a clicking lifter and an exhaust leak from a cracked exhaust manifold?

Been down the road of replacing lifters only to find it was a cracked manifold once before.


From Jim:

If the lifters are hydraulic, the clicking should cease once oil pressure has built up to take the slack out of the valve train. If it's an exhaust manifold leak, the clicking will always be there.

From Allan:

The best tool that I ever found for this and other noises is an electronic stethoscope, usually available from a parts store for around $30.00, in lieu of that, you can remove the valve covers and use the old finger method of touching the rocker arm with your finger to feel for the shock of the lifter hitting or use a thin steel rod or vacuum hose to your ear and the rocker. Makes one heck of a mess though.

From Dick:

use a stethoscope, but a short length (3 feet?) of rubber garden hose works almost as well. If you have a cracked manifold, you can home right in on the crack with the hose by blocking one ear and listening to the other end of the hose. There will be no doubt, because you'll hear the puff of air each time the closest cylinder fires. Also, the manifold crack tends to get less as the engine warms up, it is worst when ice cold.

From Phil:

A mechanic's stethoscope, with a probe , should do the trick. Also, sometimes if you wave your hand, Carefully! around the exhaust manifold at idle, if you got a leak, you can feel the exhaust coming out. The real fun comes in when you have a lifter ticking and an exhaust leak!

From Leo:

A cheap way to check is with a length of broom handle. Hold one end to your ear and the other end on the valve covers in different spots.

From Steve:

Yes, an exhaust leak will increase/be louder when the engine is put under load. A "ticking" lifters' noise will remain constant under load.

Have someone sit in the car with their foot on the brake...and have them step on the gas-pedal a little while you listen underhood.

From Kenyon:

For mine, the exhaust guy had on gloves and ran his hands around the manifolds/pipe mating joints. When he felt airflow, he had found the leak via the pulsing exhaust leaking out. This was while I was in the car holding it at 3k RPM.

Leak on mine was at the pipe/manifold joining flange.

Not a good technique if the crack is on the underside of the manifold next to the block, but that's not the stressed area, for the most part, and I think the metal's thicker there, anyway.

Gloves used were finely knit (cotton, wool?) and may have been specific to welding, but not air-proof rubber or something like that.

From Bob:

Before you do anything else, check around your heat damper.  This is where I found mine one time but I did what you have done and felt like a fool when it was that.  The heat damper had rusted out and this left 2 holes in the exterior where the heat damper was.

Question from Canu (413):

The warmer the '62 engine gets, the worse the noise. Despite high octane gas and occasional lead additive the clatter persists without relief. It sounds like the valves are making the noise. If so, what is the cure? Are parts avail.? How much to fix?


From Phil:

I'm curious, have you tried retarding the ignition timing to see if the problem decreases? Also, sometimes on an older vehicle, the outer ring on the dampener will rotate, making it impossible to set the timing correctly by the timing marks. How is the oil pressure on the vehicle? Lifter noise can make just as loud a racket as preignition, maybe more so, and the description of the noise getting worse as the engine warms seems valid, because oil pressure usually drops on a worn engine as temperature increases. Something else must be extremely out of adjustment somewhere, cause usually high octane gas will do the trick.

From Dick:

Unless you know that the noise is from pre-ignition knock (in which case you need to retard your timing to fix it, before you burn out a piston top), you may have extremely low oil pressure, which also will destroy your engine quickly if you continue to drive it that way. You need to find out what the cause is, before anyone can estimate what it will cost to fix. If it is simply pre-ignition, you should be able to make the noise go away and drive the car safely at no cost, by simply retarding the timing.

Parts are available to fix this engine at any parts store. You can order a complete rebuild kit from NAPA and many other sources - all parts are readily available.

A major rebuild can cost over $2000, unless you do most of the work yourself, and even then it will come close to $1200 if you have to have the machine work done by a vendor, and you want it done right. Parts alone will cost over $500 for a complete rebuild. But, your engine may not need a "complete" rebuild - you just have to have someone who knows what he is doing evaluate it. My advice is to follow the steps below:

Step one is to look at the oil pressure gauge and make sure it is working right and reading adequate pressure, to learn about the condition of your oil pump and bearings. Don't drive it any more until you do this! If the oil pressure is very low or non-existent, shut off the engine and start saving your money for a rebuild.

Step two is to evaluate the timing and other tune-up settings, in case this is a simple mis-adjustment problem. If you can fix it by retarding the timing, just drive it that way - you aren't hurting the engine by using it this way.

The next two steps are not directly related to the noise you are hearing (probably), but the answers are needed to evaluate what needs to be done to make it right again.

Step three is to do a compression test, a power balance test, and a leak down test, to investigate the condition of the rings and valves.

Step four is to check for timing chain wear (see how far you can rock the crankshaft without seeing motion from the distributor rotor). If it is more than 2 degrees, your engine timing hardware is worn - if it is more than 4 degrees, it is worn out!

Once you know the answers to these questions, you will be in position to estimate the repair cost, or have someone help you figure it out.

From Joe:

Make sure it's not the heat riser valve. It's located on the passenger side exhaust manifold and operates by a spring. My newly acquired 63 has this problem and sounds like all hell when it starts. If the noise goes away with more RPM and comes back when the engine goes back to idle it is more than likely the valve. My mechanic tells me this device is to help the engine warm up quicker. I believe the spring can't be replaced or can be locked in the open position.

Question from Johan (413):

I've got some occasional knocking in one of my valves from starting the engine (1965-413) with the petal all the way to the floor (BAAAAROOOOOMM tick tick tick tick...."woops-darn it!").  I had a hard to startup at one time, from one of those fuel additives a while back that has since gone away. Blowing a small amount of gray smoke when I accelerate hard too. Again the noise is only occasional and when I accelerate hard. possibly a lifter. Is this hard to remedy? Costly at the garage? Am I correct in the diagnosis?

Reply from Dick:

The lifters don't know what you are doing with the accelerator. If the noise is dependent on accelerator position, the chances are this is either a pre-ignition noise or a more serious mechanical problem. Try retarding the spark timing about 5 degrees to see if it goes away - if it does, relax. If it doesn't, start saving your pennies, it's probably a rod bearing.

The right way to start a cold MOPAR of this era is to press down the accelerator pedal about 1/2 way one time to "set" the choke, then release it, and crank the engine. If all is in good shape, the engine will start and idle without further touching of the gas pedal. This procedure is clearly stated in your owner's manual, also.

Question from Canus (413):

At idle everyone can hear my '62 Imperial rattle and make an odd sound coming from the fan. It sounds like bearings going. Can this be with only 35K miles? The fan seems loose but the belt is tight. Loose in a way that if wiggled, there is a fair amount of play. What can I do to fix this noise?


From Tim:

Sounds like maybe your water pump.

From Russell:

Sounds like a bad water pump. If you can turn the fan clutch fairly easy and it feels smooth to turn, it is probably the water pump bearings. You would have to replace the pump.

From John:

It sure sounds like a bad pump. If you have play in the fan when you wiggle it forward towards the engine and backwards to you. The water pump is the problem. Sounds like a roller coaster when they get real bad.

From Gene:

You also might check to be sure that fan clutch bearing is not the culprit. My 65 had somewhat the same symptom. It was the fan clutch bearing. While wiggling the end of the blades, the blade tips moved about half an inch. . A new fan clutch solved the problem. Even if it is the pump, be sure to check the clutch also. Might save a fan blade from going through the radiator.

From Paul:

Well, I can tell you one thing, if you don't fix it, you will have a lot more work to do if the fan flies off into the radiator. Low miles doesn't mean no repairs. As others have already said, the water pump is probably going out. If the fan is loose, it has probably gone out.

I once knew a woman who had a '64 New Yorker and didn't know that the fan was about to come off. The water pump never leaked, and she didn't know anything was wrong. When it came off she was entering a freeway and accelerating to merge. Needless to say she didn't actually make it onto the freeway, and pulled over to the shoulder.

The damages totaled the car. Among other things, the radiator was destroyed, the power steering pump, alternator, upper, and lower hoses, the fan itself, the hood was dented and the battery was fractured.

I would recommend that you not drive your car until you fix this problem.

Question from Johan (413):

I have always (about 6 months) had a slight "clicking" on the passengers side possibly #4 cyl. when idling. Not loud or annoying, but noticeable with the hood up. I get a much louder "diesel like clacking" when wide open, say getting on the expressway but not "kicked down" yet.

Local "old car guy" mechanic says its not much to worry about. Is he right?

I just heard from a local "young car guy" that it can lead to valve train problems or worse. I'm all confused man! 413s are pretty straight forward aren't they?

All I'm looking at is a "dry" lifter right?


From Kerry:

Sounds like EITHER a collapsed lifter or a bad exhaust leak. The lifter can eventually cause serious problems in the head and if its completely collapsed you've pretty much lost that cylinder. The exhaust leak can be a problem IF it's between the head and the manifold. Eventually there will be erosion of the head or manifold or both because of the hot exhaust gases blowing out.

I'd try and deal with it.

From Dick:

As Kerry says, this could well be an exhaust leak. The lifter doesn't care what load is on the engine, it wouldn't get louder at higher RPM. In fact, if it is leaking down, it will probably get quieter at higher RPM.

From Mikey:

There was a post about a clackety clack noise from someones car...and this was possibly diagnosed as either a lifter problem or exhaust noise. If this was on a 413, dont forget that the rocker shafts on those older engines were bolted down on a separate pedestal, not a cast in pedestal like on the later big blocks. I had one of those thru bolts that hold the pedestal down get a bit loose.....instant clackety clack noise you would have sworn a lifter collapsed if you had heard it. It may be worth pulling a valve cover and checking those bolts just in case!

This page last updated March 17, 2004.  Send us your feedback, and come join the Imperial Mailing List - Online Car Club