Cleaning Your Engine Compartment


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From Robert:

I once wasted my money having the repair shop do a steam clean. They didn't screw anything up, but it's a real easy do-it-yourself. I like to use Gunk engine degreaser (white can) for the heavy duty work and sometimes use Gunk foamy engine brite (blue can) for routine clean up. Spray it on, let it soak, hose it off. Repeat as needed. Take the air cleaner off, use aluminum foil to cover the top of the carburetor, and the distributor. No need to get carried away making it airtight, just enough to keep the water out. If you're in the commercial car wash, avoid using the high pressure rinse near wiring, vacuum hoses, etc. It's been my experience that high pressure rinsing doesn't really remove any more grease, grime, and dirt than normal pressure rinsing. To get the accumulated gunk off the frame, lower engine, trans, floor pans, etc the best bet it to SOAK it with degreaser and let it sit for an hour before rinsing. Aside from being nicer to look at and less agitating to work on, a freshly cleaned engine compartment is a great way to figure out where the leaks are really coming from. As for no start or rough idle after a cleaning, I've never given myself a no start condition, but I can imagine it if you get carried away with the rinse cycle. Keep the water away from the carburetor, distributor, and relays. Keep the pressure down when rinsing the wiring. Rough idle after a good cleaning is dependent on engine temp, air temp, rinse water temp, engine sealing and state of the wiring. The temp considerations generally amount to the thermostatic choke getting 'confused'. Temp and sealing add-up to moisture in the carburetor and/or in wiring connections. If your car runs rough on wet or humid days it will run rough after a good cleaning. Just crank it up and let it idle until it dries out.

From Mike:

If you are having problems with your car starting after you have cleaned it, try and spray a can of "Ignition Dry-Out" spray! Bought at any local parts store, you spray this stuff all over the spark plug wires. I guess that it's non-conductive (?), and eliminates arcing. 

From Greg:

To clean engines, I spray on diesel oil, let it sit, then wire brush the most stubborn crud. Most of the crud comes off with the first application of the diesel. To get the residual diesel oil off, I then spray the engine with solvent. Let the engine air dry after application because solvent is combustible. I use large sheets of card board under my lift to catch the crud and when they get dirty I replace with new. It works well for me.

I don't like to use any water or sand blasting near or around my engine, there are just too many parts that can be affected or damaged. I watched a guy clean a big radial airplane engine with a water hose and detergent, after he finished the job the engine wouldn't run. He had inadvertently got water into the magneto, which now required a tear down and cleaning. My neighbor had an engine for his Dodge minivan rebuilt by professional mechanics. After about 4,000 mile the engine lose oil pressure. Upon tare down he determined that the "professionals" has sand blasted the valve covers during the cleaning process. The sand had become trapped inside the valve cover baffles and gradually worked its way into the engine bearings. A complete rebuild was needed and my neighbor had to threaten the mechanics with a law suit to get justice. I like to use petroleum based products like diesel and solvent for engine cleaning, keep the pressure washers for the outside of the cars body.

From Zub:

I have found the local co-op store has their own brand of household grease cutter. A very large bottle of this yellowish greenish cheap cleaner, 1 liter is a $1.50 or so. It works wonders. It even washes the grease off with cold water. Its made for the home so the paint stays put.

From Bob:

Everyone is cleaning their engine for the upcoming shows, right? I just tried a new product, on the recommendation of my local (small) parts store - Castrol Super Clean. The label says "3 times stronger than Simple Green". I was a little put off because they only had it in gallon jugs - about $9. Anyway, it worked well on a grungy Toyota engine (not my car!) and didn't tear up my hands too much - all my rubber gloves have melted. I used it both in a spray bottle & with a brush - cuts the grease and washes off with little residue. Didn't even use a quart, so there's enough for the 440 - is isn't very dirty anyway.  This cleaner also works well on carpets.

From Mark:

Go to your local auto parts store, buy a can of Gunk engine degreaser, mix it up with a liberal amount of old engine oil, and squirt some right in your eye! I hate it when that happens. No, seriously, folks, for those of you who are considering cleaning under your engine, get a pair of safety goggles that wrap ALL THE WAY AROUND the sides of your eyes. I made the (stupid) mistake of using some that I use for other purposes that do not wrap completely around, and a little drop of degreaser/oil found its way into my eye - almost! Enough to burn pretty good. Not fun!

Question from Greg:

The shop that is currently finding the leak in the a/c on my '61, also does steam cleaning of engines. Is steam cleaning engine area a good idea or will it do more harm than good on already brittle wires, etc.?


From Dick:

I have both a pressure washer and a steam cleaner. The steam is much more effective for old crusty crud and congealed grease, but it is very hard on painted surfaces (peels off the paint) and will find its way into anything, no matter how hard you try to seal it up, so if you drive it into the steam cleaner, I'll bet you a buck that will be the last time you drive it for a while. (Everything, I mean everything, will have moisture and condensation in it!). You'll also want to be prepared to repaint everything under the hood, and replace all the decals. After the mid-50's, the wires are pretty tough, although you may lose the harness wrapping. Earlier cloth covered wire will disintegrate to bare copper and shreds of cloth wrapping. Even the better pressure washers (say over 1500 PSI, heated 200 degree water with detergent) will produce some of the same problems. The toy ones they have in the "quarter in the slot" places are usually not too aggressive, and while you will also probably have trouble getting it to run again afterward if you wash the engine, at least it won't do any permanent damage. I'd recommend a mild pressure washer for the engine compartment, and then if you are willing to get under the car with a can of black "Rust-O-Leum" after it's done, have the chassis steam cleaned. If you are just going to let it rust after cleaning, better let it be, the grease, tar and remaining undercoat is protecting the metal under there.

From Lee:

I've had a number of old engines cleaned at the local car wash [they call it steam cleaning but I'm pretty sure no one uses steam anymore...just water] and never had a problem. Just make sure they cover all the parts that can be damaged from the water. It does a decent job of removing just enough grime so you can see how really filthy the engine compartment has gotten.

From Bob:

I took my '66 in for steam cleaning about 4 years ago - the advertised cost was $35. They offered to do the whole chassis for $45, so I had it done and nothing strange has happened since then.

From Bill:

I personally wouldn't do it on that old a car, they like tender loving care.

From Steve:

While working on aircraft all day, when it comes time to "de-grease" an engine we use mineral spirits and compressed air. Snap-on makes a tool that is merely a blow-gun with a clear plastic hose which gets submerged in a 5 gallon jug of mineral spirits. The suction of the outgoing air draws the spirits up the hose and out with the air. Just make sure to catch all the drippings in a pan or with plenty of rags. Any spirits left on the engine evaporate in about 10 minutes.

This page last updated September 28, 2001.  Send us your feedback, and come join the Imperial Mailing List - Online Car Club