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Hagerty Employee

3 dos and don'ts for cleaning your engine compartment

The fit and finish of a car's exterior often gets all the attention, and most gearheads will debate polishes and paint protectants for hours on end. If you want to find who is really detail-oriented at a car show, don't look at the hood—look under the hood. A spotless engine bay is tough to achieve and even harder to maintain. It's worth it, though, because a clean engine compartment is not only attractive but also conducive to spotting any leaks or issues when they start, rather than leaving them to be camouflaged by grime.


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Intermediate Driver

WD 40 is a kerosene based cleaner and leaves a residue of protectant on surfaces that are cleaned by it. Owing to the kerosene (oil) it is a mild lubricant as well as a solvent. Very useful for a multitude of applications.


I sell industrial cleaning chemicals for a living, and I think I can add some constructive comments to this.

 Absolutely use an OIL BASED cleaner/lubricant (penetrant etc.) to loosen oil based contaminants (crud). We sell one that is essentially a highly refined mineral oil,  and it is an amazing way to start.

 WD-40 is OK, but beware, it is basically diesel fuel (check the SDS, I'm not kidding:diesel)

Then, follow up with good, ALKALINE, water based cleaner/degreaser (like 409, simple green etc.) to remove the (more) liquid "crud" (liquified by the oil based penetrant product) -OR- a SOLVENT BASED cleaner like Brakleen etc., same process, but pay attention to these: Flammable AND Toxic

 Citrus cleaners can be deceiving: the REAL ones use a natural solvent called di-limonin, and found in citrus peels. These work like solvents, but can harm painted finishes, rubber, plastic etc. These Di-limonene based producte are used to remove adhesives, tar etc., and basically a solvent that doesn't evaporate quickly, (it's more oily) The FAKE "orange cleaners" are cheaper, and are just an ALKALINE based cleaner degreaser, with an orange scent....make sure you know which one you have. 


A couple of repetitive spray cleanings with Purple Power and a garden hose rinsing on all my vehicles has done me well when cleaning an engine bay. If the engine bay is excessively dirty in places, I spray the Purple Power on the area, let it sit for several minutes, scrub it with a bristle brush or old toothbrush and then rinse it off. 

Usually don't let the engine bay get to dirty before cleaning it, but Purple Power does the job, and then I finish it off with a light coating of Meguiars Hyper Dressing to give a nice shiny look to the hoses and etc...

New Driver

thoughts on steam cleaning?


I don't have any personal experience, but from my understanding many swear by steam cleaning. I don't typically recommend it simply because it requires a decent investment to remove only some of the manual labor. If you are doing a lot of cleaning, it can certainly be worth it though. Much like the high pressure water jet, be careful with steam as it is still water that will work its way into electrical connections or other tight spots to cause corrosion. It is also hot enough to damage some brittle materials or remove decals if not done carefully.
Pit Crew

The cleaning issue I have is from a Coolant leak.  It's spayed rusty water all over my engine bay, and I can't seem to get rid of it.  I've tried Purple Power, brake cleaner, vinegar, nothing seems to make it budge on painted surfaces.  


Anyone have any ideas of what to use to get rid of this rusty stains?

New Driver

For rust stains, I use CLR. However, be sure to test on painted surfaces first.


OK guys, here's my lazy way to  get an engine spotless. First, run the engine up to WARM only. If you can put your hand on the headers it is just right. Then bag the carburetor and distributor with zip lock bags and zip ties. While the engine is WARM  spray a 50/50 mix of  Simple Green and water.  Let it sit for half an hour. Spray the mixture again. Then rinse the engine and compartment with hot water at garden hose pressure only. Repeat if necessary. Then I use the leaf blower to dry it all off. Be sure to get the spark plugs extra dry to avoid an issue. If the buildup isn't too heavy you shouldn't have to actually touch the engine. I've done this for 15+  years on my grocery getters and 2 show car/hot rods. If you can get under your car it does wonders for a powder coated chassis and parts. Simple Green is biodegradable and has a neutral Ph value so it won't harm electrical connections if you concentrate on the drying process.

New Driver

Have to agree with JHayden. Spraying with some oil like a wd 40 or engine based spray oil and wiping with rags is best option. Additionally, I've used the DIY sprayer at the carwash. However, only using the mist setting. And only when it was absolutely necessary to get off some road rash or something off the bottom. since my engine compartment isn't completely sealed off from the elements I've found that this misting helps with getting general dust off and some residue. Finishing by drying everything off in the bright sunshine repeatedly until there is NO visible moisture. 

New Driver

Thanks for sharing engine parts information in your blog

Grease Lightning and a small adjustable hose nozzle are what I use to control the water to where I want it.

Older cars you can get away with pressure washers and such but with newer cars you need to work more carefully and with precision.

I also tested and found products that will enhance different items in the engine compartment. There new spray on dressing for black surfaces will address many things from hoses to metal surfaces. It is not oily and will wipe to a nice shine.

Also clean at least once to twice a year and it will make it a much faster and easier project. Also please fix oil leaks and other issues that you may find as this will decrease the work.
New Driver

As someone who has owned many Crovairs in the past, pic 2 reveals the one thing that MUST be kept clean. Of course the cooling fins on the jugs must be kept clean,when GM hid the oil cooler UNDER the charging device(?) generator or later,the alternator,they did a real dis-service to the cars.
Hiding this cooler,plus the design of the pushrod tube seals that would not stand overheating,sent many a Corvair down the road with a "dirty duck" rear end. 4 carb head engines are rare these days. Take care of it, Mr. Smith! :0D