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Grace
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.

 

Read the full article on Hagerty.com: https://www.hagerty.com/media/maintenance-and-tech/3-dos-and-dont-for-cleaning-your-engine-compartme...

61 REPLIES 61
Brandan
Hagerty Employee

Great looking engine bay in the Corvair! Are those air cleaners anodized?

Kyle
Moderator

They are! They are K&N round filter smushed to ovals with thin anodized aluminum tops and bottoms. The factory air cleaner isn't so bad, but I like these better.
JHaydon
Intermediate Driver

Soften heavy, greasy gunk with your favorite penetrating oil (WD, JB, Kroil, Rost Off, whatevs) before you reach for the cleaner.  Cleaners typically pull out the oils, which just makes the gunk more solid.  Saturate it with spray oil (let it soak if needed) and wipe with paper towels. Repeat until it's clean.  Yes, it will probably take a couple of tries, but it will leave a shiny finish which will protect against corrosion.  You might even decide to skip the cleaner and leave it as-is.  

F360Spider
Detailer

I've been using a pressure cleaner with plain water for decades to clean engine compartments. It works very well, has no harmful chemicals and is efficient. The trick to using a pressure washer in the engine compartment is to know what components to stay away from and how close to a particular component one can get. The farther away, the less pressure. I don't recommend using this tool if you haven't done it before. Get a little carried away and you'll be replacing parts.

gec
Pit Crew

Little known fact: Liquid Wrench is one of the very best harmless solvents known to man. Softens & gets rid of old adhesive, grease & other pesky stuff. Better yet, it leaves no stains or residue; you can even use it safely on leather! Better than WD-40. A great product I've been using for years.
zachary
Pit Crew

Remember, Oil and grease are soluble in...well oil. A little fresh cheap oil will loosen grease and grime when using a scrub brush. Afterward you can rinse with water and a mild detergent such as Dawn. I also like WD-40. It helps clean and is safe on your hands.

Kyle
Moderator

Interesting point. I have used penetrating oil to break up stubborn deposits in the past, but never though of using some of the "bonus oil" that is often on my shelves. You know, the 1/4 quart left over after an oil change that never seems to end up being used to top off an engine...
golfnut53083
Intermediate Driver

For areas that are extremely "gunked up", I have had good luck covering the end of a flat screwdrive with a shop rag and loosening/removing the heavy stuff prior to applying a degreaser. 

TonyT
Instructor

Got a point-style distributor? Grab a plastic shower cap and a zip tie. Pull the cap down over the cap and wires as far  down as you can get it and snug it up with the zip tie before you get anything wet. And if you have any anodized parts like A/N hose ends or rocker covers, stay away from carburetor cleaner. It tends to strip the dye off of aluminum, leaving it streaky. I've had luck using 409 and an old toothbrush getting grime off of intake manifolds and cylinder heads. By the way, WD 40 is also an excellent solvent for cleaning slightly oily surfaces. Scrub the parts gently and wipe them dry. Allow the vapor to dissipate (about fifteen minutes) and go cruise.

56NomadJohn
Pit Crew

Be careful with WD 40, it’s highly flammable, only use small amounts.

Charlie
Intermediate Driver

I always used the H.D. engine cleaner, "Gunk", which I dilute with kerosene.  I spray or brush this on everything and let it rest for an hour or more.  After that, I rinse with the

garden hose without a high pressure nozzle.  Works like a charm.  Gunk is in all auto stores.  Or go to your nearest Harley dealer.

jsedelmann
Pit Crew

On vehicles from the 90s there is quite a bit of brittle plastic under the hood.  I would never use a power washer on a vehicle of this vintage.  I found that simple surface wipes work well.  Wondering what your thoughts are on plastic renewal products ... ArmorAll? Forever Black? Etc.  Cheers!

dough
Intermediate Driver

Having cleaned literally hundreds of engine bays over the years as a lifelong hobbyist and classic car business owner, it is amazing how few products and tools will get the job done.  A toothbrush, 3 or 4 cleaning cloths, 409 or your favorite degreaser, effort, and an eye for detail will go 85% of the way.  The rest will involve removing parts to refinish, or touching them up in place with the appropriate finish, paint, polish, or abrasive tool.  And I can't emphasize how much taking your time will help.  Doing one section of the engine compartment at a time (however you choose to break it down) can also extend your patience and, ultimately, your satisfaction.

Willall257
New Driver

Patience and a little 3XDawn,plenty rags like @ home improvement stores bagOpainters pretorn rags $5

DUB6
Technician

I've had literally hundreds of worn-out t-shirts over the years, and (cut up) they work fine as engine-bay rags.  I haven't bought a rag - other than for exterior cleaning - in years.  Firewalls and inner fenders are typically not as crucial as exterior finishes when it comes to cleaning, so t-shirt material suffices.

Watersmeet
Pit Crew

About every two years we just pull the mill out clean it completely, mask everything and paint it. After you've done it once or twice its a piece of cake. You know what wrenches to pull out of the box, where all the nuts and bolts are, what order to remove them, the best way to rig the hoist etc,etc. Does not take that long. Additionally if any maintenance is required its a lot easier on the engine stand than in the engine bay.

Its really not as difficult as it sounds and the engine bay looks great. Folks always comment on how nice and new it looks. 

Jim

DUB6
Technician

Extra work, but as I've lain on my back under a car and tried to work a rag or brush into tight areas with the engine in, I'm tempted to try this.  😀

RichardRuss
Passenger

 Ever since I completed my restoration of my e-type which included the engine compartment I have washed the engine down with GUNK. I normally wash the entire engine and surrounding areas at least once every other month while washing the car and the engine compartment stays spotless.

db2sub1
Pit Crew

 We owned a Mercedes AMG C63 awhile back and it developed an engine miss. The local Mercedes dealer checked it and recommended a new $14,000 engine bay wiring harness. The next farther Mercedes dealer said it needed $28,000 worth of repair. A friend told us about this old guy who's pretty sharp with cars. He diagnosed & had it running perfectly in twenty minutes; for $80. The problem? a friend who I let use the car had it detailed and water went into the spark plug wells, shorting out several coil packs. The old guy had a couple of used ones on hand and in no time everything was good again.

richreed701
Pit Crew

Two tips:  (1) It's easier to maintain a clean engine bay than to wait until it's Grunge City.  Of course, if you are resurrecting a barn find, or worse, a back-of-the-garage find, you need to do the heavy duty stuff.  But keeping a new car clean, even after 15 years, is way easier and needs less invasive chemicals and procedures.  Generally, I clean the engine bays every other car wash.  Good old Lemon Pledge works fine.    (2)  Motorcyclists have been using S100 for decades.  It not only works on all levels of dirt, but it leaves a nice finish on metal, rubber and plastic surfaces.  You DO have to rinse with a hose, so take the necessary precautions.  However, I have found that if your car can keep running fine after driving through a puddle, you don't have to go crazy.  FOLLOW THE DIRECTIONS!!!   S100 can be found at any bike shop, but be careful as they make you walk past all the motorcycles to get to the parts department.  

Kyle
Moderator

Great point on saying upkeep is significantly easier than trying to bring a mess back to glossy.
KickStart
Pit Crew

I’ve been riding motorcycles all my life and never heard of S100. I may try it. Thanks.

leigh
Passenger

After having spent the winter excavating my 62 Sunbeam engine bay and underside from layers of grime, I would second what dough says - there's no miracle product or replacement for good ol' elbow grease. I would add a shout out tho to citrus cleaner - Blaster makes a good one. Smells nice, a little less toxic and pretty effective at eating thru grease.   

KickStart
Pit Crew

Double post

KickStart
Pit Crew

For cleaning any metal assembly, I would certainly avoid citrus cleaners. They are water based and the citrus is an acid. It will get under bolts, screws, & nuts, or any other hidey place. I’m a retired toolmaker building injection molding dies and the PM shop use to use citrus cleaners, and after a tool sits awhile, they were finding rust. I suggested a move to WD-40 to clean with and the problem went away.
blue67
Passenger

Nothing will get all the way thru the thicker stuff without a good brush, that's the key to getting it to break down. I usually use Purple power or Simple green and a parts cleaning brush.

 

Mr_Wonderful
Navigator

I live in Maine, so I like to splatter extra oil on things. Great way to dispose of my 6 gallon oil change leftovers, great rust prevention. My frame gets a regular oil glaze as well. Filth and oily sludge isn't always a bad thing

DUB6
Technician

Yeah, that's why I loosen a few pan bolts on both the engine and tranny - let a little of that stuff leak out and cover the entire undercarriage.  Never understood why they make those darned gaskets so efficient at sealing.  Cheap undercoating, eh?  😆

69goatconv
Passenger

Simple Green and water 50/50 (with some scrubbing with a brush or rag) will usually take off any reasonable amount of grime. I use it 100% under the car as well. This is always followed up with spraying water from a garden hose over the compartment. Then blow off the remaining moisture with a leaf blower followed by drying rags.

Will
Intermediate Driver

You are correct!! Simple Green is the absolute BEST!! I have been a car nut for all my 63 years. I've been cleaning engine compartments for about 50 of those years. I have used lots of the products mentioned here, but Simple Green is by far the very best and it will not remove the writing from labels or cause discoloration. I will never go back to those other caustic degreasers. I spray it on all surfaces when the engine is cold, the use a 2" nylon paintbrush and a microfiber rag to detail everything. The paintbrush gets in all the little nooks and crannies. I rinse with the garden hose on the mist setting as I go, so the Simple Green doesn't dry on the surfaces. Then I dry it with a microfiber towel. I'll try the leaf blower next time, but the microfiber towel works well too.
loufig1
Passenger

The trick I use (taught to me about 30 years ago) is: once you have your engine compartment cleaned then every couple of weeks or more if you drive less, soak down the entire engine bay with straight Simple Green (BTW the engine needs to be stone cold), let stand for a few minutes (Brush stubborn stuff with a soft bristle brush) then rinse throughly with garden hose....  I have kept all my car's engine bays cleaned this way for many years...

jamespom
Passenger

I like Super Clean as it melts grease yet is biodegradable. 

Jaytemm
Navigator

 about steaming the engine clean?

Jay

Jaytemm
Navigator

What about steam cleaning???

Jaytemm

antijam
Pit Crew

I just clap my hands and the cleaning fairy works her magic.....

 

1-P1210831.jpg

TonyT
Instructor

Does she work cheap?

hhaleblian
Pit Crew

Anyone have experience with dry ice pressure cleaners. Very pricey, but appears to leave beautiful results. 

Kyle
Moderator

Vapor blasting? I wish I could justify buying one of those setups!
MST
New Driver

I also think dough has the most accurate assessment in my experience. That’s exactly what I did with mine and the before and after pictures are remarkable. Replaced as many rubber hoses as I could match, cleaned one part at a time, and removed and painted parts. Took apart things that I had no intention of removing but turned out necessary, and carried out some maintenance while I was at it. I open my hood proudly now.

jimliberty
Pit Crew

Easier to keep clean, than to clean. Once it is the way you want it, be sure there are no leaks, and wipe it off after every drive.      .....Jim.

LIBERTY MOTORSPORTS
DC
Intermediate Driver

“and most gearheads will debate polishes and paint protectants for hours on end”

 

seriously ?

Kyle
Moderator

Seriously. Anyone that uses polishes and other detail items seems to have a brand loyalty or process they swear by. Many cannot be swayed from their thinking.
DUB6
Technician

Oh I agree.  I've had guys argue throughout an entire 6-hour-long car show just about that subject.  Although what "rag" or "cloth" to use to apply or wipe off the detailing product can be almost as touchy a subject.  It's amazing to listen to the loyalty - and the bashing... 😄

yardsale88
New Driver

My buddy had his engine and underbody steam cleaned.  Both were pretty gunky, especially the undercarriage.  So far, so good as it has been a year.  Any other pros and cons of steam cleaning?

BobbyBaby
Passenger

A starting point on a recent cleanup of an old car engine area dirty, greasy, and gritty responded well to rags soaked in diesel fuel. I may actually be able to go directly to painting because the diesel dries clean.

RonZ
Passenger

The motor on my 1971 240 Z doesn't get greasy, but dusty at car shows.  So a garden hose washes off the dust, then my leaf blower quickly removes All the water.  My polished valve cover, chrome etc comes out perfect and quick.  Then wash the body.

Olexsy
Pit Crew

Using just the right amount of detergent and water especially under pressure can be delicate work. I use a small pressure sprayer communally used for lawn and pest sprays It can be found inexpensively at your local home improvement center. The wand reaches tight spaces and you have a precise control of the flow. Use your favorite degreaser, agitate thick stuff with a nylon dish brush from the dollar store and rinse off with the  sprayer. A small wet/dry shop vac will also help. First by vacuuming up all the loose detritus in the engine bay. Then after wet cleaning you can both suck up excess liquid that has settled and is not draining or reverse the hose to the outlet side and blow stuff out of tight places if you do not have compressed air available. 

Dano1953
New Driver

For the regular surface road dust in the engine bay, I’ve used Simple Green with great success.  Then either Trim Shine or Back To Black to restore shine to plastics and rubber.

2Sly4U
New Driver

I am a big fan of WD40. Spray a can on the entire engine compartment (no belts) and let it sit.  Then get some red garage rags and start wiping it clean, using a tooth brush or whatever is necessary for smaller, hard to reach areas.  Then I spray it again and keep it up until it's clean.  Sometimes I do it over time, letting it get cleaner each time.  I always spray the engine down lightly when finished to prevent rust and corrosion.  While the WD40 gathers a little dust, it retards the rust, so I just wipe it down occassionally and spray it again.  It makes ones engine look new over time, except for engines neglected for long periods.  BTW, I use this on my regular use vehicles too.  My engine bay always looks new.