I am going to use a combination of POR 15 Marine Clean (Amazing Degreaser) and high temp/high pressure water to clean form the block down and around my front suspension where my previously leaking oil line had been undercoating my car. Marine Clean is a great degreaser, I read somewhere that Simple Green has salts that will corrode certain finishes, in fact, this has happened to me, just make sure to rinse really well after applying SG . . good luck!

Folks,

I used to order "Easy Off Oven Cleaner" in case lots, used it to clean carbon from Pistons, skirts and crowns, it's great for getting carbon out of ring groves.....bear in mind that the pistons being cleaned were quite large, and weighed several tonnes each......the stuff is a great carbon solvent!!

I also used to order "Citri Kleen" in 55 gal Drums.....that is the best "all around" degreaser that I have ever found....."Citri Kleen" is an industrial cleaner that needs to be mixed with water for cleaning various surfaces, at farious strengths.

I try to use citrus based degreasers on my engines, am not an "organic" farmer, but I do my best to use products that don't harm the earth. (please note that I don't live in Califunya either)

SB

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Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

I think that typical oven cleaner is nothing but lye, which is a very strong caustic, which makes a pretty good paint remover, and is rough on aluminum, as already pointed out.
Working as engineer on tugboats I've spent many happy hours keeping the machinery clean, and have developed this approach for use on cars.
1) Get the engine compartment hot. Run the car pretty hard until everything is well heated up. Best to do on a warm sunny day. Heat softens grease, hardened oil, that sort of stuff.
2) Spray on Gunk on areas of built-up grease.
3) Use a brush to work over those areas down to metal, so that the gunk isn't just working on the top layer of hardened grease.
4) Spray the entire engine, undercarriage, etc, with some strong detergent. dishwashing soap ok, Simple Green ok, I like Citrasolv. Get it wet without washing the soap off.
5) Let it sit for 30 minutes. Detergents work over time.
6) Drive to the car wash. Use hot water and their most aggressive soap setting to blast off the engine. I do this with the engine running, so that the alternator spins any water right out of itself. Wear glasses. I also wear my foul-weather gear jacket and pants so that I don't worry about slithering around on the concrete.
7) Rinse with water.
8) I finish off by giving the machinery a shot from the "car wax" selector on the car wash. Does this help? Dunno. Can't hurt, is my theory.
9) Car washes have grease/oil traps in their drain system that will catch any oil slick. For that matter, so does the sewage treatment plant. That's part of what the car wash charges for, and why we (in my town, anyway) pay three times as much for sewage treatment as we do for the freshwater to begin with.
This is better than pressure washing off onto your lawn, or down a storm drain, where oil will go straight into whatever body of water your storm drains go into. In my case it's the Atlantic Ocean, which is right down at the end of the street.
NOTE. I'd be very careful using either brake cleaner or electrical parts cleaner. Many of these are perchlorethane (sp?), which is nasty stuff, I believe a proven carcinogen, and bad for your nerve system too? If you use it, don't breathe it, to the extent of wearing an organic vapor respirator, and wear good nitrile gloves. If it gets on your clothes, get the clothes off.
One "good old" degreaser from the good old days is carbon tetrachoride. I've never used it, but people say it's a good degreaser as well as a deadly poison.
seo

One step I would add to that list is to scrape the built up stuff off first before ever applying any kind of degreaser. This not only reduces the amount of grease that is getting washed off and running somewhere it shouldn't but it also allows you to use less degreaser because you don't have to melt a thick layer of build up before the degreaser actually gets to the metal under the grime.

Scrubbing all surfaces is the key to getting a really clean engine compartment. You will never get it spotless without significant elbow grease. I find the scrubbing therapeutic and I am more motivated to work on a clean Mercedes than one with diesel oil undercoating.

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Doug

1987 300TD x 3
2005 E320CDI

"Red Devil" drain cleaner mixed in a pump up sprayer is what I use to clean my tractor. Same stuff as oven cleaner, sodium hydroxide (lye).
Spray it on, let her soak, rinse very well, dry, follow with new coat of paint.
Do not use it on aluminum parts.

Oh yeah since this is the diesel forum, never spray a hot IP with water!!!!!!!!

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

You will corrode the aluminum and other parts. That is an alkaline base substance and will reek havock with the engine parts. Purple power is much less strong and it will eat the andonizing right off the parts. Dont ask me how I know.

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1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
Mercedes How-To and Repair Pictorials
I love the smell of diesel smoke in my hair

I've always had good luck with dish washing liquid mixed with hot water and spay on with a garden sprayer. Let it sit for a few hours and then give a second treatment. High pressure rinse and drip dry. Doesn't hurt anything but the grease and grime.

My favorite is WD-40 and a little elbow grease.

Safe on all your underhood surfaces. Just don't leave a bunch of residue behind or it will attract more dirt...not a problem if you clean at least monthly.

Down south in our shop, we use Wurth brake parts cleaner to clean all kinds of funk off our engines, it is really kind to paint also. It is not cheap, but it works for me.

I've used Gunk, Simple Green, CDC, kerosene, etc...... and none have worked nearly as well as a tip I found in a detailing book recently. Silicone spray works faster, and cleans better than anything I have tried in the past. If it is heavy, dirty, oily, caked-on crud, sure a more mechanical method can be used. But for everything else, including the painted fenderwells, I have never seen anything like it. Cheap too!

I started with cleaning the a/c hoses, wiring and assemblies on the drivers' fenderwell and let me tell you the results are exciting!

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Sam

84 300SD 350K+ miles ( Blue Belle )

Reading other threads here, I would consider not cleaning the engine compartment at all unless it was absolutely necessary. If water, especially under pressure, gets in the wrong place ambunch of problems start cropping up.

I hate silicone spray! Cheap car dealers always spray under the hood of there cars with it and man does it make a mess. Takes quite a while and lots of cleaner to remover.

There is not magic to having a clean engine, just a lot of elbow grease and some basic cleaners.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

It's a powerful solvent inside and outside the engine. And it doesn't generate toxic fumes and other harmful environmental byproducts.

I'm not talking about the silicone spray with the shiny coating that dries and locks the dirt in place. I'm talking about silicone spray lube. It does a great job of removing the grundgy film that degreasers and all of the other cleaners seem to leave behind. Believe me I was surprised at how well it worked.

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Sam

84 300SD 350K+ miles ( Blue Belle )