Engine Detailing Question - PeachParts Mercedes-Benz Forum

Bryan Harter · #1 08-09-2003, 10:07 AM

I thought I might do some engine cleaning after replacing the Aux Fans on my 1992 500E.

There seems to be a number of areas in the engine bay that have a brown/carmel/gold color layer of gunk that almost appears to be a sprayed on coating like an undercoat.
--- It appears to be a clear coat of some kind that turned carmel color.... Hard / brittle - requires physical scraping to remove.
It seems to be overspray on the airbox as well as engine / power steering reservoir.

First round of degreaser did not clean it up, I don't want to use anything too harsh on it. Any suggestions?

placo1 · #2 08-09-2003, 07:15 PM

Hi Bryan,

The coating that you're refering to is cosmoline, it was used back in the day to prevent corrosion on vehicles being shipped overseas. They usually sprayed the engine bay and undercarriage.

On plastic surfaces I would use full concentration Simple Green and be gentle. On metal surfaces either Simple Green or mineral spirits should do the job. Apply the mineral spirits on to a rag first and then rub the metal surfaces. Be careful not to apply it to any plastic, rubber or painted surfaces. Wipe the area with a second rag to remove any residue. Home Depot sells mineral spirits in various concentrations.

Note: On some surfaces I have not been successful removing the cosmoline and I've just replaced the parts.

Take some before/after pics.

Bryan Harter · #3 08-10-2003, 01:43 PM

Thanks Afshin -

Yesterday, I tried to use some mineral spirits and also GOOF OFF !
Neither seemed to work. I did clean up a couple of greasy spots using brake cleaner. The front edge of the center cover (in front of airbox) has a spot that is 2x2 inches. I used my finger nail to scrape alot of loose. It seemed to flake off.

The ABS brake box cover was a mess, I ended up scraping that with a knife and sanding it down / painting it.

Worst case, this might push me into having some carbon fiber covers made or buying new...

The top of the water pump is the worst looking part of the engine.
I will continue to research ways to remove the brown stuff before I tackle that.

I spent some time cleaning the engine bay on my CLK as well.
That just required some light soap and water...
Two things I noticed, lots of space under the hood (not something you see much these days) and the valve covers really have a very poor finish - almost a zinc link finish.
I have only lifted the hood once in two years....

If I could change anything on the CLK, it would be to add a bit more polish to the engine bay and the brake rotors...oh, also a small lip on the rear decklid.

KenP · #4 12-20-2003, 04:30 PM

I have this "brown" stuff all over my S500 engine... has anyone figured out how to remove it other than scraping it off? It is hard/brittle in most places.
Thanks, KenP

Johnson Chan · #5 12-21-2003, 05:14 AM

USE THIS INFORMATION AT YOUR OWN RISK!

When I changed the valve cover gasket on my car, it had the same problem you did. I used a SOS pad and razer blade and GENTLEY remove it. If you are not careful you can cause scratches. DO NOT use this method on plastic or rubber for obvious reasons.

And yes i tried brake cleaner, simple green, gunk, blah blah and none of it did anything. That cosmoline stuff is pretty resistant to chemicals.

placo1 · #6 12-21-2003, 01:10 PM

I just realized I hadn't updated my original post. After spending many mildly successful hours trying to remove the cosmoline with Simple Green Automotive Norm suggested I try a brass detailing brush.

A brass detailing brush can be used on the vast majority of METAL surfaces in your engine bay. Be careful because some of those surfaces are cad plated and the brass can and will rub it off. The brass completely removed the cosmoline from my engine block, stainless hoses, nuts/bolts and screws and clamps. After scrubbing with the detail brush use a rag and wipe of the residue. Start at the top and work your way down, the cosmoline creates a dust as you brush it off.

jbaj007 · #7 12-21-2003, 03:54 PM

Not so sure that the preservative is really true cosmoline (WWII vintage), but since we're calling it that, check this:

http://member.rivernet.com.au/btaylor/BMWText/technical/CosmolineRemoval.html

Tirebiter · #8 01-18-2004, 10:41 AM

Kerosine removes the brown goo (cosmoline).
BTW, goof off is merely high priced naptha. Use lighter fluid or buy bulk naptha.

toms · #9 01-18-2004, 07:15 PM

Just a question and a few thoughts. Why do you want to remove it? It is a protective coating. Might be less than attractive but original to the car. If you entered the car in a concours, you might get points deducted for not having the protective coating.

Also, current Star Magazine (Jan-Feb 2004) tells one how to restore the protective coating if it is inadvertently removed. This can be found on page 73..."If engine compartment is cleaned with solvents, protective wax (000 986 33 70)...must be reinstalled." This article suggests that it is important to retain the protective coating.

KenP · #10 01-19-2004, 05:08 PM

Well, on my S500, the "protective coating" has hardened and flaked off in pieces... on top of that, its badly discolored to a golden brown color... it looks like it was originally sprayed on the front of the engine, covering the water pump, thermostat housing, and about the front half of the valve covers. I'd say about 50% has flaked off on its own over the years. The remainder is very hard and totally resistant to any solvent I've tried.. incluiding lacquer thinner, kerosine, etc. Looks like crap. "Less than attractive" doesn't do it justice. :-)
I'd like to remove this remaining "stuff", clean the aluminum of its corrosion before the already apparent pitting gets worse, and recoat it with a fresh coating.
It might come off "inadvertently" on newer engines, but can't imagine that happening on mine... unless I was using dynamite under the hood for some reason...

mark cummins · #11 01-22-2004, 01:30 PM

Word of Caution...I Would Cover the Alternator with plastic when cleaning the Motor....Last time I cleaned the Block on my E320
I Got Some cleaning Liquid in the Alternator....It Took out the Bearings... Ahhhhh another lesson learned in Detailing