Emulsion on/near engine oil cap - PeachParts Mercedes-Benz Forum

supradupe · #1 01-18-2003, 01:04 AM

Hi All,
Would appreciate if anyone have observed this phenomenum. I sent my 98 ML to the dealer for an oil change (synthetic) this Tue. Today as I was checking the oil level and opened up the cap, I found some milky yellowish emulsion underneath the cap and the filler neck where engine oil goes in. First I didn't think of it, I cleaned it up and closed the cap. After about 2 hours when the engine cooled off, I reopen the cap and fould some water condensed unerneath the cap and around the neck. I checked the coolant level and there was no loss of coolant. Where does the water come from? This explains why I saw emulsion around the cap area. When I pull the dip tube stick to check oil level, the oil came out there was clean and transparent, no sign of emulsion.
Does any ML owner seen this before? I don't recall seeing this in my previous oil changes (all synthetic) and it does not appear on my other car either. What gives?

Thanks
steve

tabo · #2 01-18-2003, 01:17 AM

I never had that problem with my ML and I have 76,000 kms on it...

supradupe · #3 01-18-2003, 01:39 AM

I forgot to mention that the truck is running fine, I don't feel/hear anything unusual. Just looks odd to see emulsion at the unexpected place.

Gilly · #4 01-18-2003, 09:01 AM

Yes, at least in cold climates, they all do this (all 112 and 113 motors).
It's nice when the user profiles are filled out. I have no idea where tabo lives, but if he his somewhere in the sub-tropics, he wouldn't see this happen. Here in Wisconsin, it doesn't happen when the weather is warm.
It's just condensation. I believe the reason it happens is that the cap and the part the cap attaches to (the filler neck) are plastic and is cooler than the rest of the surrounding motor, which is metal. Never seen an official explaination, I believe this is correct though. Right after an extended drive it will be almost gone. Once the temps are above 30 to 40 F it will be gone also.

Gilly

tryan · #5 01-18-2003, 11:42 AM

steam rises. drive for a couple hours. the moisture will eventually go away

#6 01-18-2003, 01:23 PM

When I lived in downstate IL, that would happen every winter on all my cars prior to the M. Did not have the M in IL that long but I bet it would happen also. I don't think it happens in CO because it is so dry.

supradupe · #7 01-18-2003, 02:11 PM

Thanks all for the input. I figured it was condensation and I didn't drive the truck long enough to evaporate the water. But this brings up my next question. Why would water condense inside the filler neck? I presumed the engine compartment is a sealed system (when the oil cap is closed), isn't it?
My Nissan doesn't have this emulsion occur on the cap though.

steve

Gilly · #8 01-19-2003, 08:21 AM

BTW, we in the shop I work in refer to this as "motor snot".
It condenses there because the plastic cap and also (importantly) the filler neck are plastic and are cooler than the surrounding metal parts, such as the valve cover the filler neck attaches to.
I've never noticed this on the earlier engies, or any other current MB engines such as the 111 engine, where the plastic cap attaches directly to the valve cover.
I am unsure exactly how the moisture enters the engine to begin with, I would assume either slight amounts of normal blow-by past the rings.

Gilly