Oil spilling from engine oil filler cap - 300SDL - PeachParts Mercedes-Benz Forum

ah-kay · #1 02-10-2010, 12:26 PM

I am not sure whether it is the oil filler cap gasket or something more sinister to come. Oil is spilling from the cap after a short drive. The 300SDL has 331K miles and it always starts first time in the morning. I loosen the cap and do a simple blow by test and the cap hardly moves. However, if I remove the cap with the engine running, I can see oil droplets bouncing out of the hole. Probably driven out by the cam shaft. Is this normal?

I cleaned up the valve cover. The pictures show before and after 12 miles of driving. Shall I just replace the gasket or replace the cap? Or there is some blockage and the oil is not draining fast enough down into the crank case. Any info is appreciated.

okyoureabeast · #2 02-10-2010, 12:39 PM

I forget the acronym and the name of the hose that is on the left of the cap in the picture.

But in my 85 300D I was having the same issue. Oil was slowly collecting near the cap.

I ended up narrowing it down to the hose. It was poorly seated in the rubber connection hose and I think some of the blowby was leaking out because of it.

In my case doing that solved it. Maybe check the hose?

dadette123 · #3 02-10-2010, 01:20 PM

Looks like your breather hose is leaking. Part # 603 010 03 70 if it's an '87 SDL

bustedbenz · #4 02-10-2010, 02:04 PM

I've never seen that oil cap before. My 603 has a black plastic cap but the raised rib along which you can get a finger hold to twist it off is probably 2/3 the width of the cap, not just a little wedge. Can anybody confirm that the different caps (I've seen lots of mixing-and-matching going on with these things, in pics over the years) are perfectly fit matches? That he's showing a correct oil cap for this engine?

ah-kay · #5 02-10-2010, 02:11 PM

The cap came with the car. I have 2 more SDL project cars but I never cross check them to see whether they are all the same. It is possible that it is leaking from the breather hose. If it is leaking from the cap then oil would only spool around the cap but not as far as the left side of the breather hose.

My concern is that is it possible that the pressure ( blow by ) is too much underneath the valve cover?

Hatterasguy · #6 02-10-2010, 03:53 PM

Thats the original cap its probably shot, replace it.

The 603 has a cam lob that throws oil right their, if the cap doesn't seal it will make a mess.

Mercedes sells new ones for like $5, AFAIK they are all the same on every Mercedes built in the last 20 years so its an easy part to get.

The breather hose and gromet that seals it also get hard and leak, replace those to.

brakeengr · #7 02-10-2010, 03:59 PM

I had to double gasket the cap.
I bought a new cap from Phil, it didn't make any difference (oil coming out). Then got a cap from the dealer- remained clean for much longer, but after a few days, some traces of oil. I then just double gasketted it. Remains clean now....
BTW- my breather hose is also quite new.

TX76513 · #8 02-10-2010, 04:00 PM

Thats not the original 710 cap on that SDL. Replacments are cheap - fuel/oil same cap

Hatterasguy · #9 02-10-2010, 04:12 PM

Quote:

Originally Posted by TX76513

fuel/oil same cap

Not on the 603's.

dadette123 · #10 02-10-2010, 04:33 PM

you can get replacement gaskets for the original caps, I believe

Hit Man X · #11 02-10-2010, 11:54 PM

Quote:

Originally Posted by TX76513

Thats not the original 710 cap on that SDL. Replacments are cheap - fuel/oil same cap

What does the OE cap look like?

Also, like Hatterasguy said, the breather could easily be leaking. The grommet will fall apart if you attempt to remove the hose, be ready.

Chas H · #12 02-11-2010, 12:09 AM

The PCV (that's the acronym) valve grommet in the valve cover is leaking; and the oil fill cap is prolly leaking too.

bustedbenz · #13 02-11-2010, 12:58 AM

Quote:

Originally Posted by Hit Man X

What does the OE cap look like?

http://catalog.peachparts.com/ShopByVehicle.epc?q=&yearid=1986%40%401986&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6212%3AMBC|1512%3AED|10000100%40%40300SDL&keyword=oil+cap&subcatid=P:240392@@Oil+Filler+Cap&mode=PA

If that link works, it's to Phil's fastlane catalog with a picture. If it doesn't work, just pull up an 86 300SDL, search for oil cap.

The difference is the very wide "grab" bar instead of the tiny little one.

Hit Man X · #14 02-11-2010, 01:00 AM

Hmmm I thought the wider grip was an updated one.

bustedbenz · #15 02-11-2010, 01:01 AM

Quote:

Originally Posted by Hit Man X

Hmmm I thought the wider grip was an updated one.

I suppose it could be. I've seen it all, including the older style metal ones. They must all be fairly interchangeable. But all the SDLs i've seen on eBay/craigslist lately had the wide style, and I'm assuming that very few people would ever have seen the need to replace one.