I'm so glad you had your hands on my car to prove me wrong. Because, yeah, wiping that seal that's covered with oil anyway makes such a big difference. You do know that it's the clamping force of the cap against the seal, not the oiliness of the surface of the seal that does the sealing right? If you'd dealt with an engine that was pressurizing the crankcase even though the breather system was working perfectly, you might be willing to get down off your damn ivory tower. Oh well, can't teach an old dog new tricks.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Another way to look at it would be :

Some old dogs have long professional careers and learn from them along with much factory, dealer and aftermarket training .

You are correct in that you're unable to consider anything different, it's fine .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Be sure to modify your signature line "I'm not here to learn, but I say I am!"

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

What you're doing is called 'transference' ~ it's where you do a thing but are embarrassed so you try to blame others for what you do .

Regulars here all know I crave learning new things and am always asking, unlike you .

As I said, it's okay to be unsure .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

No, I'm conveying actual experience (including replacing the oil cap with no less than FOUR different versions [including 2 purchased directly from MB in Boerne]) and sharing that knowledge so that other people can learn from it. It's clear that your mind is beyond the ability to grasp new concepts.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Since we're down this path so far anyway, how about you tell the Ladies and Gentlemen reading this forum post why my oil cap kept leaking then? Since you know all there is to know with your experience and factory training, surely you have the answer.

Important key facts:

-Engine had high blow-by problems due to worn cylinders/rings and developed crankcase pressure at high RPM when hot, despite the crankcase breather being unobstructed and otherwise working properly.

-Original plastic oil cap had hardened gasket replaced with new OE gasket. Cleaned of all oil and installed. Still leaked.

-Original plastic oil cap replaced with Febi clone of original "short" style plastic cap. Still leaked. Replaced gasket and clean of all oil. Still leaked.

Thinking that the valve cover was deformed or damaged, verified that oil fill port was free of burrs, nicks, or other deformities. Fill port was square and clean.

-Purchased new oil cap from MB of Boerne. Was given the "short" style. Still leaked.

-Thinking old stock, took new oil cap back to MB of Boerne and requested the new style "tall" style cap. Still leaked. Cleaned oil, replaced gasket etc, still leaked.

Learned to live with it. High RPM would pressurize the crankcase enough to make a plume of smoke from the breather hole if the hose was detached and the engine revved hard. Obviously an extreme case of blow-by in a 603, but not unexpected for a high mileage diesel.

I'll await your response.

For what it's worth, the Febi cap is still on my 350SD and is leak-free.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

What I bought is Duralast Oil Filler Cap part number 8079.

https://m.autozone.com/external-engine/oil-filler-cap/duralast-oil-filler-cap-8079/4409_0_0?aqs=

__________________
Milan Brown 1979 240D, rebuilt OM617.952 turbo diesel, rebuilt 722.315 transmission (my only daily driver)

Instagram: @maximed93

How is the quality on this oil filler cap? My SL got a plastic cap to replace the leaking metal "OEL" cap when the heads were redone in 2002 and would be nice to have another metal one that isn't made of unicorn tears.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

On ebay I found a stainless steel cap manufactured in Turkey. I bought it and fitted an OE blue "rubber" gasket. Works fine and looks great. No leaks at around-town speeds.

It is true that at higher pressures caused by sustained high speeds there is still a little seepage. Just wipe it up and stop making an issue of it. Your engine is 30+ years old and has hundreds of thousands of miles. Most other engines would be boat anchors by now.

Just a somewhat related note on this topic - my oil cap (appears to be original factory) leaks a moderate amount. So when I was ordering some other parts from our gracious hosts/overlords here, I added a seal for the oil cap. The part they sent was completely the wrong size (outside diameter was correct, but inside diameter was about 1/4" too big). So beware ordering a replacement from here.

THANK YOU ! .

That looks like a Chinese copy, as long as it works O.K. the price is O.K..

When first I discovered the existence of the blue silicone cap gaskets I ordered a few and told my buddy at the M-B Classic Center about them, he said "the E.P.C. doesn't list that for any older M-B's" .

A while later it's the only one they ship .

-Nate

It is a Chinese copy of course, but fit and finish is good. Works perfect on my rebuilt OM617, my buddy has one on his 350k mile W116 300SD and it doesn't leak at all on his either.

For the price I am more than happy.

__________________
Milan Brown 1979 240D, rebuilt OM617.952 turbo diesel, rebuilt 722.315 transmission (my only daily driver)

Instagram: @maximed93

Okay, so I also have some seeping coming out of my oil cap on my 81 300D so I was planning on ordering a new one. I currently have the black plastic one and from what I'm reading in this thread, it seams as if the genuine metal MB cap might not be the way to go. Some of you seam to have had luck with the Duralast Oil Filler Cap (8079) which would be nice since it's cheap.

I guess my question is, which cap is the best to buy?

Oh, also there's some mention of a cap with a blue seal too?

laughable but this REALLY works!! had the classic black tears weeping out of the cap, even with a new Mercedes gasket. this photo is after hundreds of miles with no wiping cleanup.


the rope is just simple, cheap, weak, cotton rope. pure white to start with, it soaks up oil like crazy as you see from the uniform color throughout the rope.

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