Short story......after changing the oil and adjusting the valves, I have spent the last day or so chasing down a decent oil leak on the valve cover. After cleaning it up, it turned out the oil cap gave it up. This was a Beck-Arnley replacement cap as the original had a broken tang on it. Anyway, it took three tries with replacement caps (including double gaskets) until I got one strong enough to seal properly. Does anybody know of a decent oil cap and gasket combo that will last more than 2 oil changes? Yeah I have used the fuel cap on it and it seals great, but can you use an old oil cap on the fuel filler, or does it need a vent to prevent vacuum buildup in the tank......just color me pissed off and frustrated right now.

Beck Arnley is usually junk. That said, you shouldn't be doubling up gaskets and everything else. How's your blow-by, especially at higher RPM?

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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!)

Wish I would have known Beck-Arnley is junk....guess I add them to Yep as brands to stay clear of. Blowby is moderate at high RPM. Not too bad or excessive, but it is an OM 617 with just shy of 350K on it. Cap doesn't dance at idle and only a bit at about 3000 rpm.

Uro not yep......damn autocorrect.

I've also had bad luck with Beck Arnley and also Gates
I bought my last oil cap from the dealership.
Think it was about $10 but it sure doesn't leak.

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1981 240D 4sp manual. Ivory White.

I may have to go the dealer route, but our nearest dealer is 2 hours away......on a good day. Anybody had good luck with a non dealer cap?

order it

Here's a question :

Do you carefully remove the blue silicone cap gasket and wipe it clean and dry each time you add / change engine oil ? .

I do and this simple thing stopped 90 + % of the oil weeps, seeps & leaks from the oil filler cap .

I use fuel filler caps as oil caps .

The blow by question is a red herring because the engine vapors are well vented to the intake .

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-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, it's not a red herring. It's an experience call. My SDL had high blow-by at higher RPM's due to worn cylinder walls. NOTHING would keep that oil cap from weeping (I tried 6 different ones, including two different dealership ones), the crankcase pressure was more than what that breather hole could handle at high RPM. Thankfully the 60x engines have a "moat" around the filler hole so it didn't make a big mess.

__________________
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!)

yes, it is .

My coupe's OM617 had a scored cylinder #5 and less than 200 # compression, once I learned to clean all the rubber seals it stopped weeping although the car billowed blue smoke every where it went .

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-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

I use a cap from AutoZone. For $6 you get a metal cap (not plastic) and I have no leaks from it (only some "seepage" because I place it face up with I remove it and don't wipe it off).

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

Instagram: @maximed93

I tried looking it up, this is what they suggested : https://www.autozone.com/searchresult?searchText=oil%20filler%20cap&vehicleSetFromSearch=false&keywords=oil%20filler%20cap

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-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

For crankcase pressurization causing leaks, it's entirely situational. Totally depends on the amount of blow-by volume which is related to only 2 factors; engine wear and power level... the latter not concerning *most* here on the forums.

I have a cap and breather that seals well under *normal* conditions but once the boost gets north of 30psi, the engine just breathes too much for the stock sized breather tube to maintain crankcase ventilation and it pressurizes out of the little weep hole on the side of the valve cover and from around the cap just a little bit. At 40lbs it actually breathes a little less... mostly because I can't keep head gaskets in tact so it comes out there first!

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{2010 Mazda 3 266,000mi} - daily since new, Airlift suspension + some chunky sway-bars: fastest pass 17.7@77MPH
{1987 300SDL 256,000mi} - stock turbo @ 22lbs straight piped + a whole bunch of pre-turbo water/meth injection, 722.3 with increased line pressure, special sauce, and shift kit: fastest pass 16.5@82
{1992 964 Carrera 4 Frankenstein ??,???mi} - 993 forward dated, Speedster conversion, GT45 + E85: fastest pass 12.5@113

I don't care what your coupe did with 1 scored cylinder. Try 6. Yes, the cap WILL leak with excessive crankcase pressure. The cam throws oil on the base of the cap, it only takes pressure a fraction above the ambient atmospheric pressure to push that oil under the seal. Plastic caps don't clamp as tight as the metal ones either, so they're more likely to leak with blowby.

Just because you're old and work on VW's doesn't make you an expert or a know-it-all on everything else. You always say you're here to "learn", you might try it sometime.

__________________
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!)

I learned, you're simply wrong and embarrassed to admit it .

__________________
-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