The oil filler cap has a torque?????

Yep! it says it on the cap itself:
http://c1552172.r72.cf0.rackcdn.com/211186_x600.jpg
http://c1552172.r72.cf0.rackcdn.com/194357_x800.jpg

Just noticed this, were talking about the FILTER not the FILLER cap, sorry misread you. The filler cap does not

I must have misread your original post (filter not filler)

I can see the confusion there! I expect the new cap tomorrow. when I replace it along with another new o ring and if it still leaks, i'm wondering if my next step should be a new filter housing or try to diagnose oil pressure? fingers crossed for cap only! I know the housing gaskets go bad after a while, but has there been any issues with the housing itself deforming/cracking? seems unlikely..

The bulging and 'sucking in' of the O ring should not happen. I think the cap and O ring will fix your problem as long as the issue with the O ring is not due to over tightening the cap. Once the O ring is deformed it is not going to seal properly.

You do realize the 25NM is 18ft/lbs?

yeah, though again its never been an issue :dunno: i'm confident in assuming most folks don't use a tq. wrench on the cap, but maybe i'm way off base on that? hand tight and and a quarter turn with the tool historically has got it done. im going to use a tq. wrench this time just so I know its not over or under torqued! if the trifecta of new o ring, new cap and correct tq. spec doesn't do it ill have to explore my options.

I service a fleet of 25 Mercedes MBE900s - all with plastic fuel, oil & certrifuge filter caps - all with 100,000 miles +/- and have never used a torque wrench. The only time they will leak is if the seal is damaged or I wait too long to change the filter(s). (Knock on wood)

:iagree: I don't use a torque wrench either. I always check for leaks when I first start it up after oil and filter change and also the next day. I would rather check it to see if I didn't get it tight enough than get it too tight--if it leaks from being over tightened I will more than likely need a new O ring and have a mess on my hands doing the swap.

I use a torque wrench just because it's simple enough to do, but prior to that I always used hand tight plus a quarter to a half turn at most. No issues for me on any cars.



The oil pan drain plug? That I definitely always use a torque wrench on!