Mercedes ML350 W163 Oil Leak - Oil Filter Housing Cap

[Gillibrand]

My 2003 ML350 W163 developed an oil leak, which I tracked down to the join between the oil filter housing cap and the oil filter housing. I thought this was probably a duff O ring, so I replaced the oil filter and O rings, and the leak virtually stopped - but the operative word is 'virtually'. There is still a miniscule seepage after the car has run for a few miles. In my experience oil leaks don't get any better. I'm therefore now intending to buy a new oil filter housing cap, and for belt and braces I was planning to use a sealant (?silicon) between the plastic cap and the metal housing. I would really welcome any thoughts / experience on what has worked / what you think would be best. Thank you

 

[Wighty]

My 2003 ML350 W163 developed an oil leak, which I tracked down to the join between the oil filter housing cap and the oil filter housing. I thought this was probably a duff O ring, so I replaced the oil filter and O rings, and the leak virtually stopped - but the operative word is 'virtually'. There is still a miniscule seepage after the car has run for a few miles. In my experience oil leaks don't get any better. I'm therefore now intending to buy a new oil filter housing cap, and for belt and braces I was planning to use a sealant (?silicon) between the plastic cap and the metal housing. I would really welcome any thoughts / experience on what has worked / what you think would be best. Thank you

Thinking about my E320cdi om642 oil filter , when the o ring is replaced it would be easy to put it into the wrong groove near the top , mine is meant to be the second groove down (I believe)

 

[Gillibrand]

Thank you for the quick reply, but yes I did put the O ring in the right groove. I have changed the oil filter before and not had any problems, wondering if the cap has got slightly deformed. Engine has done 127K.

 

[Wighty]

Thank you for the quick reply, but yes I did put the O ring in the right groove. I have changed the oil filter before and not had any problems, wondering if the cap has got slightly deformed. Engine has done 127K.

I think a new cap for £20 ish might be a good start point first ?

 

[Gillibrand]

I think a new cap for £20 ish might be a good start point first ?

Yes, agreed. I was just thinking it might be good to add some extra sealant at the join. I know there isn't usually any sealer there, but want to make sure this is completely sealed.

 

[Wighty]

Yes, agreed. I was just thinking it might be good to add some extra sealant at the join. I know there isn't usually any sealer there, but want to make sure this is completely sealed.

I’m not sure about the sealant idea in case that then got into the engine next time you remove the cap ? What about a bit of silicone grease on the threads and o ring instead ?

 

[Blobcat]

I wouldn’t be putting silicone sealant on it.

 

[LostKiwi]

I wouldn’t be putting silicone sealant on it.

Me either.
The little bits that squeeze out have a nasty habit of finding their way into oil galleries.

 

[mattkh]

I oil the O ring.
Also, it is recommended to hand tight the cap.

 

[Gillibrand]

Thanks for the advice, and the fast responses. I have just ordered a new cap, and I'll try fitting that carefully; I won't try silicon, thanks for warnings re possible risks. I will report back as soon as new cap is fitted...

 

[Wighty]

Thanks for the advice, and the fast responses. I have just ordered a new cap, and I'll try fitting that carefully; I won't try silicon, thanks for warnings re possible risks. I will report back as soon as new cap is fitted...

The cap has the torque setting on the top of it , mine is 25nm

 

[Doug1234]

What brand of oil filter did you use ?.

I only ask this as I have a Jeep fitted with the om642 and on fuel filter changes certain filter brands have ill fitting o rings that often let the water sensor leak fuel out onto the top of filter... this may or not be the case with your oil filter but its possible that the large o ring is an incorrect size and oil pressure when engine running can overcome it.

For anyone interested if your water sensor o rings do leak on your fuel filter then I have found 16mm od by 2.5mm cross section standard o rings fit and fit nice and tight and save the need to buy another filter just to get some.