B7 Audi S4 - Rear Main Seal Leak??

[Manystylze]

Greetings Fellow Forum Members and Heroes of DIY !?!

I recently returned from a 3 week work trip to find a literal puddle of oil underneath my car. Prior to parking it in the garage, there was a small leak that surmounted to maybe a quart of oil between oil changes... After discovering this leak, my car was almost 3 quarts low.

This car is a daily driver so my assumption is that upon sitting for a while and being allowed to fully "depressurize", that whatever lord of vacuum seal was holding a gasket finally gave way.

Most of the oil seems to be coming from the rear passenger side. Photos (coming soon) will show leaks toward the front but I recently addressed those via a leaking oil filter housing and oil valley pan gasket.

Just wondering if my rear seal gave way or if there's some type of line I may be missing that's literally dumping oil...

**UPDATE***
Photos attached

20221201_111933.jpg Rear Belly Pan
20221201_112059.jpg Bottom view
20221201_112129.jpg Rear Subframe
20221201_112400.jpg
20221201_1124331.jpg

[CONative]

If it were rear main seal I would think the oil would be collecting at the bottom of bell housing. Oil cooler is on the passenger side but that’s towards the front and usually it’s just seepage from the bad seals. Can’t think of anything else though.


Sent from my iPhone using Audizine

[Rol-co]

At the back, solenoid seals, valve cover seal and half moon. If chains are done maybe the sealant between the covers but that is unlikely.

Other one: oil pressure switch can leak trough.

[Manystylze]

At the back, solenoid seals, valve cover seal and half moon. If chains are done maybe the sealant between the covers but that is unlikely.

Other one: oil pressure switch can leak trough.

I have replaced the oil pressure switch... twice, once by mistake in that I thought the first one went bad. I plan to pull out the borescope and look around the back of the engine tomorrow since I already have the manifold off and have some room to work/look around

[Dondbg]

Not the rear cover crank seal IMO, but it could be one of other sources.
As mentioned above, It could be one of the following:
Oil filter housing
Oil pressure switch
Chain solenoid seal
Half moon VC seals
VC gasket lower rear corner


I had a similar leak and ended being the pressure sensor…..

What I would is lift the car up, give it a good clean with degreaser and power washer and start the engine.

[Manystylze]

Not the rear cover crank seal IMO, but it could be one of other sources.
As mentioned above, It could be one of the following:
Oil filter housing
Oil pressure switch
Chain solenoid seal
Half moon VC seals
VC gasket lower rear corner


I had a similar leak and ended being the pressure sensor…..

What I would is lift the car up, give it a good clean with degreaser and power washer and start the engine.

Finally took some time to work through and noticed oil (again) on the passenger side. Seems to be the Oil Cooler housing. A bit under the weather but have pulled the front end and basically have it ready to put in service position prior to pulling the front clip to have more room to remove the starter and alternator if need be.

Saw a stream of oil and drip from the area close the the passenger engine mount and the cooler sits nearby. Going to try to get to it next week and take a few days to rest up.

[Rol-co]

Finally took some time to work through and noticed oil (again) on the passenger side. Seems to be the Oil Cooler housing. A bit under the weather but have pulled the front end and basically have it ready to put in service position prior to pulling the front clip to have more room to remove the starter and alternator if need be.

Saw a stream of oil and drip from the area close the the passenger engine mount and the cooler sits nearby. Going to try to get to it next week and take a few days to rest up.

thats not back but front of the engine, could be known oil filter housing leakage too, the belt shatter it all around there.

[Manystylze]

thats not back but front of the engine, could be known oil filter housing leakage too, the belt shatter it all around there.

Haven't pulled the front clip yet but have noticed passenger front side leakage since sitting. Just harder to tell when originally parked since it was blown everywhere underneath. Thinking Oil Cooler housing or hoses leading to it since it seems to be dripping from around that area around passenger motor mount

[Rol-co]

Haven't pulled the front clip yet but have noticed passenger front side leakage since sitting.

I put my money on oil filter housing everybody had/have, you can do the 2 checkvalves too.






It runs down the V to the front. No oil hoses at passenger side only water.

You need valley pan gasket, intake manifold gaskets, oil filter housing gaskets (2), valve cover gaskets i should do also when your in there.
If you put the front in service position you need the front motor mount also, its probably worn.

[Atomic Avant]

I put my money on oil filter housing everybody had/have, you can do the 2 checkvalves too.






It runs down the V to the front. No oil hoses at passenger side only water.

You need valley pan gasket, intake manifold gaskets, oil filter housing gaskets (2), valve cover gaskets i should do also when your in there.
If you put the front in service position you need the front motor mount also, its probably worn.

I agree with all of this, yours actually looks better then mine did.

Even if you don't put the car into its service position I would still replace the front mount. Mine was contaminated with oil and was easy to break apart by hand because of it.

[Rol-co]

I know

[Manystylze]

thats not back but front of the engine, could be known oil filter housing leakage too, the belt shatter it all around there.

Thanks; however during this process I have pretty much worked my way from top to bottom, now trying to do forward and rear. As such I have done the following:

1. Valley Pan gasket
2. x2 Oil sprayers
3. Oil check valve
4. Oil filter housing figure 8 gasket
5. Oil filter housing rear O-ring
6. Various vacuum hoses

Currently about to upload photos of the area around the Oil filter housing... with more questions, lol.

Thanks again for the feedback!!

[Manystylze]

I agree with all of this, yours actually looks better then mine did.

Even if you don't put the car into its service position I would still replace the front mount. Mine was contaminated with oil and was easy to break apart by hand because of it.

Haha, yeah I replaced that previously. Going to have to give the new one a bath in some cleaner though. I did the ECS Snub but it's seen some oil mascara recently

[Manystylze]

Here are the more recent photos after haven removed the alternator and oil cooler. It see, s there is oil ijn the upper portion under the exhaust manifold and around the starter. On the lower rear it is caked thick but not sure where it could be coming from.

Gonto clean all that I can see and track from there.

Oil cooler housing removal photo 2.jpg
Oil cooler housing removal photo 1.jpg
Oil cooler housing removal photo 6.jpg
Oil cooler housing removal photo 5.jpg
Oil cooler housing removal photo 4.jpg
Oil cooler housing removal photo 3.jpg

[Rol-co]

Gonto clean all that I can see and track from there.

Looks like a good idea!