Rear main seal leak?

[mRoadster06]

Hello all,

Noticed today that there is some oil on the bell housing on the right side of the engine. My first thought was rear main seal, but after some searching that doesn’t seem to be a very common issue on these cars. Is there another oil leak that’s more common in that vicinity (back of the engine, just above the bell housing)? And if so, what kind of damage am I looking at / any suggestions?

Thanks all!

 

[chris719]

Could be the constant pressure valve (CPV).

 

[mRoadster06]

Thanks! Is that a common issue on these cars? And located above the bell housing?

 

[chris719]

I'm not 100% sure on location since I haven't done it yet but I believe yes and yes. If you google S54 CPV you will find hundreds of results.

 

[mRoadster06]

Thank you!

 

[j3nks79]

The CPV in on the side of the block under the manifold. So nowhere near the gearbox.
If it’s the rear main oil seal the leak will come out of the bottom of the gearbox so shouldn’t be any oil on the top.
I’f you have oil on the top you need to check rocker cover gasket and see if it’s running down onto gearbox

 

[mRoadster06]

Very helpful, thanks!

 

[PDJ]

If it is the CPV you will need to make a tool up to remove it as a screwdriver bit will round it off

You need to get an socket that has an Allen key in it and cut grind it to a very good fit then you stand a good chance of getting it out with the engine in the car.

Then use a ratchet and wedge it it with a wooden leaver so it does not slip out and turn it out

When removed it needs a new O ring that's all

If you round it off there is no way of getting at it in the car

If the oil is coming out of the bell housing it can come from 3 places

Engine rear crank shaft seal

Brake fluid (an bit like oil)

Gear box input shaft seal

None of the 3 above will end well and will require the gear box out
I have done this on axel stands in a single garage so not too hard it is just all the other stuff that needs to come off to get to it.

 

[InterlagosMC]

Don’t know if it helps but I had a slow leak that I thought was coming from the front of my s54 and along the exhaust manifold to the back of the engine which I found no information about online, it turned out to be the rear exhaust cam position sensor o ring had failed, I had oil flow round the back of the engine and run down the side of the bell housing. Nice easy fix only took 10 mins and new seal was about £1 from the dealer. Remember to lubricate the seal before install if it is that.