C350 (M272) - Exhaust fumes in cabin

[JamesG66]

I am suffering with exhaust fumes in the cabin of my W203 C350 (M272 - petrol).

The common view is that this is caused by oil leaking out of the camshaft core plugs and dripping on the exhaust. So at the weekend I replaced my core plugs but the problems persist. So I got under the car to look for any leaks in the exhaust and everything looks fine and there is no additional noise. I also checked my manifold bolts and they were good.

Following that, I did some more research and am now thinking it's crankcase breather related and I see that one of the two crankcase ventilation systems runs near the main cabin air intake at the back of the engine. I've never had something like this though so has anybody any experience of this happening? Could it be as simple as a split pipe?

 

[rorf]

You driving too close to the car in front of you

Probably a leaking exhaust manifold or the EGR pipe is broken.

 

[JamesG66]

You driving too close to the car in front of you

Probably a leaking exhaust manifold or the EGR pipe is broken.

Thanks, no EGR on an M272 of course.

A leaking exhaust manifold would make quite a bit of noise though, surely?

 

[JamesG66]

Update:

Took airbox off last night and investigated all breather pipes, which were all fine. While the engine was easily accessible I started it up and I can hear a hissing from the driver side so it seems to be manifold related afterall.

I'm hoping it's just the gasket and not a cracked manifold, but now beyond my skillset so off to an indy it goes.