So for the past month or so i've been noticing an exhaust smell in the cabin while at idle. Obviously its an exhaust leak, but the question is where? I recently removed the downpipe without replacing the head-gasket. Could a new head-gasket be the fix and cause of the smell? I've also had the CEL light on for almost a month now due to pre cat o2 sensor. The car has 108k miles on it, so is it time for a new o2 sensor? or is the code related to the leak? thanks for any input!

 

It's most likely, the metal round gasket, where the DP, meets the male end of the exhaust (they get brittle). I have seen DP's warp where they marry the turbo or the studs stretch a bit. Also this triangle gasket is directional, make sure the concaved side facing in the proper direction.
Make the the O2 isn't loose, and check that the DP downs have cracks.
Good luck
Mario

mQubed Motorsport, Manic Tuning Dealer

 

dont get carbon monoxide poisoning while you drive

 

Since you touched DP recently, it would be logical to assume that you introduced a CO leak in so doing. Could be one of the gaskets on either side of the DP (mating with cat, or the exhaust manifold). Could be that the bolts connecting the DP are loose on either end. Could be that you did not tighten either one of the two O2 sensors.

I would start with checking all of the above.
CO poisoning is really hard to detect while it is in progress. BTDT on my college rust bucket. By the time you know, your reasoning and reaction times are already impaired. Not a good condition to have while you are behind the wheel. Fix this ASAP.

a

 

Safely jack the car up so that you can get under it without it falling. start the car and crawl under and listen for a farting noise coming from the exhaust. Pay attention to the joints, obviously, but also check the flex joints. You'll find it.

Don't forget to do this safely!

 

hey guys, i have the same problem but only at high speed or when i´m reving up above 3500 rpm/ under hard acceleration.
i get that weird smell like something burning, is this problem is cause by DP or exhaust gasket as well?
which gasket do i have to replace?
i have not touch anything on that area

 

^Try your exhaust gasket at the cylinder head and your turbo-to-downpipe gasket.

 

thank you for the advice, question: do you have by any chance the parts numbers of the gaskets?

 

What car?
How many miles?

a

 

Check out this site: www.realoem.com

Almost every BMW part is in this database. Search away.

 

afadeev, car is 2008 MCS r56

 

My money is on an oil leak.

Unless you've replaced your turbo cooling line and/or oil filter gaskets, both are due to be leaking just about now (assuming you are north of 50K miles).

Search the forum threads for pics and description of both failure modes.

a