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Blowing/Farting Exhaust

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1,067
Hey all,

My M2 exhaust makes a blowing/farting sound when the car first starts up and it seems to get better but i can almost hear the sound bouncing off walls and stuff as i drive past with the window open.

Ive tested for leaks by shoving a towel in the end and running the car. Im getting air escaping from the cat end and the b pipe where it connects together. Ive done the bolts up stupidly tight to try and stop it but it doesnt help.

Do you think some gasket sealant will fix this or is the exhaust fubar? The gaskets are quite new as well...

Thanks
 
Pretty sure that joint's bolts should be at 25lb ft. How old is the gasket there?
 
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Pretty sure that joint's bolts should be at 23lb ft. How old is the gasket there?

Id say about 5 months old.... I think the bolts are pretty tight... i used a 400nm gun on them and then did a little extra with my hand wrench...

Post 1000!!! Just saying...
 
I would undo the bolts while you still can, replace the gasket, use some exhaust jointing compound and re-torque the nuts. Also inspect the joint when disassembled for any cracks or warps. Hopefully you won't require a new cat as they're not cheap
 
Cheers guys. The plan on Sunday (weather permitting) will be to take the whole exhaust off including the cat and inspect for cracks. The exhaust should be fine but the cat is the original and currently on 136K miles so it's getting on.

If all is well I will replace all gaskets and use some gasket sealant that is on order now and reassemble. Once left for a bit I will retest for any air escaping again. I will also check for rough edges and file those down. Wish me luck :).

Anything else anyone can think of?
 
Cheers guys. The plan on Sunday (weather permitting) will be to take the whole exhaust off including the cat and inspect for cracks. The exhaust should be fine but the cat is the original and currently on 136K miles so it's getting on.

If all is well I will replace all gaskets and use some gasket sealant that is on order now and reassemble. Once left for a bit I will retest for any air escaping again. I will also check for rough edges and file those down. Wish me luck :).

Anything else anyone can think of?
Someone sold you a knackered exhaust mate. No saving that.

Bolts don't need to be that tight. Take it apart, clean it up, refit old gasket with a smear of exhaust paste and jobs a good Un. Or stick it over the pit and we can have a look what's going on then. Sat or Sun evening when the kids are asleep would suit me.

Sent from my LG-H870DS using Tapatalk
 
Someone sold you a knackered exhaust mate. No saving that.

Bolts don't need to be that tight. Take it apart, clean it up, refit old gasket with a smear of exhaust paste and jobs a good Un. Or stick it over the pit and we can have a look what's going on then. Sat or Sun evening when the kids are asleep would suit me.

Sent from my LG-H870DS using Tapatalk

The exhaust is fine I'm sure ;). I'm away on Saturday day time but might be back in the evening. If not we could meet up on Sunday?

As you say, I'm sure things just need a refit and smear with gasket gunk :p
 
The exhaust is fine I'm sure ;). I'm away on Saturday day time but might be back in the evening. If not we could meet up on Sunday?

As you say, I'm sure things just need a refit and smear with gasket gunk :p
Yeah that's cool. Give me a text when you're back sat and we can sort it out.

I'll get you those pads as well.

Sent from my LG-H870DS using Tapatalk
 
Just to close this one off. At the weekend the leaks were resolved and the car now sounds 10x better than before with no farting!! Less vibrations in the cabin too.

Thanks for the pit usage Norv, it made the job much easier :)
 
Don't forget the cause! Cat flange was pretty heavily rusted and where it had swollen a bit the gasket had blown out. Chipped the rust off and sanded back. Rotated the gasket a third and used some exhaust repair putty and it's as good as new.

Still not quite as good as a facelift though...

Sent from my LG-H870DS using Tapatalk
 
Don't forget the cause! Cat flange was pretty heavily rusted and where it had swollen a bit the gasket had blown out. Chipped the rust off and sanded back. Rotated the gasket a third and used some exhaust repair putty and it's as good as new.

Still not quite as good as a facelift though...

Sent from my LG-H870DS using Tapatalk

Yea that too. Cheers mate. I prefer the headlights on the preface lift.... sorry :p
 
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