2.5 Exhaust Downpipe joint rusty bolts replaced

[Roberltd2]

Hi all,
I'm about to have to do this job myself (or my mechanic is anyway). What size replacement bolts to use? M10? And what length?
Is it ok to use stainless for this job? Are they more prone to fracturing?
Thanks in advance.
Robert.

 

[Rockhopper]

Mr Tyre did mine for £75.

 

[raymond.harper]

M10X40 part number 11621427586 according to realoem

 

[Roberltd2]

Thanks for the replies Rockhopper & raymond.harper.
This new layout doesn't seem to notify me of any replies.
Mechanic did the job. £120 cash. He did say that 40mm bolts were a bit too short so he couldn't use the spring washers on top of the plain ones.
Also that it was not the easiest of jobs to do.

 

[TIMMOS29]

The exhaust bolts on the downpipe joints had corroded away what was left of the two lower nuts were just about holding the joint together and of course the rust. The original bolts have blind splined heads that grip inside the upper joint holes and were seized in. Cut what was left of the lower end of the bolt so it was flush with the exhaust flange and gave the air hammer a go but it wouldn't shift the bolt. Ended up using a thin cutting disc in the angle grinder and cut a slot along lower and upper sides of the jointing brackets which took the tension off the splined end. A few rattles with the air hammer had them moving and out they popped. Replaced both with Stainless flanged bolts and flanged nuts put some Loctite on the threads, remains to be seen if it holds up to the heat but both nuts were fully tigtened and the joint tested leak free so the gaskets remained intact. I did fill the visible slot with exhaust paste to finish it off.
Upper bolts still have rusty nuts intact so these were left for another day, will be harder to get at these with an angle grinder may have to invest in a Dremel and give that a go.
Video by someone else doing this job but drilled them out,

I tried drilling but my new drills wouldn't touch the original bolts so resorted to the angle grinder and slot method.

Ive got get my exhaust manifold to weld it as its cracked but couldnt work out what the slot does ....sorry.

 

[colb]

The downpipe flange that connects to the rest of the exhaust has 4 studs in it to connect to the rest of the system. These studs and their nuts are usually corroded to such an extent that they are not fit to reuse let alone get them removed. The problem is getting the studs out of the flange they are held in by splines on the blind end of the stud and are extremely hard to remove even with the biggest hammer in your toolbox. The only sure way of getting them out is to cut or grind a slot in the flange down to the stud so that it releases the pressure on the splined end of the stud. Can be done on the car but you do need to take the exhaust sensors out as they do not like the shock from hammer blows and get destroyed from hammer shocks. Easier to cut the slots with the manifold off the car as its easier to access them. I replace the studs with M10 stainless bolts and flanged nuts. The pictures are of my old 2.5 but same principle for the 2.0l.
Pictures of rusty 2.5 flange studs
Stud and replacement stainless bolt
Flange with replacement bolt in place

 

[RMB]

Found this thread as I’m going through this pain currently.
Firstly I was shocked that bmw wanted £70 for the two gaskets and four nuts!
My mechanic managed to remove 3 of the nuts, the fourth broke.
So now I need a revisit and the stud knocked out and replaced with nut and bolt I guess.
Costing me a lot more than expected, but at least it will clear the only advisory off the mot.
He hasn’t refitted or replaced the flange steady bracket that I can see and it’s currently in a bag with the old nuts. Hmm

 

[colb]

Best of luck getting that broken stud out, only way to shift them is to cut a slot in the flange to release the pressure on the blind splined end of the stud and then drift it out. Be aware the exhaust sensors do not like shocks from hammering the studs out they die take them out before attacking the studs.

 

[RMB]

Thanks @colb i meant to ask if they should be removed. Great advice cheers

 

[RMB]

Oh I did see a video this morning. A guy used a blow torch just on the edge of the bracket getting it red hot then knocking it straight out with the air hammer, no cutting.

 

[colb]

He was lucky, I used Mapgas blowlamp on mine got them red hot and they wouldn't budge.