2.5 Exhaust Downpipe Joint Bolts rusted away

[colb]

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.

View: https://www.youtube.com/watch?v=b8aKbU7rRf8

 

[Stevo7682]

Common issue to a lot of older BMW cars
Stephen.

 

[Lee]

I use the dremel method aswell, cut little slits through the flange into each stud, that way they just tap out and takes 20mins.

Saves what looks like could be a right headache.

 

[colb]

Yes Lee I spotted how you did it in one of your posts will try it with a Dremel on the upper bolts my angle grinder is too big to get at them.

 

[colb]

Over the last few days have returned to the exhaust joint rusted out studs after having replaced the first two. These next two have proved to be the most difficult fixings I have ever had to take out they are a real pain to get them to break free and access is really tight which prevents the use of a full size angle grinder cut off blade to put slots in the flanges, did try a Dremmel with small cutting discs but it wasn't man enough to cut the slots. Managed to get one out by using Map gas blowgun and then using the air hammer to drift it out. Onto the final one and that put up a real fight, ended up using a stone grinding stone on the splined end and ground the cap off it to reveal the outline of the studs splined shank, gave that a dousing with penitrating spray and some heat from the Map Gas, air hammer applied but it wouldn't shift. Popped out to Screwfix and picked up some metal cutting blades for my Recipricating Saw and managed to start a slot in the splined end of the exhaust flange just deep enough to start slotting the studs shank, applied some heat and then onto the air hammer, seccond blow with that and the stud moved out of its hole, its been fighting me for the last three days. Had to replace one of the gaskets which also needed some adjustment to the holes for the bolts as they didn't line up very well with the flange holes. Small adjustment to the gasket holes with a stone grinding tool sorted that. Stainless bolts and nuts fitted and all torqued down. Started the engine and thankfully no leaks. Just got to work out how I am going to get the seized rounded off duff post Cat sensor out now. At least if the Cat has to come out to get at it the exhaust joints will be easy to undo now.
For those of you with rusty exhaust joint bolts I would reccomend slotting the flanges to release the tension on those splined ends its less of a fight than drilling them out would be, if you insist on drilling use Cobolt drill bits the studs are extreamly hard to drill.