2.5 Exhaust Downpipe joint rusty bolts replaced

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Joined: Sat 05 May, 2012 22:46
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  Z3 roadster 1.8 TU
Location: Newport South Wales UK

2.5 Exhaust Downpipe joint rusty bolts replaced

Post by 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.

1999 BMW 1.8 Z3
2003 BMW 2.5 Z4
1998 Honda Deauville NT650V
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