Some total moron prior owner used some non-standard bolts on the exhaust donut flange clamps on my '89 535i, and the bolts are totally fused with the metal of the flange. No amount of cherry-red heating with a torch, or attempts to break the bolts loose with a breaker bar, thermal shocks by cold water after red-hot heating, or penetrating oil helps. The metal shanks of the bolts have fused with the metal of the two flanges, i.e., completely filled and sealed the bolt holes.
I've cut the bolts between the flanges to separate the fore and aft sections of the exhaust pipe/cat/muffler assembly, but cannot get the bolts out of the flanges. I may have to simply cut off the flanges, then find an aftermarket replacement such as this:
https://www.amazon.com/Nickson-Indus...n+split+flange
Will this or otherwise what aftermarket flange clamps will work with our flared exhaust pipes/donut rings? What size fits best?
Last edited by Dash01; 06-16-2018 at 09:43 PM.
Why not just burn out the old bolts? Seems like you have torches
If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue
Not sure if this might help... Maybe you can drill out the old bolts and then restore the thread with a tap? It happened to me with an oxygen sensor (had to get an "oxygen sensor thread restorer" -basically a huge tap, but same idea).
I used 2 of these for my 89 535i when I had to cut the down pipes. These things are absolute beast clamps, it's the same design idea as a generic band clamp but they are significantly stronger - they will support the weight of the exhaust system, where a band clamp typically will not. They also seal very well.
https://www.fcpeuro.com/products/aud...amp-191253141f
They are OEM clamps for various manufactures/models, and come in various sizes. You have to do a bit of digging to find the size you need, and the prices are all over the place. The one I linked to above fits the down pipes, but I am not sure if that measurement is the same for the rest of the system.
85 325e m60b44 6 speed / 89 535i/5
e30 restoration and V8 swap
The finished product!
To answer my own question about Nickson aftermarket exhaust clamps, yes they do fit in 1.75" to 2.0" size, about $5 each at Autozone. The factory clamps are made of some seriously hard steel, but can be cut off with a Dremel reinforced ceramic disk, or a cutoff saw.
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