I have two pipes with a rusted broken bolt stuck in the flange. It appears that the bolt is not threaded into the flange but just through bolted - can anyone familiar with BMW exhausts confirm?
I tried heating one with Mapp gas and trying to twist it with vice grips, but zero success with that method.
What does the hive recommend?
Thanks
If the piece is free of the car maybe put the whole thing in a can of rust remover?
Grind the broken end flat, center punch the bolt and drill it out.
Edit: Do that if bracing it properly (with a large socket around the nut end) and hitting it with a mini sledge to try and drive it out fails.
submerge the whole thing in vinegar for a couple of days. This will remove the rust which is currently acting as thread lock.
If you have a welder, weld a larger nut on the one that is there + vice + cheater bar.
The vinegar will do more for you than anything else.
Cutting it off and buying a new one? That looks pretty grody.
I'm sorry to say I can't remember whether that BMW flange uses a through bolt or a threaded stud, but I'm 99% sure it's a through bolt. I have taken the mufflers off E36s about fifty times and those are definitely through bolts. But I have done the mid-pipes on E21s, E30s, and E36s several times and I just can't seem to remember.
If it were me, my first choice would be to drill it out, but only if I could figure out how to get braced up somehow so I could get serious pressure on the drill.
There are exhaust flange repair kits on the market -- including BMW-specific ones but I don't think that would really be necessary if they are priced at a premium. I would use an angle grinder to split off the old flange. I would probably cut a piece of exhaust tube into a half-moon shell I could slide under the clamp so I didn't knick the pipe. The repair flanges are 2-piece units that bolt onto the tube, and they work just like a regular flange once installed.
Harbor Freight air hammer after the PB Blaster soak.
jfryjfry said:Grind the broken end flat, center punch the bolt and drill it out.
Edit: Do that if bracing it properly (with a large socket around the nut end) and hitting it with a mini sledge to try and drive it out fails.
Be my first approach. But I would also have it as hot as possible before the beating commences.
A couple cycles of heat and pb blaster followed with liberal use of impact gun is my standard operation for rusty or seized hardware.
To answer your question, that bolt should come off. It is not captive, at least on e30s, e36s and e46s.
I would second the idea of submerging in vinegar. It worked wonders on my Miata gas tank.
Vinegar soak or barkeeper's friend would work too. Like this:
Another option - grind the broken end flat, heat the flange as much as possible, punch out the broken bolt.
Find someone with an oxy-acetylene kit. MAPP doesn't get hot enough.
Get the flange cherry red, hold a candle on it (it will melt and wick into the gaps), let it cool down a few seconds to a dull glow, and buzz it with an pneumatic hammer or a drift and a BFH.
I can never get drills to work right. The mild steel or cast iron flange is always softer than the bolt and it walks into the softer stuff every time for me. Even in a vise on a drill press, the bit tends to bend/walk toward the soft stuff.
My E46 was a through bolt. Drilled, hacked and swore until there was enough new hole for a new fastener.
jfryjfry said:Grind the broken end flat, center punch the bolt and drill it out.
Edit: Do that if bracing it properly (with a large socket around the nut end) and hitting it with a mini sledge to try and drive it out fails.
This is exactly what I did on one of my BMW flanged, which looked identical to yours. cut it off, grind it flat, punch it, and drill it out.
Curtis said:Find someone with an oxy-acetylene kit. MAPP doesn't get hot enough.
Get the flange cherry red, hold a candle on it (it will melt and wick into the gaps), let it cool down a few seconds to a dull glow, and buzz it with an pneumatic hammer or a drift and a BFH.
I can never get drills to work right. The mild steel or cast iron flange is always softer than the bolt and it walks into the softer stuff every time for me. Even in a vise on a drill press, the bit tends to bend/walk toward the soft stuff.
gotta center punch it and start with a small bit, then work bigger. If you try to drill out starting with full-diameter bit, it will usually walk off-center.
Thanks everyone. Lots of good suggestions.
I'm with Curtis. Never had good luck drilling out bolts. Bits walk, or break off, etc. So, hoping to avoid the method.
I'm at the racetrack this weekend and brought the pipes along and some vinegar.
Just soaked one. Here it is after 16 hours. Definitely working the surface rust.
Looks like a job for a sawsall and a welder to me. LOL but then again, I'm set up in a way it would take me less time to do that, than try to drill it out.
One thing i've done numerous times on my own cars is just sawzall or cutoff wheel through the side of the flange into the bolt. Then, drive a wedge (punch/chisel) into the slot to open up hole around the bolt, then turn it out. Afterwards you can remove the wedge and use a through-bolt and nut, or if the hole will still hold it just clean threads and run a new bolt through it.
Curtis said:Find someone with an oxy-acetylene kit. MAPP doesn't get hot enough.
Get the flange cherry red, hold a candle on it (it will melt and wick into the gaps), let it cool down a few seconds to a dull glow, and buzz it with an pneumatic hammer or a drift and a BFH.
I can never get drills to work right. The mild steel or cast iron flange is always softer than the bolt and it walks into the softer stuff every time for me. Even in a vise on a drill press, the bit tends to bend/walk toward the soft stuff.
MAPP will get that flange orange if you wait long enough. BTDT.
I doubt a drill will even touch the bolt. It will be crystallized, which is part of why it broke in the first place. It will do a very nice job of making drill bits dull.
Better will to be to heat the BOLT. Heat the end still sort of sticking out until it's yellow (just short of melting), then take the heat away so you don't melt it, let it "cool off" (transfer heat to the rest of the bolt), apply heat again, etc. Ideally you can keep doing this until the heat soaks through to the other end of the bolt, making it red if not better. Heating ONLY the bolt will both expand it and make it softer, crushing it in the hole. When it cools off and shrinks down, it will be a looser fit. NOW you heat the flange and not the bolt, and try twisting the bolt out.
I wouldn't use a punch just yet, as if the bolt is well and truly seized up, all you will do is make it a tighter fit, like peening a rivet. Need to first make the bolt smaller, and then make the flange larger, with scientific application of heat.
Also. Drill it out a little bit larger so when it rusts again, it won't have the death-grip on the bolt that caused it to break in the first place.
I find it funny when people say things like "That whole flange is too rusty to use" or whatever. That is what those looked like after a couple years over here. Unseizing rusted fasteners is just part and parcel of working on cars, so we really know what works and what doesn't.
(What never works: Trying to take a throughbolt out that is still torqued. Always take the nut off first, then try to work the bolt)
....I should start a YouTube channel for this sort of thing.
I also should get moving - I have an RX-7 with eight wheels and tires and two Sparco seats and an ultra-rare Audi WK exhaust manifold that I need to deliver to... somewhere)
I found that old used brake fluid works well
Minor update.
One is out. The one I heated with Mapp gas and then pb blaster for a day. Air chisel popped it right out.
Second one is being much more stubborn. Soaked in vinegar. Multiple iterations of heat and pb blaster and air chisel and its not budged.
Have not yet cut the nut off. Probably cut and grind flush next. And maybe attempt to drill if air chisel still doesn't work.
Also found a company in Germany that sells 2 piece flanges, trying to confirm they fit. There are several companies on eBay offering flanges for e46 M3, But they don't list diameters to confirm fit on my z3m.
I had the same thing happen to me. I burned the bolt out
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