I broke a bolt

[Bradd D]

I was replacing the battery hold down bracket on my 1990 325i vert and the bolt sheared off. What's the best way to remove the remainder of the bolt?

[bmwdirtracer]

Can you post a picture? It's been a while since I've worked on an E30, can't remember how accessible this bolt is.....

[dworthy]

+1

Depending if it broke off even or has a bit sticking out, you may have to drill it out. If some is sticking out, you could use a pair of vise-grips to remove the stub.

[ross1]

I'm guessing it broke off flush with the battery box. Corrosion from the battery acid has probably messed up the bolt sticking out below the battery box. You'll need to drill it out and re-tap. You might be able to somehow run it out the bottom avoiding the corrosion on the portion of the bolt protruding the bottom.
Crappy job, have fun. Use anti seize paste on the new bolt.

[Bradd D]

It's broken off flush with the battery tray. On a drawing I saw at RealOEM, it looks like there is some sort of nut or something on the bottom underneath the tray. Can someone post a pic of their clamp so I can make sure mine is actually the correct part or that the bottom of the battery is compatible with the clamp?

[stvsxm]

that nut is welded. look... that bolt is also relatively soft ... just drill it out to a tap drill size for 8mm 1.25 , ( start w/ a small drill on center as best you can first ) run a tap thru it the best you can and get a new bolt. you will end up cutting new threads but you should be fine. I can't imagine that you could get it out w/ an ez out or anything like above said , its going to seized solid... but you can try...

[bmwdirtracer]

I highly recommend using a left-hand drill bit ! All tool trucks have these (SnapOn, Mac, Matco). If you use said bit, with drill on reverse, the remaining bolt might just back itself out. It broke while you were installing it, after all....it is not seized, just overtorqued and probably rotted.

If this fails, I'd try a punch or chisel , in the reverse direction, to just back the bolt out. For this process....in example.....you hammer the punch into the remaining bolt at, say, 1 o'clock....and then try gently hammering the punch counterclockwise. If it moves at all, this is absolutely the path you need to follow.

[ross1]

It's broken off flush with the battery tray. On a drawing I saw at RealOEM, it looks like there is some sort of nut or something on the bottom underneath the tray. Can someone post a pic of their clamp so I can make sure mine is actually the correct part or that the bottom of the battery is compatible with the clamp?

Since the bolt broke off flush you have a better chance of running it the rest of the way through rather than trying to drag the crusty threads protruding from the other side back through the nut. Can you get to the back side of it? If you drill it with a conventional rh drill and it does loosen it'll just fall out the other side.