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Broken manifold bolt/stud

686 views 1 reply 2 participants last post by  towerymt 
#1 ·
Hi all,

Went in for an oil change today. Tech came over to me and showed me what was left of a manifold bolt. Apparently it broke from the head and it was wedged in between the heat shield. My question is what is the best way to fix this problem. I know how to take the manifold off to replace the gasket, but what if the bolt is snapped from the head. How do I get this out without damaging the head? Is there a special tool? Also, what size is the bolt and length as well as torque spec's. One last question. How long can I drive with only 7 bolts. Car runs fine and smooth. Will I damage anything. I just had the head gasket replaced 6 months ago.
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Regards Chris, '92 745 thats nearing 170K.
 
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#2 ·
Re: Broken manifold bolt/stud (cmd)

Drilling out a broken stud is done rather easily with the head off. With it on, it won't be so easy. I don't have much experience with removing broken studs, so I don't have any suggestions on what will work the best. Although I did have an exhaust manifold stud that loosened up and fell out, on my n/a B230F. I replaced it with the manifold on the car, although it's not screwed in quite as far into the head as it would normally be.

With a missing stud, you will probably blow out the gasket sooner, and it will make a ticking noise when that happens. I've heard it on my friends 240 turbo...it was obvious that it had an exhaust leak near the head or turbo. Stick something in the hole to measure how deep it is. You might be able to get a stud in most of the way, and at least put some pressure on that part of the exh. manifold so the gasket will last.

I'm going to estimate that the exh. manifold studs are about 35mm long. About 10mm sticks out past the manifold. About 20mm goes into the head. And about 5mm is not threaded, in the middle, but off center. I just had some of these studs in my hand within the past couple of weeks, so my estimation should be close enough that you can estimate how much of the stud is in the head. Or if you still have the broken piece...
 
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