bimmerZ

In the process of replacing the valve cover gasket on my 2008 550i with N62 motor. Removed the drivers side cover, replaced gasket and hand tightened each bolt. I have a crappy (i know) click-style torque wrench that I thought I had set to 7 ft lbs, which was actually 17 ft lbs. Ugh! The front left (standing in front) bolt snapped clean off. I drilled a hole in the center and proceeded to use a screw extractor to remove the broken bolt. Screw extractor sheered in half and now the hole I drilled in the broken bolt is filled with a piece of the broken extractor. I tried to re-drill the hole out, but that extractor will not drill apart!!!!

Any ideas?!? I am at a total loss here...

-Z

ripley

How far down the hole is the breakage?
What diameter is the bolt (small I'm guessing, 6mm)?

Since you can get a drill in there you could try a sequence of small holes (1mm ish) around the edge of the extractor to dislodge it. Need a steady hand to avoid breaking a delicate drill bit.

I would also resign myself to using a helicoil etc to repair the thread in the hole - that way you have more room to move getting the bolt out.

I always use the largest screw extractor that fits - I have broken small ones but never a big one.

Good luck.

twh

You will never be able to drill out the broken off extractor. Do what ripley says.

DavidF

Moral of the story is to stay aware from torque wrenches on the small non-critical fasteners. There is simply no reason to rely on a torque wrench for the valve cover bolts. Simply tighten until the nut/bolt bottoms out and is snug. The rubber grommet does the rest.

Hope the OP gets that broken stud/bolt out of the head without too much damage.

twh

I don't like the idea of not using the torque wrench when aluminum is involved. You need two wrenches - one for high range torque and one for low range torque. And, when you are near the bottom end of the range, test it out on some off-the-car fastener to see how it feels when it reaches the desired torque. My low torque wrench barely gives a click or feel on the low end and you really need to be careful. You can also buy a beam type wrench which you eyeball as you are tightening. Beam type are fine except you can't get your eyes on the scale in all positions you may need to use it. I do check the calibration of my click type wrenches using my beam wrench every year or so.

bimmerZ

Thanks to everyone for the replies! I plan to try ripley's method tonight. Assuming I get the small holes drilled around the extractor piece and can get that out, is the best bet just to continue drilling out the bolt and rely on a tap to retap the hole with clean threads? If so, any suggestions on how to fabricate a new bolt with the rubber grommet? I am wondering if this requires towing to the indy or if I should attempt on my own. I assume they would just do the same thing and charge me like crazy since i'm in a pinch. I live in Northern KY near Cincinnati, so my options are limited for local assistance.

twh

You should drill very small holes around the stuck bolt extractor as indicated. The idea is to drill only original bolt material and not bite into the base cylinder head. Maybe like 8 or 10 or more holes. After some holes, vacuum/blow out the pieces. If you can get a grip on the bolt extractor with a pliers, maybe you can get it out. If not, keep drilling around the drill extractor. Don't worry too much if you marginally wander into the original threads - your original bolt hole is probably toast anyway. Once you get the extractor out, get the left over pieces of original bolt out. Now inspect the original threads. Get a tap for the original hole. Clean up the hole with the tap. If the threads are mostly ok and you can torque the bolt to spec, I'd just proceed as is -- even some thread damage is probably ok as this hole isn't critical except to hold on the valve cover. If the hole is so damaged you can't even torque the bolt to spec, you'll need to helicoil the hole. You can pick that kit up at the local auto parts store. It involes drilling out the hole clean, tapping with a larger tap, inserting a coiled wire that is the original thread pitch. It isn't as bad as it sounds.

ripley

You already probably got this but its a good idea to cover anyplace metal can get into the engine while doing this. I usually use garbage bags and masking tape.