Broken Head Bolt

[crash2458]

So I had a timing belt failure on my 04 Aveo. Took the head off and had it looked over by the machine shop. Miraculously there were no bent valves so they ground a couple valves that weren't sealing and milled it. So the installation was going fine until I was torque angling a head bolt for the second round. The bolt broke off down in the block. It was the bolt in what I will call position number 4 which would be the fourth bolt to be torqued according to all of the diagrams I have seen. So what are my options now? Do I finish assembling and hope for the best or do I tear it all down and try to remove what is stuck. Do you think it will hold for a little while or will it be an instant failure. I don't even know why it snapped. It did seem oddly more stubborn than the other bolts. Not quite sure that I even know how to try and remove what is broke off if I did tear it back down. Thanks..

[avguy]

I don't think there's any chance for long-term success with a head bolt missing. IMO, you should pull the head back off, get a new set of bolts and reinstall. It sounds like maybe there was coolant in that block hole, which would leave no place for the bolt to go. The other possibility would be cross-threading, but that's not nearly as likely. If it's not cross-threaded, you can drill with left-hand drill bits, and use a large shank screw extractor to remove the broken bolt. DO NOT try to force the extractor if it's not turning easily. Have it towed to a pro who does this stuff every day. And who knows, maybe you will even get lucky on this one and have enough bolt sticking out to grab onto and just turn it out.

[camopaint0707]

do it the right way and don't risk losing the engine cause you were too lazy to remove the bolt you broke

[crash2458]

SUCCESS!!! Drilled through the bolt and extracted what was left of the bolt. My only concern is that I drilled through the bottom of the bolt about and eighth of an inch into the block. It doesn't appear that the threads were damaged except for maybe a minuscule bit at the very end. Guess I wasn't as straight as I thought I was! Still wish I knew why it broke.. Any thoughts from the garage? Thanks.

[avguy]

Good to see it came out without any problems. So there was no coolant or debris in the hole? Did you try running a new bolt down the hole to make sure it turns in easily all the way, and also to check that it can go down as far as the others do?
The FSM for some vehicles says to always discard the old head bolts and use new ones. I don't have the actual FSM for the AVEO, and wonder what (if anything) it says about that.

[Mike Sal]

Glad you were able to drill thru the bolt. Probably no long term damage to the the drilling operation.

The kit I bought for timing belt repair came with a set of new head bolts. Apparantly they use crap metal to make the bolts.

Why do they use this goofy 60, 60, 10 method of torqueing the bolts.....seems dumb to me. Why can't they just give us the specs for each round to tightening so you know what you've got (not everyone can judge 60 degrees....)?
Mike Sal

[06T200]

Two guesses: A devious plan to sell us more tools, or to enable the use of cheesy fasteners? I know many DIY'ers that re use these non reusable bolts and they seem to do ok. I guess it depends on the quality of the fastener. For $31 bucks I will avoid the risk since I don't plan to ever be back in the engine for a while.