Broke Cylinder Head Bolt


While replacing head gasket I broke one of the cylinder head bolts. To remove I would have to do the entire job again. The engine is running properly. Can I get by without replacing it or is this not recommended.

Thanks guys!!!

Additional Info:
Mitsubishi Mirage 2000. Broken Bolt is the center front bolt.


Sorry that you didn’t take the head off immediately? Me too. You can run it until the head cracks. I don’t know when that will be. The leak may happen first. It might run for a long time from just good luck. The bolt may have been easy to get out but it was almost the last one you torqued. Good thing it’s on the end of the head and not in the center.

Not recommended. But if you’re lucky it might never be a problem (low odds of that though). I’ve seen stranger things happen.

You have to ask yourself a question…Do you feel Lucky?

I feel for you. It may hold…but it may not. The biggest problem might be a cracked head.

Did you use new bolts or the old ones?

You likely didn’t have the cylinder head milled, either, did you? The head is probably warped a little; which, often goes hand in hand with the head gasket going bad.
It’s not too late to take the cylinder head off, have it milled, remove the broken bolt…

I used the old bolts for the job. I had to remove the cylinder head to work on the valves. Their was no problem with the over heating or head gasket leaks.
Should I go ahead and repeat the work??? If I do should I have the cyliinder head milled? Should I use new bolts??? Also if I have to do this what do you guys recommend for removing the broken bolt which I think will be almost flush with the engine block.

Any chance of using an ezout to pull the broken part and put in a new bolt? Torque wrench and pattern? would one be advised to loosen the bolts and re torque propely?

Regrettably, it’s impossible to forecast longevity of a certain repair.
If you decide to remove the broken stud, I think it would be best to do it with the cylinder head off. Stud removal is a job, though it sounds simple, that can go very wrong. First, you want to center punch the stud to ensure that the drill bit goes through the center, not off-center. Use a reverse drill bit. It may, by itself, turn the stud out.
I suspect that the bolt could have bottomed on debris in the hole. The bolt, being used was already stretched. It may be stretched too long and hitting the bottom of the hole. Measure the bolt with micrometer, and measure the hole depth with a micrometer. Clean debris from all holes.

You have to take it back apart and remove the broken head bolt. The engine is going to only operate for a short period of time before the head gasket is going to fail because the head isn’t clamped to the block in that area. And if you’re lucky, there’ll be enough of the broken head bolt exposed above the deck of the block to get a Vice-Grip pliers on to remove it. Also, if the final torque of the head bolts specs out an angle of degrees instead of in FT-LB’s, these are torque-to-yield type head bolts, and cannot be reused but must be replaced.


Since I have to remove the cylinder head should I replace all bolts???
Thanks again guys you have been really helpfull!!!

Even if you get the bolt out and putting a new bolt in he could still have problems. Heads are suppose to be torqued down in a specific sequence starting inside and working your way out in a square/circular pattern.

Many manufacturers recommend/require to use NEW head bolts.

The reason it broken, is these are TTY (torque-to-yield) bolts. One time use. Anytime the spec calls for final torque at a degree turn, these are TTY bolts. If you pulled the head back off, to remove the broken bolt, replace all the bolts NOW.

TTY bolts are stretched to their yield point at final torque down, and will never again be able to recreate the correct clamping force if re-used. Once torqued down, they must be replaced if removed. Weak clamping or broken bolts will result if re-used. Especially with aluminum heads, new bolts are cheap insurance.