Overtightened Bolt in Cylinder Head Cover

Earlier tonight I was tightening the five bolts on my cylinder head cover (also called a rocker arm/valve cover). Unfortunately, I overtightened one of the bolts and now the thread is ruined. What should I do? Is this beyond repair or can I live with it?

I have a 1998 Honda Civic DX. My engine is the D16Y7. It has four cylinders and it’s a single overhead camshaft. The engine is also aluminum, as is the cylinder head cover.

You should never tighten valve covers that tight…But the repair is fairly simple…Just move up to the next size bolt which might be 1/4" USS or 5/16. Buy a tap that size, cut new slightly larger threads and install a new bolt.

Like caddy man said, except stick with metric, like M6 or M7.

You could also get a thread insert kit. These tap larger threads in the head, but use an insert to replace the stripped threads so you can use the same bolt. That way, you don’t need to widen the hole in the valve cover, too.

Valve cover bolts only need light tension. Too much and you crush the gasket, spoiling the seal. Tightening too much guarantees more leaks. Especially with the rubber gaskets of that and many other newer cars.

Thanks for your help. I am enrolled in a car class (auto mechanics), so I will tell my teacher what you said and we’ll try to fix the problem.

When doing a valve cover gasket on cars like these, when you meet resistance from the bolt, STOP TIGHTENING IT!!! They have a special bolt with a short threaded section at the bottom and a smooth, dowel-like middle that is slightly larger than the threaded portion. This is meant to prevent over-tightening and crushing the gasket, or cracking the valve cover. You will need to get another bolt, available at the dealership and probably nowhere else, and a helicoil kit in the appropriate size to fix this properly. Hopefully the area around the bolt hole is wide enough to drill and install the insert. Next time around, use a torque wrench, or, if one is not available, a nut driver to tighten those bolts. They need very little torque to seal, and a nut driver, used with mild to moderate effort, will give you all the leverage you need to keep it from leaking, and prevent you from stripping the threads out of the head.