Fix stripped bolt hole in valve cover?

Well this is embarrassing.

I think I stripped one of the bolt holes in my valve cover. While tightening down one of the two bolts that hold down the right coil pack there was a loudish snap. It definitely sounded like stripping metal. This was very unexpected since the tool was just a small hand ratchet and very little force was being applied. However I just looked up the torque spec on those bolts and it's really low, only 6-8 lb-ft, so I must have exceeded that. Aargh. Not wanting to fix whatever it was immediately I didn't apply any more force to the bolt with the ratchet (in or out). The bolt was still holding tight enough that when I grabbed the top by hand and shook it it wouldn't move. The other bolt is in tight, so hopefully the stripped one will hold together for a while by friction on whatever is left in there.

I'm thinking that the bolt probably stripped the threads in the aluminum valve cover. Unless those bolts are brass instead of steel, in which case maybe it's the bolt that stripped. In any case, the next time I change that plug I'm going to have to deal with this. Or sooner, if it starts working loose. Or much sooner if that bolt hole goes all the way through the valve cover so that bits of stripped thread can fall inside.

Repair suggestions? Hopefully something less involved and expensive than replacing the valve cover.

Thanks.

Stripping a bolt does not produce a "snap" sound. All that happens is that suddenly the bolt no longer feels as though it is tightening (because it's not, as you've damaged the threads).
Maybe the pop sound was just something snapping into place?
In any case, it would be pretty easy to tap out a new thread in there.
I'm sure they are blind holes in the cover, so there's no chance of the bolt going right through.

i don't think it woud snap either. especially with a small rachet. i did mine pretty tight and nothing broke.

falsedawn said:

Stripping a bolt does not produce a "snap" sound. All that happens is that suddenly the bolt no longer feels as though it is tightening (because it's not, as you've damaged the threads).Maybe the pop sound was just something snapping into place?

Click to expand...

Like what? The coil pack was already all the way down to the top of the valve cover, and the top of the bolt was flush with the top of the flange on the coil that it goes through. I checked as best I could to see if the plastic flange on the coil pack had cracked and didn't see any evidence of damage. The car runs fine, so if something snapped inside the coil pack it wasn't anything crucial. Maybe it was so loud because it stripped on top of the valve cover and that acted like a drum to amplify the sound.

Hmm, or maybe the hole was stripped long ago and somebody "fixed" it with J-B Weld or the equivalent. Cracking epoxy might very well have made the noise I heard.

falsedawn said:

In any case, it would be pretty easy to tap out a new thread in there.
I'm sure they are blind holes in the cover, so there's no chance of the bolt going right through.

Click to expand...

This feels like one of those "it's easy to fix with the right tool" problems - but since I don't have any taps at all it's 100% certain that I will not have the right tool!

Just for the sake of argument let's assume that either the bolt stripped or the valve cover hole stripped. This may not be what happened in this case but certainly somebody, somewhere, is going to strip one of these someday. So what exactly needs to be done to fix it?

If it's a stripped bolt then unscrew it (or just pull it out if it's completely stripped), pick all the thread bits out of the hole (is there a special tool for this?) and put in a replacement bolt.

Unfortunately the bolts looked like steel and the valve cover is aluminum, so if something stripped odds are it's the hole. To fix that one would need a tap slightly bigger than the original (whatever size that was) and a bolt to fit the slightly larger threads from the new tap. And these would be obtained where?

If the hole's threads are stripped, your best bet might be to get a tube of liquid metal or whatever it's called, fill the hole with that, wait for it to set, then drill and tap a new hole.
If you do this, make sure you use the correct size bit for the tap and don't drill all the way through - measure the required depth of hole and mark it on the drill bit with tape.

Taps can be obtained at any hardware store - they are relatively inexpensive - see if you can get one that matches the thread on the other hole. You'll also need a tap handle - a set will come with one.

But really, these bolts are not exactly load-bearing, so I think you are worrying about a minor problem.

aluminum is VERY easy to strip out.....best thing to do is remove the bolt now and check the damage, as the bolt isnt providing any clamping force to hold the coilpack anyway....just retap and be more careful next time

Retap Larger or Helicoil (Search for It)