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Stripped Torx Head Bolt

by beefstu01, July 31, 2005

Well, this is just great.

So today I was under my '99 Prizm trying to swap out my AC compressor (it's different than the one in the Corolla), when I had two nasty surprises. The first was that the bolts were torx head bolts (stupid, stupid move GM), and the second, well, one of the torx heads was stripped. "Lucky" for me, it's on the bottom of the compressor, but still, only six or so inches away from the radiator.

I tried filing down two sides of the bolt (the head is perfectly round, the Torx star is recessed), but alas, six or so years of use, abuse and hideous Ithaca weather have taken their toll, and that bolt is pretty firmly in place. Granted, I did not file much off, but you get tired of that very easily.

The way I see it, I've got four options to take out this bolt:

1) Impact gun it. The T40 driver still grabs a little bit, so there isn't a perfectly round hole in the bolt, and there may be hope. Problem with this-- I don't have an air compressor, nor an impact gun, nor an impact driver, and I really don't feel like shelling out the cash unless I knew for certain that this would work. Also, I'd have to take out the radiator, which, while doable, won't be fun.

2) Screw extract it with an easy out. There'd be no way in hell that I'd be able to use an impact gun on it after I poke a hole in the bolt but, in theory, it should work. Plus, a screw extractor set is much cheaper than an impact driver. Problems with this-- I've never used one of these before, and I sure as hell don't want to learn on this bolt. Those things are brittle, and if it snaps, there's no way out. Plus, I'd have to drill a really straight hole in the bolt, and it's in a very awkward place, even with the radiator out. Also, this bolt is really long (5 inchish), pretty thin (6 mm, I believe, is what the threads into the block are), and quite torqued in.

3) File down the sides of the bolt more to make an impromptu hex head. At least I wouldn't ruin the bolt beyond all hope of recovery, and if I get it to a point where I can put a wrench around the bolt and twist, even just a little (I only needed about 1/8 of a turn), then the bolt will thread right out by hand. Also, I wouldn't need to take the radiator out, which is a nice plus to an otherwise sucky situation. Problems -- takes a lot of time, plus I doubt the bolt head was made to handle something like this.

4) Admit defeat and go to a mechanic around here so he can deal with it. I'll just get him to swap the three bolts for grade 10.9 metric hex heads, and love life afterwards. Unfortunately, he'll probably go for 3-4 hours of labor, charging me 150-200 in the process.

Do any of you know of any better way, or any good way to deal with this? I'm sure you can treat it as bolt head that just snapped off, but I've never had to deal with anything like this before, and I really don't want to mess anything up. It's also in such a hideous location! This day could not get much worse...

Any help would be greatly appreciated.

If the torx impact driver doesn't work (it may not from the sound of it) you may have to file the sides down to grab or just slot the head and use a flat blade impact.

You can get those electric impact driver or the the type that you can smack with a hammer.

Screw extractor work pretty well - but I have broken quite extractors a few on some really tough bolts. There are two types - the ones that look like "screws" that progressively taper to a larger diameter - just by screwing it in, tightens it hold of the screw. The other has stright flutes or has a square profile - those you hammer into the screw and turn to remove.

Sometimes an allen key will go into a bad torx enough to break it loose. Also try another torx socket- preferably a professional grade tool- it may hold enough to get it. Make sure the bottom of the recess is clean so you can get max grip. PBBlaster (a penetrant) may help.

total pita, just had that happen to me the other day after buying a brand new shop fan with a stripped out screw. I hammered a flathead screwdriver into the screw until it grabbed the bolt enough to turn it. made in china crap...

Well, I think I'm going for the last option-- admitting defeat and going to a mechanic. I was all gung-ho earlier today, putting the car up, filing down the sides of the bolt, pouring tons of WD40 around the penetrating part of the bolt, warming up the engine to hopefully make it easier to twist, etc...

Well, I got one (failed) try at it, and then the heavens opened up and dumped buckets upon buckets of rain on me. Of all days, today... it started out nice, it hasn't rained here for a month, and then it just opens up. It's just one of those days.

Feels as if something doesn't want me to get this damn bolt out, so I'll let someone else deal with it. Thanks for the responses, I guess I'm just cursed with hideous luck.

Ahh yes, we all have these stubborn bolt experiences. Not to fret, in some way shape or form, it will come out.

Try a good pair of vice grips. If you dont have a pair, go get one. They are a very useful tool in the future, but many people forget they even have them. Get those suckers on there just as tight as you possibly can and give 'er a try. Also, instead of running the engine to warm the area, use a torch -- again, a good investment if you dont have one already. Make sure you are warming the area around the bolt and not the bolt itself.

And instead of the WD-40 try PB Blaster which I have had pretty good luck with. (WD-40 is more of a lubricant than a "luquid wrench").

If worse comes to worse, and you still want to file the bolt off around the edges, try using a grinder. Only problem with that is it can make the bolt so hot it changes its hardness properties and thus when you try to get on it with a wrench it will just twist.

Good luck, let us know how it turns out.


Well, I got one (failed) try at it, and then the heavens opened up and dumped buckets upon buckets of rain on me. Of all days, today... it started out nice, it hasn't rained here for a month, and then it just opens up. It's just one of those days.

Feels as if something doesn't want me to get this damn bolt out, so I'll let someone else deal with it. Thanks for the responses, I guess I'm just cursed with hideous luck.

glad to know others have those days too. sounds exactly like me, the other day after I just got started mowing the yard and it came a flood. no more mowing that day. lol



WAHOO!!! I finally got it! After going through a can of liquid wrench, blow torching the housing, torquing it with a stud remover and wrenching on it with a pair of vice-grips, it finally came out, but not with any of that stuff. The trick (I remembered eventually), was to take the vice grips, and try tightening the bolt. This broke the crud off the threads and the bolt came out beautifully afterwards.

But the fun didn't end there! I put in the top bolt again when I had given up, and that torx head stripped as well. What I did, I think, ended up being pretty cool. First I removed all the other bolts on the compressor, and then started twisting the compressor, and for a ways, that actually worked. But alas, it got to a point where the bolt wouldn't spin any more, so at that point in time I busted out a hammer and chisel and started wailing on the bolt in desperation, and it finally came out.

I used a tap to clean out all the threads, then replaced all the torx bolts with grade 10.9 hex cap bolts with plenty of anti-seize and lock washers. I should have no problem with these bolts ever again.

So, for a stubborn bolt, try tightening the bolt first, then loosen. If that doesn't work, a chisel is very, very nice. Thanks for all of your suggestions.

Im suprised it didnt break on you from all the abuse prior to tightening it. I did that once and it snapped the head off, leaving only the threads...I was not pleased. lol

you should start a business, many people would pay lots of money to have someone extract bolts for them. I have been known to break off a lot of heads in my time (haha ... im only 22) and have drilled out many of them when the bolt extractors wouldnt work.

Ditto. Especially crappy brass screws around the house.

Vise grips seem to work for me most of the time. Failing that, f*** it; I drill in and retap the hole for a bigger screw or bolt!

For this (compressor) application, I can see the usefulness of a tight fit. The vibration tends to loosen fasteners.

Guest 98 Prizm owner with AC scr

I'm having the same AC torx stripped head problem. is anyone familiar with the length and thread of these 1.8 prizm Torx bolts? GM has them as GM part # 94858029 & 94858028 both discontinued!

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