Stripped bolt on thermostat

Post by **rmmagow** » 17 Jul 2012, 14:51

When reachable I've used my battery powered impact wrench for things like this. PB Blaster first, little tapping with a hammer, get a good seat out of the torx bit and whap it with the wrench. The battery powered impact wrench has become my favorite tool when it can reach.

Post by **JimBee** » 17 Jul 2012, 16:53

The hard thing on these screws is getting a good seat on the back one, though I've had to drill a front one off, too.
I' haven't used a battery powered impact driver, but I'm sure it can handle a bit so the tools I suggested above would work with it. That might be the ideal combination. Where''d you buy it?

chris91 · Post by **chris91** » 18 Jul 2012, 23:17

Shoot all I had to do was use a hammer and chizzel to get mine loose. I would say that drilling a small hole down into the center/top of the bolt and hammering an out tool into it so you can twitst it out and wouldn't have to much trouble with it. Or use a drill to drill a small notch in the side of the bolt head and use the chizzel on that spot. Make sure to try to hammer on the bolt to jar the threads loose.

Post by **xHeart** » 19 Jul 2012, 14:24

I am keeping it moist with PB Blaster. This weekend I will have a window of few hours to give the ideas a try.
I believe, 2 quarts of coolant would have to come out from the petcock drain first, right?

Post by **rmmagow** » 19 Jul 2012, 14:39

Battery Impact Wrench from Amazon:
https://www.amazon.com/gp/cart/view-upse ... 8PSHLK%2C1
$360.00 Very good tool for wheels, struts, etc etc. Better than electric (wired) nearly as good as an air powered of similar size.

Post by **patrioty3k** » 19 Jul 2012, 17:40

Hey folks,had the same problem about 2 years ago,my neighbor helped me out,great Corvette mechanic,arc welded a bolt to the bad screw,we replaced the thermostat no problem,actually kept the welded screw on,took about 10 mins,that back screw was no problem,replaced with a steel screw...

Post by **rspi** » 19 Jul 2012, 17:52

As you all know the screw heads are pretty soft. I drilled one off of my cam sensor with a socket driver and bit (ouch, took about 40 minutes but I was remote with no power or power tools). Taped the bit to a socket speed handle. Once out, it's easy to get a new one in there. Just don't tighten it so much.

Post by **xHeart** » 29 Jul 2012, 21:06

I have cleaned it thoroughly to assess if it would still have a chance to come out without intervention. Any feedback.

: thermostat screw...; MVS_0201.jpg (303.11 KiB) Viewed 1701 times

Post by **JimBee** » 29 Jul 2012, 21:52

This is the torx bit set I referred to from Harbor Freight.
http://www.harborfreight.com/8-piece-st ... 35187.html
The screw head you're working on won't hold the points on a bit now. It's too rounded out.

The socket drives the hex shank bits, you can use a 1/4" drive extension to get above the cylinder head. Then I used a 3/8" x 1/4" adaptor to get my 3/8" drive bar on it. I actually twisted one 1/4" extension before the screw turned, but eventually got that one out.

I have tried all the force tricks suggested above, including having a strong guy trying to turn the bit while I hit the side of the screw head at a sharp angle with a cold chisel. The chisel cut into the head and got a good purchase on it, but that didn't help the strong guy turn it. It still didn't budge.

Just drill it off. The torx well will help keep your bit centered. Use some oil on it. Get up over your drill so you can load some weight on it. Keep your drill bit nice and vertical—square on the head. That will give you a nice clean, square threaded stud to work with when the screw head is off.

If the stud is still frozen in the bottom half like mine was, take the other screw to the hardware store, get two nuts to fit it, carefully thread them onto the stud, then tighten them together. Before you thread the nuts on, slip a box wrench the size of the nuts onto the shank and let it rest there. Then thread the nuts on. Now lift the wrench to hold the lower one and tighten the upper one down onto it. Leave the wrench there til the stud comes out.

Then you will have a "new hex head" on that screw shank. Put some more PB Blaster on the shank where it goes into the lower half and let it sit for a while. Then use a socket on the two nuts locked together to turn it out.

DO NOT MESS UP THE THREADS near the top of the shank with a vice grip. If you try a vice grip, grab it low. You want the threads near the top clean so you can get the nuts on them. That's the easiest way to turn out the shank when you're that far.

Before you drill, work a paper towel or rag under the t-stat housing to keep filings out of your alternator, then carefully remove it when your done.

Post by **cn90** » 30 Jul 2012, 08:06

Some people remove the fuel line (but you don't have to) as this makes it easier.
If you decide to remove fuel line:
- make sure you have 2 wrenches: 1 for turning the NUT and 1 for counter-hold of the flared end (on fuel rail).
- cap the ends of fuel line (you can cut off a few "fingers" from latex glove and rubber band it).

See this DIY:
http://www.lakesidedp.com/volvo/Thermostat/

Stripped bolt on thermostat

Re: Stripped bolt on thermostat