Stripped bolt on thermostat

[JimBee]

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.

[cn90]

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/

[JimBee]

I found a picture of the stud I removed with the two nut technique:

[xHeart]

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.

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.

The thermostat housing has upper and lower parts. Is the upper part threaded? I mean, does screw travels on the thread before reaching the lower part, as oppose to slide pass the upper part, and then catches, and continue threading on lower till tighten.

My concern is drilling a screw which pulls and fastens two surfaces could cause permanent damage to the housing itself.

If the upper part has no thread for screw to travel, then it is a lid, hence easy-out type of method has better chance of success.

The other hesitation is bit size with length that would clear the fuel rail. What size drill bit would come close?

[Ozark Lee]

The thermostat housing has upper and lower parts. Is the upper part threaded? I mean, does screw travels on the thread before reaching the lower part, as oppose to slide pass the upper part, and then catches, and continue threading on lower till tighten.

My concern is drilling a screw which pulls and fastens two surfaces could cause permanent damage to the housing itself.

If the upper part has no thread for screw to travel, then it is a lid, hence easy-out type of method has better chance of success.

The other hesitation is bit size with length that would clear the fuel rail. What size drill bit would come close?

The upper part of the housing is not threaded. You can drill away with no worries.

For drill size I use a drill that is slightly larger than the diameter of the bolt - I can't remember what size off the top of my head - and just pay real close attention to the fuel rail.

...Lee

[xHeart]

The other hesitation is bit size with length that would clear the fuel rail. What size drill bit would come close?

The upper part of the housing is not threaded. You can drill away with no worries.

For drill size I use a drill that is slightly larger than the diameter of the bolt - I can't remember what size off the top of my head - and just pay real close attention to the fuel rail.

...Lee

I picked up 2 housing screws, the thread would take 7mm nut = 0.275". My two bit choices are 9/32 = 0.281", 19/64 = 0.296". These two are close to 7.5mm. Do I need to go closer to 8mm?

I would place a stopper ring on the bit to take off the screw head's only, and not travel beyond 1 - 2mm after the head. Would 21/64 = 0.328" about 8.2mm diameter a better choice.

It brings me a step closer, thanks Ozark!

[xHeart]

There is also a choice of 1/4" left-hand drill bit.

[xHeart]

I found a picture of the stud I removed with the two nut technique:

The attachment T-stat stud w nuts.JPG is no longer available

I am thinking of using the two nuts method. The nut size is 7MM 1.0.
Would you delineate you procedure on more time. I am not sure it would thread from the top, would it?

shank still needs to come out

MVS_0237.jpg (401.78 KiB) Viewed 1644 times

Thanx!

[xHeart]

Out!

Read here...viewtopic.php?f=1&t=50844

[850TurboTurtle]

I cracked my housing using an impact driver to try to remove a stuck bolt on the thermo cover. So yes, use PB blaster and/or heat, and get better bolts before reassembly. I was in Portland when I cracked my housing, and the nice guys at IPD gave me a few new bolts for free. And told me some fun stories about tweaking a turbo 850 for speed... So, overall, not an entirely bad experience.