Stripped bolt on thermostat

ovlov058R · Post by **ovlov058R** » 11 Dec 2010, 10:41

Hi
I also have an 1998 S70 N/A with 158 K miles.bought used W/143 K miles
The water temp is a little low on the guage on dash.
It is one notch lower than it should be, So I bought a thermostat for it , drained the water
loosened the back thermo bolt , (no problem) went to do the front bolt, is almost
stripped and is really torqued on there.(previous owners reefed that baby on there!)
I went out and bought an new torx bit, tried
to loosen the bolt with no luck
Has any one snapped one of these bolts off?
Has anyone tried using heat on the housing?
How much pressure can you put on these bolts ?
Thanks

Post by **thecheat** » 11 Dec 2010, 11:00

They sell easy-outs for bolt heads.. they look sort of like a socket with spiral grooves on the inside.

This is also a common problem with these bolts and they sell replacements at the dealer - or you can just go to the hardware store and match them with something similar.

You can grind the top of the bolt off and use vise-grips to remove the remaining stud. Not sure how heat would work here but I don't think it would hurt any. Just don't melt the thermostat housing.

ovlov058R · Post by **ovlov058R** » 11 Dec 2010, 11:46

Hi
I saw this problem earlier and bought the bolts for the housing ...
just could not loosen that one bolt
did not take a chance of breaking it
will that bolt take a lot of torque?
thanks

ed7 · Post by **ed7** » 11 Dec 2010, 12:29

Sounds like you haven't stripped it yet. Heat that bolt well, put the torx bit in the bolt and strike it firmly many times with a well aimed hammer. A little weasel piss on it wouldn't hurt either.
If you've got another pair of hands around, have the other put some effort on unscrewing as you hit the driver. Hand impacts are great in such cases.
It's the classic problem of dissimilar metals doing their thing over time. Heat ALWAYS helps.
Ed

Klausc · Post by **Klausc** » 11 Dec 2010, 12:53

The bolt will take a lot of torque, but you might want to try drilling a small dent on one side of the head. Then take a punch and hammer and tap the bolt at a 45 degree angle to get the bolt to move counter clockwise.

Just be careful, the housing is aluminum and cannot take abuse without cracking.

I put about 150lbs on top of the Torx driver (body weight minus legs) and tapped the driver with a hammer. Once the screw breaks loose it comes out easily.

Post by **Pauloil** » 11 Dec 2010, 13:48

yeah I push like hell on the T40 to be sure to get a good bite...

home depot sells nice replacements that I've used: M7 fine 30mm(7mm-1.0x30)

Post by **Ozark Lee** » 11 Dec 2010, 22:26

For anyone ever trying to replace a thermostat- FOR GOD'S SAKE - go and buy the new style bolts before you even try. There is about a 65% chance that the head will strip out on the old aluminum bolts and the replacements are around $1.00 each.

The choices after they strip out are an easy out or a drill to just cut the head off. Once the thermostat cap is off the remaining portion of the bolts seem to come off with ease.

The new style coated steel bolts are much better and they will not strip out when you go to replace the thermostat again.

...Lee

ovlov058R · Post by **ovlov058R** » 22 Dec 2010, 16:09

Hi everyone,
Sorry I did not respond earlier ,but I had to wait for better weather to do this, and if I had to order an thermo housing not to tie up the car.I moved the P/S pump out of the way so I could put some heet on the housing. I reefed on it a little bit more and POP! The bolt came out,changed the thermostat, replaced the bolts, put some antiseize compound on the bolts,put back together... Car warms up nomal, temp guage is at 3 o clock!
Thank you for all your help!

Post by **xHeart** » 13 Jul 2012, 12:06

...and BTW, I was to replace the thermostat during the new radiator install.

: snapped T40, while new thermostat in waiting; MVS_0144.jpg (319.84 KiB) Viewed 4201 times

Is there a better, and proven workable method for DIYers' to avoid this problem?

: hard spot to work...; MVS_0126.jpg (349.57 KiB) Viewed 4201 times

I am taking a break, since the current thermostat is working.
Is it T40 or T43, T45, T47?
What all must come out for a straight access while pulling out the stripped bolt?

Thanks!

byeboy · Post by **byeboy** » 13 Jul 2012, 18:51

Impact Driver with "real" hammer. they work well on bolts frozen into aluminum. Inexpensive, and a handy thing to keep in the back of the tool drawer.. Just slip a Torx socket on that 3/8" adapter!

When that doesn't work, a 1/4 cold chisel, striking the base of the bolt "sideways", so as to make it rotate. ...solved many a stubborn, stripped motorcycle bolt that way!