Well I spent the biggest part of the day yesterday changing my thermostat and running from place to place to get parts. I had the thermostat but not the Coolant Temp Sensor. First I called one of the local dealers to see if they had one and they had the sensor in stock and was open until noon.

So I sprayed the bolts down good with PB Blaster for 2nd or 3rd time and then decided to take the torx bolts out before going to get the sensor. I stripped the front one slightly but somehow managed to get it out. The back one just rounded out immediately.

WHY THE HELL DO THEY USE THE STUPID TORX BOLTS!!!

I honestly don't think there was anyway to loosen that thing without stripping it. I had the fuel lines out of the way too so I could get straight down into it and I have a very good set of torx bits. The heads may have been stripped slightly from somebody previously changing the thermostat though. I don't know for sure. I know I never had them out before because I never put them back in.

So then when I go to get the sensor I also go and buy a dremel tool to cut the bolt. No way could I get that down to the bolt to make a cut. So I take the old electric drill and try and drill down through the head of the bolt. Ruined two bits trying to do this.

Oh yeah on the dremel tool. When my wife saw it she said that's just like the one I got for doing the dog and cats toenails. So I take the dremel tool I bought back and get a very strong metal bit. I drilled that head off in about two minutes with that bit and the housing came right off.

Once I got the head off the stupid torx bolt I drove up to the local NAPA and bought steel tempered hex bolts. Probably could have been done in less than a 1/2 hour if they used regular bolts. Instead I started about 10:00 am and finished about 4:00 pm.

Temp gauge is now sitting right at 3:00 so I did need a new one.

 

yes it's a common occurance. I did the same thing to mine, and left it that way for a while after getting discouraged after stripping the second bolt.
It did help my MPG alot.

Apparently volvo used aluminum bolts, which is why they always strip, but if you were to go buy them new there now made of steel.
So that's what i did, i know i had to drill mine off too!

I hope you put alot of anti seize when re installing!

 

I just changed my thermostats on both my Volvo's yesterday. I found that using the torx socket and extension did not allow the bit to seat all the wall in the bolt head. The extension would hit against the valve cover. I went and purchased a wobble extension which allowed it to fully seat. Another trick i learned from a Porsche mechanic was to insert the torx socket and take a hammer and lightly tap on the top of the extension while the bit is inserted into the bolt head. This fully inserts the bit and hopefully starts to loosen the bolt. My bolts came out fine but alot of force was required. I used anti-seize on all upon reassembly.

 

I've never had the problem with the thermostat but did with the CPS. When I did the cam seals on the exhaust side, I thought, man these torque bolts strip easy. Since I didn't have replacement bolts I put them back in and thought, I hope I'm not the one that has to take that cam sensor bolt off when the time comes. Well, 11 months later it went out and there I was, with a hand drill (home made) trying to drill that bolt out so I cauld finish a 15 minute job. Took me 30 to 45 minutes to get the bolt out with my home made drill.

As for the coolant temp sensor, I have never replaced one of those.

And the drummel... My wife had a tool kit for her finger nails or something like that that had a tool in that I use to use.

 

The rule of life is to buy new bolts before you even start to try to change out a thermostat with the old style aluminum bolts. There is a 99% chance that the heads will strip out on the aluminum bolts.

The Porsche trick of "waking up the bolts" has worked for me but you must wake them up like you are waking up your wife - very gently. The thermostat housing is fragile and to big of a tap, or whack, will break the thermostat housing.

On one of my cars, I can't remember which one, I drilled the head of the torx bolt off with either a 1/4" of 5/16" drill bit and then used vice grips to remove the remainder of the old bolt. Once the head of the bolt is off, and the thermostat cover is off the remainder comes out easily.

On the back bolt you need to be careful around the fuel return line so as to not nick it with the drill bit.

I did coat the threads on my new coated steel bolts with anti-seize compound much like a spark plug when I put them back in.

...Lee

 

I was tapping them kind of heavily with an impact wrench and still could not get them. I then hammered an oversize torx bit into them and that is how I got the front one. The back one would not budge. Once the head was off and the casing removed the remainder of the bolt came out with my fingers. For some reason I alway replace the engine coolant sensor when I do the thermostat, not sure I need to, but I do anyway.

 

Maybe my bolts were already replaced with steel ones. IDK

 

Are you guys sure? I've never seen aluminum bolts on any cars I've worked on; that's just nuts!

 

Sounds like we are all doing similar repairs.

Bought a thermostat over the weekend, havent gone in yet. Looks like: wobble drive, Parts Breaker, gently tap the torx drive to seat it. Wonder if an impact wrench (with the high speed vibration) might help, maybe some heat too. Replace with steel hex bolts and antiseize, torque down to spec. Sound like a plan?

Trying to get that temp needle up to 3:00... Dave

 

my needs is just a hair over half way.. but its around 0 degrees now..


i thought about an impact wrench with a LOOOONG torx bit would be the only way. It will probably strip it anyway..