Thermostat Removal

[Hooked on Deanna]

Thermostats, Good News and Bad News...

Well my 1993 175 hp mecurs' have 2 thermostats on each block at the top of the cylinder heads. Each stat housing has 2 screws for a total of 8 screws. I had 2 of the 8 screws wrench off (seized up, Bad News). The stats look shot; full of white powder buildup and corroded. The hoses, 90 deg fittings, and housing look good (no build up in them!). The cylinder chamber viewed from the stat opening looks clean! (clean cooling passages, Good News!).

Now I have to figure out the best way to remove the broken off screws. The screws broke at the head so I have plenty of vise grip area. I plan on soaking the screws with a high quality penetrating fluid. This is a minor issue if I can get the screws out without stripping the aluminum cylinder head. I believe I should heat the area to take advantage of the expansion difference between aluminum and stainless steel. The threaded hole will expanded more than the stainless and should make removal easier. Any comments???

 

[hkeiner]

Re: Thermostat Removal

I am not sure about the physics of heating the aluminum block and bolt at the same time to loosen the broken bolt. However, I would suggest the following methods first:

- Soak with Liquid Wrench or PB Blaster or equivilent
- Weld bolt or nut to protruding end of broken bolt
- Quickly heat the area around the bolt and not the bolt


Also, I suggest you use vice grips before using an easy out as easy outs may expand the bolt diamater a bit and make removal even harder, and if it breaks off you are really in deep ####.

Others may have better success stories to share...

 

[Chris1956]

Re: Thermostat Removal

OK, Heat up the bolts with a torch. remove the torch and apply PB Blaster. Sometimes it will soak in, due to the cooling and allow the bolts to free up.

 

[Hooked on Deanna]

Re: Thermostat Removal

Heated the bolt and sprayed with PB blaster. Allowed it to sit for 2 hours. Locked down vise grips heated again tried to loosen with no luck. Getting worried that this is going to turn into a big job! Will get a tig welder (where?) and try that method. I didn't like the vise grip idea because I've had mixed luck over the years gripping threads to remove broken screws. I don't have the long nose type vise grips, are they better for this task?

 

[Chris1956]

Re: Thermostat Removal

Sorry to hear about your troubles. Are you getting enough twist from the vicegrips? You can substitute a small pipewrench if necessary. Did the PB Blaster get sucked into the block, around the screws when you removed the heat? You might let it have more time to soak. Tap the bolt ends gently to vibrate them a bit.

 

[Hooked on Deanna]

Re: Thermostat Removal

Thanks...This really is a pain in the %$#@!

I was able to get a nut on the stripped threads and have decided to wait to see if I can get the nut welded to the remaining thread. I figure now is not the time to rush. I just need to find someone with the right welder.

The PB blaster penetrated I think, but I'm afraid that a pipe wrench will end up snapping the stud off. And. the concern the pipe wrench could gouge the seal surface.