I'm about to replace my thermostat to try and conquer a high temp reading I've been experienceing. I notice there's a blue sealant (RTV of some kind?) around the base of the housing where it contacts the engine. Since I want to have all the necessary stuff on hand when I do this, can someone tell me what it is I should use when replacing the housing? The instructions in the valve package don't mention anything about sealants or gaskets--it just says to replace the housing. Thanks.

-Chris Throop
'93 245

A few last tips:

1) Remove ALL the sealant from the housing and the mating face on the head. Use a razor scraper with great care. The steel in the razor blade is harder than the aluminum in the head, so with not too much effort you can carve off bits of aluminum! I use a flat-tip screwdriver. Same tool on the housing.

2) Drain a little coolant first. I usually loosen the lower radiator hose from the radiator, and carefully open up for a short time. That's to get the coolant level in the head lower than the thermostat level. You will need to replace the coolant. Easier yet is to do a coolant flush concurrently with the thermostat replacement.

3) Before you remove the housing from the head, remove the upper hose from the housing. When you are ready to install the new thermostat, run something through the housing so you can pull the thermostat up into the housing and hold it there while installing. You can then pull out the string, or whatever you used, and connect up everything.

4) Fill coolant and run until the thermostat opens. Have the heater control on full hot to flush that core too.

5) Add coolant as needed, and squeeze the upper hose to burp out air bubbles.

6) Remember that coolant has a smell that can attract critters that will drink it...and die.


Good Luck,

Bob

:>)

Chris,

As the other guys said, use PB blaster. In fact, this stuff is wonderful for any hardware removal situation where corrosion or rust might be an issue. Apply some to the holding nuts and studs the night before you attempt to remove the t'stat housing. It will lube things up nicely. As the other guys have noted, it's easy to break a stud either removing the housing or installing. Be careful.

Good luck, again,

Marty
--
93 244 175K, 93 244 109K, 93 245 115K, 99 V-70 84K

I ve gotten in the habbit of using PB blaster on almost everything I do, its truly lives up to its reputation. Snapping the studs for the thermostat would be a very bad day. A note on the other post, I dont think WD-40 is really a pentrating oil, its great for all the uses its intended for, but not a substitute for pentrating oil.

All good posts - PB Blaster or WD-40, and turn nuts gently at first to loosen.
I broke off the top of a stud and had just enough thread left to hold the parts on when done.

Small jiggle pin in hole in thermostat goes on top side, true. Also goes at highest point of top side - it's a kind of vent to handle air pockets; that's my understanding. Air bubbles rise and eventually exit via small hose at top passenger side of radiator.

Again yes re. rubbber gasket. Wraps around t'stat, that's all. Makes a good seal.
--
[aka Sophie's Maintainer] Sven: '89 245, IPD sways, E-fan conversion, 28+ mpg - auto tranny. 850 mi/week commute.

Just a suggestion, the studs are small, use PB Blaster or other penetrating oil before removing them

Hello Chris,

Having done this before and not screwed it up (as far as I know), it is not a difficult job.

You do not use any sealant at all. Just make sure the gasket surface and thermostat housing is very clean. Make sure you scrape off all the old goop. I use a single blade razor for the block. Put a clean rag in the hole to ensure no goop or debris goes down the block.

Also, make sure you install the thermostat with the jiggle air valve pointing up. And lastly, be careful tightening the housing nuts as they don't take a lot of torque as the rubber gasket makes the seal with very little pressure.

There has to be a zillion posts on this subject as well as info on the 700/900 FAQS. Do some reading before you start the job.

Good luck,

Marty Wolfson
--
93 244 175K, 93 244 109K, 93 245 115K, 99 V-70 84K

Thanks, Marty. Just to clarify one thing: the gasket that you mentioned is the rubber gasket that comes with the thermostat, right? The round one that encircles the thermostat itself?

-Chris

Yes, that's what he meant.
This setup is different then what you may have seem in the past. There is no cardboard gasket, it is this rubber 'O' ring that fits onto the Thermostat.

Easy on the tightening , as mentioned the Snap sound of hardware breaking is not what you want to hear on this 15 minute job.
--
'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me

Thanks for all the advice everyone. I think I'm well prepared now!

-Chris