I suspect I have to replace the thermostat in my 95 850, it's just not heating up like it should. 2 questions.... do I need to drain the antifreeze to lower the fluid level? And, is there a gasket needed. I checked out the proceedure on Bay 13 and he covers a few things in the example. One thing he didn't mention is a gasket which is the reason for the question. Thanks for any comments.

Thom

It seems none of you guys use any sealant around the gasket?? I've replaced four T-stats, two on 850s, and two on 960s (same basic engine), and always used a thin layer of Permatex Blue RTV. I've also always used a thin coat of sealant when replacing thermostats on other cars. How come I don't see this being recommended on the Volvo forum?

There is a split O ring that does the sealing it attaches to the thermostat and is compressed by the housing

Get the correct size torx bit. Thermostat with o ring about $8-9 at a parts store. Total job time about 15 minutes. No need to disconnect hose, just bend out of way. Don't bother to drain coolent, just top up after replacement.

Simple job...

that wraps around the rim of the thermostat.

NO gasket needed for the housing itself.
(Some other cars use gasket around the housing, but not on the thermostat itself, such as BMW 1985 735 car).

Hope this helps.

cn

Here's a link to a step-by-step: How to Replace your Thermostat (with photos)
http://www.matthewsvolvosite.com/tstat.php

--
Ken

Thanks.
Thom

I have 2 850s and have replaced 4 thermostats so far (you get about 80,000 to 100,000 miles before they fail)

If you don't mind a little spillage - maybe a 1 cup, less if you are quick - no need to drain coolant as on http://www.matthewsvolvosite.com/tstat.php Although if you haven't done a fluid change lately not a bad idea. But if you are looking to do change the t-stat quick only takes a few moments to do it (but wait for engine to cool first!)

And I agree that a torx socket bit much better then screwdriver type and less likely to strip the torx bolt head.

Good luck!