I just replaced my radiator since my temp gauge was running hot. I did not replace my thermostat (I should have, but didn't) and the temp gauge is still running high, but I know the radiator isn't the issue.

Without draining all of my coolant, can I just detach the hose next to the thermostat housing, remove the thermostat, re-attatch the hose and re-fill the small amount of coolant I will lose...or do I need to drain the entire system again?

Also, it looks like installing a new thermostat is easy...are there any tricks?

My new Old Volvo last year gave me and two mechanics bad headaches when it started constantly overheating according to the gauge The first "idiot" even put a new thermostat in .... and then when that didn't work ... carved the core of the thermostat out and said my car probably needed a head job!!

A more competent mechanic used his thermo testing gun to see that the engine was running perfectly to spec even though the gauge was redlining....

later I've heard it's a common problem with this model of Volvo.

I still haven't fixed it as I found I could check the occasional heat spike by twiddleing with the wires behind dash... and the heat goes back to normal... I need to fix it soon as I did have a water pump seal go bad... and was falsely assumed that it was just the gauge going bad again... and noticed only after a short trip I was losing coolant..

If you're not losing coolant and heat of engine seems normal without steam coming out, you probably just have another false reading gauge ...(hint, does the fuel gauge read higher than what you thought you have in the tank... as they both use same voltage regulator... in my case just some electrical short maybe the culprit .....

I've also heard frequent water pump and or water pump seal failures are a Volvo 240 problem... one guy said every 40K miles he had to change his... I my records showed mine going after 40K too???!!!

Tom,
As others have mentioned you can drain the system down by using the petcock on the passenger side lower rear of block. I use an old piece of garden hose, cut to about a 4 foot length, 13mm wrench, and a catch pan. For the T-stat, 10mm wrench, make sure you get the rubber O-ring gasket that fits over the T-stat lip and you will not need any sealant. Make sure you scrape the crud out of the inside groove of the T-stat housing, and that the T-stat is in the groove and the housing is flush with the head before tightning.
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Bruce S. near D.C.

You can just drain out a little from the engine block petcock to get the coolent level below the T-stat.

That's the way I plan to do it when I repair the corroded head area where the 'stat is on my '84. Of course, I need a dry repair area for the JB Weld.

Best to drain the coolant properly and catch it in a container for re use (or binning) than letting it dribble out uncontrollably whilst you frantically try to free a seized in 'stat. You're gonna still have to top it up and check it for air, so why not jus to it in a relaxed, stress free and leisurely manner?

Regards,

Big Rich.
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'86 245, B230A. 161k. Old 200s never die, they just live on in other cars.

Make sure you have some RTV sealant. Funny that, I was able to replace the water pump and tighten it up.. no leaks (didn't even slice the mushroom gasket or the one for the metal pipe). But the t-stat... woah boy. I had to caulk that sucker up to keep it from leaking. If you haven't done your water pump recently, you might as well drain the engine.. replace the water pump and radiator hoses and the t-stat.

- alex

'85 244 Turbo

Tom,
Its as easy as it looks, and yes you can just remove the top hose. Replace what's lost, it won't be that much, of course make sure the engine is cooled down.
Good Luck.
Chuck
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Chuck Jaxel, Pine Hill NJ, Near Philly...