Hey all - my thermostat housing (right beneath the distributer cap) decided to go belly-up and start leaking coolant all over my clutch/transaxle housing. Sweet. I ordered up a new thermostat gasket to toss in there and stop this leaky madness, and am not too worried about this, but; this will be my first time doing more than changing the oil on a car, and I'd really appreciate any feedback/advice on these coolant systems (easy/hard, quick/painstakingly slow, etc), or words of advice from anyone who has pulled the thermostat housing. It looks like all I have to do is disconnect a sensor, a hose, and two nuts and the whole assembly will just pop off...sound familiar?

Also....where the heck is the heater core in this car? I'm going to buy a Haynes manual tomorrow...

Changing a thermostat is pretty easy, same for the gasket.  Make sure to check that hose, if it's leaking, it could be the cause of the problem.  You may want to do a coolant flush along with changing out the gasket.  You may not lose much coolant from just changing that gasket, since it's higher up on the engine.  Just add some into the radiator after you've gotten everything bolted on, run the car and make sure the level doesn't go down too low in the radiator (and never take that cap off when it's hot, lol).

Though you can (and usually have to) have the radiator cap off when you've flushed coolant and refilled the radiator... the system will move the coolant through the engine, so the level goes down in the radiator as the car runs.  Then you fill it up with a funnel (or a steady-pouring hand), keep an eye on the level (but not with your eye too close, in case coolant spits out of the radiator).  Since you're only changing the gasket, though, you probably only need to run the car for a while, drive around, whatever, and when it's cooled down you check under the radiator cap.

I've flushed the coolant from both my del Sol and my LeBaron convertible, neither task was hard.  I used my Haynes (and in the del Sol's case, also the factory service manual) as a reference.  I need to check my All-Trac's thermostat and the coolant some time, because it looked awful clear to me.  NEVER run straight water in the coolant system!  It will cause rust inside the system.

Hope this helps out!

The thermostat is easy to change. It actually uses a rubber o-ring that fits around the thermostat to seal the housing. It's probably leaking because the rubber seal is cracked.  Remember that the "pointed" end of the thermostat faces the radiator hose. Also remember to snug the two housing nuts down evenly a little at a time. You'll be fine. Just take your time.

The heater core is inside of the car behind the dash. Sort of behind the radio. There are two heater hoses that pass through the metal firewall that feed it.

Also, don't even bother to disconnect the hose. Leave it attached to the thermostat housing.

I think I read somewhere here (or TN) that you should use an OEM quality replacement for the thermostat instead of a typical aftermarket auto parts store part (like Stant).  Is this really necessary?

Quoted from Rogue

I think I read somewhere here (or TN) that you should use an OEM quality replacement for the thermostat instead of a typical aftermarket auto parts store part (like Stant).  Is this really necessary?

I've never heard of that advice before but for things like the thermostat I tend to go OEM, although it OEM is more expensive.  Besides the dealer, you can try places like 1stToyotaParts, parts.com, etc.  1stToyotaParts is my preferred place to get genuine parts when I want them new; for used parts, I go to the local junkyard.