[dwolsten]

I just replaced the thermostat in my 94. It was acting similar to yours; it wouldn't heat up quickly, and would vary between 0 and 40%. I replaced it and now it acts like it used to: heats up quickly to 40%, and stays there.

The thermostat costs less than $10, and if you have an hour or two and can turn wrenches you can do it yourself. I recommend draining a gallon of coolant first to reduce the mess (if it's fairly new coolant you can put it back in afterwards; just use a clean container).

I would like to add, though, that they sure made the thermostat hard to get to. It's not impossible, but it took me a while with a straight 10mm wrench. It helped to remove the air intake tubing first.

 

[dwolsten]

This is just the question I was going to ask...about
getting to the thermostat. I guess dwolsten has a G3,
but I thouht they were at the end of the upper radiator
hose...and in G2s at the end of the lower hose.

I just attempted to do it last night, and could barely
get to the bolts to turn them...just barely. I ran out
of time and gave up. Is there some kind of trick or
hint or something? You mentioned removing the
air intake tubing first....do you mean totally, or
just at one end. I didn't want to remove the end
that goes to the engine for fear that I wouldn't put
everything back right.

The thermostat is at the end of the lower hose in the G3 as well; I think the differences between the B18B engines in the G2 and G3 are very minimal. I had a lot of trouble changing mine as well; I used a straight wrench, and just had to have a lot of patience. PITA. I tried a socket wrench, but mine were too large to get in there. I removed the air intake tubing entirely just to have room to work; it doesn't take long to do.

 

[dwolsten]

When I changed my thermostat, I just drained a gallon of coolant, which I reused afterwards. I don't recommend this unless you just changed your coolant; I had replaced my radiator a week or so before, and changed my coolant then, so I didn't see the need to throw out almost brand-new coolant, but if yours is old you should change it. To get as much of the old stuff out as possible, you should remove that drain bolt on the block. You can put a wide drain pan underneath to minimize the mess, but it won't be perfect. The fluid basically flows down the side of the block and splatters everywhere. It's not that much fluid though, if you've already drained the radiator. Have plenty of paper towels ready. The same thing will happen when you open the thermostat housing; there's a bunch of fluid behind the thermostat which the closed thermostat keeps from draining out when you drain the radiator.

 

[dwolsten]

There's no sealant. There's a rubber gasket that the thermostat fits into. You can reuse the existing one if it's in good shape, although the service manual says to replace it. Of course, the service manual always says to replace stuff like that, which I think in many cases isn't completely necessary.