There are two thermostats for the B21, B23 and B230 engines. One is 87C and usually for the turbo variety, the other is 92C and is for n/a variety. They are a low cost dealer item.

The labor involved in checking it out is the same as for installing a new one. The 92C is, to me, preferable as it keeps the engine more efficient and a little hotter (and also my feet - when needed).

Coupla tips on this job. (1) Drain out just a little coolant, I usually unhook the clamp on hose on the bottom of the overflow tank and loosen it. Pull the hose, have a clean container handy to catch what runs out of the tank and also use the other hand to hold the hose end above the level of the tank. When the tank has drained, lower the hose end into a clean container (same one) and drain that out. If you get a whole gallon out, that's enough. Unless you are changing the coolant too, use the saved stuff again.

(2) Next pull the upper hose off the thermostat housing. Tuck it out of the way. Remove the nuts on the housing (10mm) and pull it free. There may be a little coolant runout.

(3) Pull the thermostat out and have a look. If it looks OK, save it for a good spare. Clean the housing and the head. IF you use a RAZOR knife to clean the block be EXTRA careful as the razor steel is so much harder than the aluminum that you can accidentally carve off slivers of AL.

(4) Put the new gasket on the new thermostat. No sealant is necessary. (vaseline can decay some types of rubber.) Be sure that the little wobbly bit through the thermostat flange is at 12 o'clock - it allows air bubbles to get out. Then slip a string loop in the housing, through the thermostat, back out through the housing and pull the thermostat up inside the housing. Put the housing down on the studs and pull out the string. Easy, right?

(5) Don't forget the lifter loop and the a/c hose standoff when putting the nuts back on. Don't over torque. The housing is pot metal and easy to crack. Just tighten them evenly.

(6) Clamp everything back up - remember the one on the bottom of the overflow tank Put in the coolant, and start the engine. Afer the thermostat opens give the upper hose a couple squeezes to get air bubbles moving out.

That ought to do the job.

Good Luck,

Bob

:>)


PS - If all this seems "talking down" to you, sorry.