Thermostat replacement


Apr 25, 2003
Guys, I've replaced Chevy thermostats in the past but, on the '87 G/N, do I just undo the bolt that holds the locking C clip and pull the housing out? Is there any silicone used here or any gaskets that I need or is there just a factory O ring that seals the coolant from leaking. How is this sealed from leaking?:confused:
you got it, one bolt holding that C-clip on, and all you need is that O-ring. but be careful, you may end up getting a new neck for that thermostat because if its the stock one it will be pretty fragile.
What Temp rating is a factory thermostat? 195F? And do I need a new O ring. I just had the thermo replaced in April. Is there a heater control valve on this car? Is the heater control valve the valve that goes into the heater core connection? This opens and closes when the A/C is either on or off, correct? Or should it move when the heater is on/off?
It's a 180. Most guys go to a 160.

Lots of guys replace that usually corroded, thin, weakened OEM neck with a billet aluminum or SS one. I recommend the latter.

Throughly clean the block and neck and use lots of Vaseline on the new o-ring. Careful not to cut or pinch the new o-ring on the install.

Something I do is stuff a paper towel under the nut so when you drop it you wont have to go fishing.:)

I'm never gonna finish this car!:(
Good point about dropping the nut, V6DVette. If you don't drop it the first time you take everything apart, you will the second time after you put everything together and it leaks because you cut the O-ring. Put lots of vaseline on your O-ring, to keep from having to make the change twice. By the way, if you had the thermo replaced in April, why are you doing it again?
Why? My heater core blew (fog mist in the pass floor side) so it was replaced. I don't have enough heat now. And I know that my car for the past 16 years had excellent heat after driving it for 2 miles. So I guess it's a bum thermo. I guess this car doesn't have a heater control valve either, correct?
I guess this car doesn't have a heater control valve either, correct?

Sure they do. Pass. side next to the coil pack.;)
Follow the heater hose.

I'm never gonna finish this car!:(
COPO....If your tstat is working (stk open or closed) your temp gauge should reflect it. Other wise it could be a bum heater control valve or bad vacum signal to the valve..i.e. the vacum controls inside max/nor/bi level/vent etc.
New heater cores even the GM ones don't put out heat like the old ones. :(

Don't ask me why.... :confused:

I doubt it's the thermostat.
Is the heater control valve the valve that is plugged into the heater core close to the fire wall? If so, it only moves up when the A/C is off and down when the A/C is on. It stays up when the heater in on heater and down when I turn the lever to off from heater. Is it suppose to go down when the heater is on?

I would look at the gauge in my Z28 but Buick was too cheap to put one in. If I install a Mech Temp Gauge, where is the best place to install it?