Heat and Temp gauge problems

99 monte carlo Z34 3800. I am not getting much heat inside of my car. The temperature gauge only goes up to about 125-135 degrees when the car is warmed up. I noticed that when i turn the heat on, the temp will drop back down to around 100 or so. The heat will get slightly warm, but never any hotter than that. I have replaced the thermostat twice, but still no luck. Not sure what the problem(s) may be...

99 monte carlo Z34 3800. I am not getting much heat inside of my car. The temperature gauge only goes up to about 125-135 degrees when the car is warmed up. I noticed that when i turn the heat on, the temp will drop back down to around 100 or so. The heat will get slightly warm, but never any hotter than that. I have replaced the thermostat twice, but still no luck. Not sure what the problem(s) may be...

when replacing the thermostat, the rubber seal must be replaced in addition to the gasket...so thats three parts....the thermostats must be high quality type ..not the cheap junk...after replacement this coolant system needs bleeding at the gooseneck bleed screw....if the system is not bled it will give your problem as well as a bad/defective install/thermostat...

this is a good engine with few problems if the coolant system is properly maintained with dexcool...mixing coolants will damage the engine and its all over...as it will leak out every where....

1998 monte carlo Z34 130,ooomi....no problems

Thanks for replying to the post, but I don't believe it was the thermostat. I just put in a brand new AC Delco thermostat, and bled the system. Temp gauge is still in the 130 degree range, and the heat is only slightly warm when the engine is warmed up.

Thanks for replying to the post, but I don't believe it was the thermostat. I just put in a brand new AC Delco thermostat, and bled the system. Temp gauge is still in the 130 degree range, and the heat is only slightly warm when the engine is warmed up.
what about the gasket and rubber seal for the thermostat...coolant is bypassing the thermostat....

you must not just replace the thermostat...all the components will insure the coolant will not bypass the thermostat....

Yes I replaced the seal that goes around the thermostat. I don't know what you are talking about with this other gasket. There was no other gasket there when i replaced it the first time. I asked at the shop and they just said to replace the thermostat and seal. I have even looked online and the thermostat seal and the thermostat gasket are the same part numbers, so i'm assuming there's only one...

Yes I replaced the seal that goes around the thermostat. I don't know what you are talking about with this other gasket. There was no other gasket there when i replaced it the first time. I asked at the shop and they just said to replace the thermostat and seal. I have even looked online and the thermostat seal and the thermostat gasket are the same part numbers, so i'm assuming there's only one...

there is a rubber gasket that goes into the thermostat radius...then the goose neck fiber gasket goes on top of that ...you put some gasket sealer on the fiber gasket and then torque the goose neck down....

there is a rubber gasket that goes into the thermostat radius...then the goose neck fiber gasket goes on top of that ...you put some gasket sealer on the fiber gasket and then torque the goose neck down....

edit : thermostat superstat st 5482321 #45849 $10.84
GASKET THERMOSTAT HOUSING 5186021 # 35595 $ 0.98
WATER OUTLET gasket 5180355 #35666 $ 2.44

so this is the list advance auto parts......if one is not in you area cross these part numbers over...

also new does not mean good...always place new in a boiling or almost boiling pot of water held by a small wire and observe that it just opens when the water just starts to bubble and use of thermometer is very accurate.... at 195 f it should be open a crack...not fully open..

I always test new no quality any more...