Cooling system problem...with a twist...

Hey all,

I know there are some other threads about this topic, but the suggestions given didn't work for me:

I have a 2000 Monte, 3.8L (SS), and not long ago the check engine light came on, but went away later that day. A week later the temp gauge stopped working completely. I replaced the coolant temp sensor and it seemed to work fine. Then I noticed that the car wasn't warming up enough (low temp and wouldn't go into overdrive). So I replaced the thermostat. Well, that didn't work. So I replaced it again, hoping it was a defective thermostat. Seemed to work great! When parked and with the Rad cap off (or on 1/2 way), the car warmed up to the normal temp. But: when I start to actually drive it, the car cools back down completely (almost to being as cold as though I never drove it). Does anyone have any ideas? I've been told it could be a clogged heater core (but I have heat when its warm, so that's out), a clog in the rad or the temp sending unit (not the sensor). Again, any ideas? I'd appreciate it!!

when the thermostat was replaced did you use a new gasket and rubber seal? test thermostat in boiling water see if it opens and closes properly use a thermometer...recheck the ect sensor and connector/wires for damage corrosion...use a ohm meter check for the correct temperature /resistance relationships..on the ect..

this coolant system is dexcool only...if its not then it is possible that things are pluged up..