What temp is the gauge supposed to read on an '89 4.3 vin Z engine when the engine's at normal temp and the thermostat's not stuck open? I just replaced my t-stat because my heater core blew out, and now the temp's going about a couple needles width above 210 but not pegging like it was when the heater core first blew and shot coolant all over the inside of the truck. It used to read just barely above 100 when the truck was running and had been running for a while (as in, gotten to normal temperature).

So, was it running way cold all this time, or am I still having an overheating problem?

 

The stock thermostat should be set to regulate the temperature at ~195F. That should result in a gauge reading of 200-210F.

 

so it could be a little of both. it may be running a bit hot (possibly low coolant still) and it definitely WAS running WAAAAAAY too cold before.