Ok everyone new poster here. I'm having issues with a 2001 Tahoe I just purchased. Very clean vehicle with 175k miles on her but now that the weather is getting into the 20-30s every morning my Tahoe doesn't want to get to operating temperature. I already replaced the thermostat and that had no change in the running temperature. I drive 25 minutes to work each way and its usually 15 minutes of that trip is 75-80 mph in the interstate and it still doesn't get above 170-180 degrees

 

Welcome to the forum.

What temp. t-stat did you put in? I read once that they are only good for +/-20%.

 

A 185 t-stat. But the engine isn't getting hot enough for it to open. After I drive it the bottom hose is still cool like the thermostat hasn't opened yet

 

Not questioning anything, but you could have put the tstat in backwards? Or perhaps the new tstat is bad.

 

No thermostat isn't in backwards. The one for this Tahoe is a housing with the thermostat made into it.

 

Put it in a pan of water w/ a thermometer in it and raise the temp. of the water 'til it opens. I'm betting on a faulty t-stat. Not that unusual.

 

Thermostat isn't really the problem. I can drive for 20 and the engine not get to 175. So even if it was stuck open it may be a different problem that I'm not familiar with

 

Put a piece of cardboard in front of the radiator, covering 1/3 or so, see if the engine temp gets up.

 

These tstats might be fail open, could be partially open when it should be closed.

 

Does the heater blower hot?