Engine not reaching operating temperature

Ugh. Today was a real challenge for my Tahoe it seems. It was 32 F this morning and the coolant never reached half way on the gauge (about 175 F according to my scan tool). I drove about 3 miles, let it idle for about 15 min and it still didn't reach operating temperature. I even revd up the engine to 2000 rpm for a few minutes and it still didn't budge. I actually saw temps drop a bit. So I decided to see if there was anyway to check the cooling system per the repair manual. Maybe there is something in there with troubleshooting steps or perhaps a time vs temperature plot? Maybe there is something that tells you if it is taking too long to warm up? Well I looked and depressingly found only basic information. The only thing I found was this brief troubleshooting guide. Needless to say there needs to be a better way to check a cooling system other than making the technician take out the thermostat and check it in a pot of hot coolant. Have things improved any with more late model vehicles?

Honestly I'm not even sure it's worth pulling the tstat to test it

That's pretty well indicative of a bad thermostat. There's literally nothing else that would cause it unless you're some absurd -60 degree weather or something where just the air passing over the engine bay would cool it

Test and or replace your thermostat. If still won't heat up, cover the grill up like the big rigs do. The K2s have shutters too I think, some of them anyway. I know a guy on another forum who has covered up a large portion of his grill already.

swathdiver said:

Test and or replace your thermostat. If still won't heat up, cover the grill up like the big rigs do. The K2s have shutters too I think, some of them anyway. I know a guy on another forum who has covered up a large portion of his grill already.

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Thats not a bad idea for an engine with a belt driven fan...but I have an electrical fan. It doesn't run until coolant gets to 225 F. So airflow cooling down the radiator isn't the problem. It seems more likely that cold coolant in the radiator is flowing into the engine via a bad / stuck open tstat.

Matahoe said:

Thats not a bad idea for an engine with a belt driven fan...but I have an electrical fan. It doesn't run until coolant gets to 225 F. So airflow cooling down the radiator isn't the problem. It seems more likely that cold coolant in the radiator is flowing into the engine via a bad / stuck open tstat.

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My comment was mean as an If/Then statement. It's very likely a thermostat problem. Always better when they stick open than close like the old days!

A thermostat stuck open is almost like not having one. It can foul plugs and run rich for what they cost and little time to install

Ok. Looked at the temps again this morning. This time i turned off the front and rear heater fans and it warmed up within 15 minutes at idle. So now there seems to be no problem

Great just keep an eye on your coolant level and if the temp drops when you turn the heat on. Heater cores leak where you can’t see them. Just helped a guy where the hose going into the core was warm but the one going out was cool. Heater core was clogged. Good luck

eh, I would say it is more likely the thermostat was not stuck this time, I would go ahead and replace the thermostat anyway. running or not running your heater fans will not make any difference if your vehicle gets up to normal operating temperature or not

Matahoe said:

Ok. Looked at the temps again this morning. This time i turned off the front and rear heater fans and it warmed up within 15 minutes at idle. So now there seems to be no problem

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The heater cores are like mini radiators and will cool down the engine if the blower fans are running. But your engine should be warming up enough even with the fans on if the thermostat is the right temp and working properly (unless like @SnowDrifter said you have crazy cold ambient temps).