96 k1500, 273k miles. 5.7 vortec.

My pickup is slow to heat this winter, and doesn't appear to get above 150 degrees engine temp. It's cold here, around zero degrees F these days, so subpar heating isn't great. Coolant was about a quart low, but that didn't fix it.

I have a few ideas: stuck thermostat is high on my list, or stuck fan clutch? Might also be water pump and need for coolant flush?

 

Bad water pump or needing system flush I would expect overheat. I would start by checking/changing thermostat. Doesn't hurt to do system flush if it's been a few years.

 

Definitely been a few years, I've owned probably ten years, not been flushed in that time

 

Starting it at zero just now, with fully cold engine, the fan was rotating fast, like engine speed. Should it be doing that?

 

I added cardboard in front of radiator to increase speed of warm-up. It did warm up faster, but temp gauge only reached about 150 over 20 minutes of driving.

I guess the temp sender and or gauge could be off?

 

If the gauge or temp sender were bad, the engine would still get to operating temp but wouldn't show it on the gauge and the heater would also blow hot air.

 

Heater does blow hot air at indicated temp of 150, just takes a long time to get there, and doesn't go any higher(at least since I've been watching, driving daily for a couple weeks).

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change the thermostat as Rednucleus said. the system should be hotter than 150 after 20minutes. Its the cheapest place to start fixing this concern. newer vehicles run a thermostat rationality check. if the coolant ins't up to temp by a set engine run time a p0128 dtc sets. you are obdII. if that code is present replace the stat 100%

 

Sounds like a thermostat to me.

 

Ok thanks, I'll start there.

Anyone here install a block heater? Might be another good addition, being that out sits outside, sometimes minus 20F or lower