Low engine temp after radiator flush

njs2247 · February 21, 2019

So I had my radiator flushed almost a month ago and noticed my engine temp consistently running low, between the 210 mark and the mark right before it. Well today it was hovering around the mark before the 210 mark and sometimes even lower.

Just wanted to ask you guys if there's anything else I need to be looking at besides the thermostat? Also, truck has 117k miles on it, so would replacing entire water pump with thermostat be a better option then just replacing the thermostat?

1SLOW1500 · February 21, 2019

Those numbers are perfect. I wouldnt worry.

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Sierra Dan · February 21, 2019

Yeah..... that is in the normal operating range.

There was a TSB on some of the earlier '14 and 15' K2 trucks about a cycling thermostat causing radiator stress fractures.

Since you have a '14, your thermostat may be doing this. Have you noticed any coolant evaporation or low coolant in the reservoir?

I had my Radiator and thermostat replaced under warranty for this.

mookdoc6 · February 21, 2019

It should be sitting right at Half way mark when up to temp. Go buy the T-stat and housing along with a new Upper hose...total cost 80.00 change it yourself. If your way below half mark after that investigate further.............

SS502 · February 21, 2019

Unless you're losing radiator fluid, re-read @1SLOW1500 post above

MRW412 · February 21, 2019

My truck went in for warranty work because the passenger side lifters failed, which required them to remove the radiator. I got my truck back about a month ago and the engine temperature gauge has been doing the exact same thing as your describing. It fluctuates between 190-210 constantly. Before I took my truck in, it would stay perfectly at 210 all the time. I've tried purging the radiator to see if there was any air stuck in the system with no luck. Let me know if you find out what the cause is.

4weight · February 21, 2019

29 minutes ago, SS502 said:

Unless you're losing radiator fluid, re-read @1SLOW1500 post above

That is what I would do, so do nothing. It's good.

Mike GMC · February 21, 2019

Does it seem to take longer to warm up? Does the heater still work properly? If those are normal, you're probably good.

njs2247 · February 21, 2019

Thanks for all the suggestions guys. The temp worried me because the past 4 GM trucks I've owned have all run dead center @ 210 for engine temp. And I swear I've read somewhere in these forums that these engines perform best when running at 210.

For some reason I've always had bad luck with water pumps on all my trucks, so I might just go ahead and switch out water pump with thermostat and if problem stays the same then I can live with it. If it goes back to "normal" then I'll know something was up.

njs2247 · February 21, 2019

You know Mike, when defrost and heater are on, the temp fluctuates like crazy. Warm to cool to warm and so on. Even when I want to blow a little warmer air through front facing vents, it fluctuates. I'm constantly having to adjust it. Sometimes it's a crazy fluctuation and sometimes is a minor one.

Can't believe I left this out in my original post.

Mike GMC · February 21, 2019

Sounds like air in the system to me. My 2000 doesn't fluctuate, but it just won't warm up when it's below about 20 deg.F. I can even hear the air in the heater core occasionally. It could also be the Tstat. Wouldn't hurt to replace it.

Sierra Dan · February 21, 2019

3 minutes ago, Mike GMC said:

Sounds like air in the system to me. My 2000 doesn't fluctuate, but it just won't warm up when it's below about 20 deg.F. I can even hear the air in the heater core occasionally. It could also be the Tstat. Wouldn't hurt to replace it.

Air in the system from my cracked radiator caused mine to fluctuate.

My dealer explained this cause and effect to me in detail.

So I agree with you Mike.

Hence my comment on the OP checking his radiator for cracks and reservoir level since his is a '14 model.

Early '15 Tahoe, Yukon and Suburban models also had the same flaw.

njs2247 · February 21, 2019

Dan, where about on radiator are the cracks happening? I've yet to smell any coolant, but I'll take a look and see if I see anything.

SS502 · February 22, 2019

6 hours ago, SS502 said:

Unless you're losing radiator fluid, re-read @1SLOW1500 post above

4 hours ago, njs2247 said:

Dan, where about on radiator are the cracks happening? I've yet to smell any coolant, but I'll take a look and see if I see anything.

So are you or are you not seeing the fluid level dropping? Obviously we missed the fluctuations in your original post...but if you’re not losing fluid you shouldn’t have a leak, maybe air in the system but no fluid loss equals no leak.

mookdoc6 · February 22, 2019

5 hours ago, Mike GMC said:

Sounds like air in the system to me. My 2000 doesn't fluctuate, but it just won't warm up when it's below about 20 deg.F. I can even hear the air in the heater core occasionally. It could also be the Tstat. Wouldn't hurt to replace it.

I would go T-Stat route....and upper hose...Yeah, I am still a hose freak anyway?