High Temp weirdness

Hello,

Newbie to the forum and would appreciate a little help with some Taco weirdness. It has been fairly cold here in MT, about -5 F today. I was driving home from work and high water temp alarm came on in my 2018 Taco. Sure enough, gauge was just below red range as I was traveling 60 MPH in 5th. I pulled over and idled and the temp gauge dropped back to normal within 20 seconds and did not climb from normal/middle detent for the remainder of the trip- 15 miles home on the highway.

Any one have any issues like this? I am assuming it is related to extreme cold weather as the super quick reset of the gauge does not make any sense to me.

Thanks.

Lee

 

Sounds like a stuck thermostat that unstuck itself.

 

This

I would make sure reservoir is at proper level and burp the system in case it's low just in case, maybe get a cheap throwaway coolant tester from Walmart to test the coolant freezing temp.

 

Thank you gentlemen for your responses, I will follow through on your suggestions.

 

OR:
I've seen this before - coolant in the radiator turning into slush because of the cold, inhibiting flow through the radiator. This in turn increases coolant temperature in the engine. Not know exactly where the coolant temperature sensor is located in the system makes it difficult to confirm that this is the issue.
I've seen vehicles on our local interstate overheat in extreme cold because the coolant in the radiator froze.
Stopping and letting the engine idle for a bit decreased air flow through the radiator allowing the coolant to thaw and returning the temp sensor to normal.
-
EDIT: A corresponding symptom to this phenomena was no heat emitted from the interior heater core and a corresponding lack of windshield defrosting.
Might not be a waste of money to replace the thermostat.

 

Thanks for the response. I checked specific gravity of coolant and everything looks good. Took it to Toyota and they said it was the crack in the shroud and air was not being directed to radiator. I scoffed but they replaced it for free and no problems on the drive home. They performed pressure test as well. Next morning-no cab heat for 20 miles(in neg 8 weather) and engine getting hot again. Heat finally came on and engine stabilized to normal operating temp. I am sure I heard some sound movement in dash prior to getting heat in the cab so I thought it was air bubble. Coolant dumped from the reservoir again as well. I tried to burp the system and very little air came out of the radiator and thermostat was open as upper hose was hot but lower hose was ice cold while performing the burp. Oil looks okay and not milky, I can not see any other leakage anywhere. At a loss. Will go back to Toyota.

 

Bad thermostat.

 

Bad thermostat= when it finally opens and engine is good and hot/too hot, coolant rushes to radiator and excess blows out of reservoir? That seems to make sense to me but not to Toyota Dealer.

 

Be interested to know what they say then.

 

Err, spiking heat and blowing coolant was a headgasket leak in my second Gen. Gurgling behind dash was on the Toyota Mechanic symptoms checklist.

exhaust pressurized system and blew coolant, also caused temps to spike. Have them check coolant for exhaust residue. There is a test that shows if it’s contaminated.

 

Checking for contaminated coolant was also on my list for them to do. Thanks for the suggestion.

 

Here is the thermostat.... extra parts, extra complex, and extra failures are a possibility. Hopefully this covers the issue and you do not have further problems. Coolant temp is on the back of the cylinder heads.

 

Find a reputable dealer, look for lots of reviews, call corporate if you need to

A hot engine is...

 

Negative 17 last night. On a whim followed up on your suggestion. Pulled radiator cap and "boom" slush, despite my cheapo specific gravity tester telling me antifreeze was good to -32. I think we found the problem.

Thanks everyone for your suggestions. I have an appointment with Toyota tomorrow and may go anyways and have them flush system and check for exhaust products in the current system as well.

 

Mix was wrong....bummer

 

I'd honestly just flush the system myself and put in the best, highest rated antifreeze you can.

 

Use OEM or Pentafrost at the big box stores. Stay away from Prestone, Peak. If you can replace the thermostat too.

 

https://hellafunctional.com/?p=629

 

@stevesnj got it.

too much water and not enough concentrated glycol. The coolant was a slush and not circulating. Stopping the truck allowed it to thaw enough to become a liquid. It now was properly cooling your engine.

Get the proper coolent blend and you will be fine.

 

Something similar happened to my truck last week. Was on the highway and shifted down to 5th and not a minute later I was getting the overheating notification. Coasted to the nearest gas station and also heard some weird noise from behind my dash. I looked underneath the truck and saw that my front driveshaft, skid plate, and transmission housing was covered in coolant. The dealership had it for a few days and couldn't determine where the leak was coming from but they suspect it's some manufacturing defect and are replacing the short block next week. Pretty bummed out and pissed off honestly. It's a brand new 2021 with less than 4000 miles.