Temp gauge goes into red but everything seems normal

I get in the truck this morning, 1st time it ran since 7pm yesterday, i go about 1 mile, make a stop, get back in truck, and notice i have no heat, blowing cold air, but temp gauge is at running temp, put selector to defrost and the air circ light comes on. Go's off if i direct heat to other spots, i go another 2 miles and all of a sudden temp gauge shoots up into the red, but truck sounds, and feels fine, no steam from under hood, but still no heat. Go in store for 5 mins, come out, open hood and feel radiator lines, they're hot, bit normal hot, start truck and temp gauge goes up to running temp, and holds there, Leave and in about 1/2 mile, temps gauge goes back into the red, again, truck feels and sounds fine, no steam, i have about 3-4 mile drive to home, and about 1/4 mile from home, temp gauge goes right back down to running temp, then 2 dash lights come on, the check engine light, and some trac off light. Actual temp seems fine, no boiling. Anyone ever seen this or have any idea what i should be looking at??????????

I have a 2012 Tacoma, 4 cyclinder, 4WD

 

Any coolant smell?

 

Stuck engine thermostat?

 

No, no coolant smell.

 

My thought also, but the check engine light and trac off light baffles me. And also the air circ light for the AC coming on when i put it to defrost.

 

Did you check the level? Sounds to me you are really low on coolant.

 

Maybe the heater core is going bad.

 

thermostat or temperature sending sensor

 

Just checked was definitely low. If my heads or gasket was bad, wouldnt the coolant be in the engine oil? Checked the oil and it is totally clean, im thinking a coolant leak in a hose or something

 

Traction lights come on when the check engine light is on regardless of the code. Stop by any Autozone or the like to get the code, should narrow it down. If i was a betting man I would guess it would be a temperature code.

 

Lower radiator tank leak?

Do NOT assume the sender/gauge are wrong. Assume they're correct and don't drive the truck until it's fixed. This could turn really expensive if not taken *very* seriously.

 

This doesn’t exactly help your current situation but it’s why I have an ultra gauge. It will tell you your exact temp in real numbers rather than relying on the little gauge on the dash. Just helps you be more aware of what’s going on with your truck by monitoring different things in real time.

good luck with it, and I hope you didn’t warp a head by letting it get too hot.

 

YES! Definitely! Never second guess warning lights without a thorough checkout.

 

If the thermostat was somehow stuck shut or if you were super low on coolant, I don't think you would get any heat. Even if the engine was super hot

 

I'd bet it's a head gasket or other failure internally and you are burning/blowing the coolant out the pipe.

That's why the oil isn't contaminated

Or, its weeping out the water pump seal, or other leak and you havent noticed it

I'd take a light and start looking around the engine and radiator and hose bottoms and see if you see a line of wet or dried coolant.

 

No, not always.

I had the heads rebuilt and ended up with the exact same problem it had before because it had a cracked block. $1,800 down the drain.

You're going to need the code read.

 

Doesn't the UG rely on the same sending unit the temperature gauge uses? So if the gauge is getting corrupted data the UG would also?

I don't have a UG so I'm not sure how they get data.

 

I added coolant and did a few starts and the chk engine light and trac light went out, let it run a while untill temp gauge showed running temp, but still no heat, also, hose from t-stat is still cool, thinking t-stat is shot.

 

Good Work! I think you're on the right track - keep us posted.

 

What age / mileage was the coolant at in the truck prior to you adding?