Cooling System Problem

Deep dive issue here...

I was about to go on a vacation starting with Overland Expo in Flagstaff last weekend. Engine overheated while in line at the drive up ATM. Took it to a local shop I've used for years with no problem (not a dealership).

Replaced the radiator as the mechanic said it was corroded on the bottom and was also partially clogged. It had 150k miles +/- on it.

Replaced the water pump as the flow rate wasn't where it should be. It also had about 150k miles.

Replaced the thermostat because why not.

Thought it was fixed. Yesterday drove it 60 miles one way(freeway and town driving) with no issues. It sat for a couple hours. Then drove it back home the same 60-ish miles with no problems. Until i turned in to my neighborhood and the temp gauge just spiked. Got it home just as the gauge hit vertical. The overflow tank was boiling but no leaks that i coukd find. No codes thrown. Drives fine.
Driving it back to the shop this morning and temp gauge, so far, is holding steady in the middle.

WTF!?!

 

How is the fan clutch?
A sign of a failing fan clutch is over heating at low speeds and idle.

 

Mechanic says it's good. It was replaced about a couple years ago.

 

Radiator cap? Air bubble in system?

 

Quite possibly an air bubble otherwise they may have to check for combustion gases in the cooling system

 

Clogging in radiator could mean clogging in water jacket too. Might need more flushing. Were you able to check the flow rate with the new water pump? Might also need a new heater core as shit goes where the water goes.

 

New rad cap. Did a block test, smoke test, pressure test, all negative.
Engine was rebuilt 150,000 miles ago because I got the trademarked Toyota head gasket leak back then.

 

They flushed the system and flow rate was substantially better after the new water pump.

 

If it was an air bubble, wouldn't the water pump have pushed it out of the system after running for that long?

 

The new thermostat may be sticking.

 

At this point, every new part that was installed is suspect.

 

Burping requires an open system. Usually done with cap off. Sometimes it leaves a void in top of radiator which you can re-top with coolant

 

Looks like we are going to give a new fan clutch a try.
Fingers crossed it works.

 

It was replaced a couple years ago.

 

Fan clutch didn't work. Still overheating at the lower rpms. Ran fine at highway speeds and 45 zones. Took it up Yarnell hill. It's a 9 mile grade speed limit due to turns between 35-45 mph. 3/4 of the way up the temp gauge starting going up.

Temp comes back down as engine rpm's increase.

Sitting at a burger joint waiting for it to cool down so I can check coolant levels.

 

I'd try backflushing the heater core and/or using an oem thermostat and water pump and water pump gasket if you have an aftermarket one.

 

Try pressure testing the new cap.

 

Would the use of a "universal" coolant instead of the pink Toyota rated stuff make this problem?

 

Coolant type doesn't really affect temp control.

At this point I'd be looking at headgaskets.

You won't always see smoke on Toyota failures, but what typically happens is the odd misfire on cold start, and pegged temps.

Are there any other symtoms?

 

About 150k miles ago I had the leaking head gasket. Ended up rebuilding the entire motor.
At the moment, there are zero codes being thrown, the vehicle runs very well (unlike when the gasket was leaking before), it's just a low rpm over heating issue.