had similar problem with my 90 Runner. Ended up replacing the rad, replacing the t-stat three times. On the third replace I drilled two really small holes in the t-stat housing. Never overheated since.

IT was weird though, if I drove with the heat on full blast it would overheat very slowly. BUt as soon as I turned off the heat the temp would rise really quickly. You could also have a warped head, which would cause the engine to overheat as well. Good luck in your process.

 

After careful deliberation, let me be the first to say:
.
..
...
....................3.4 SWAP!




Sorry, I have nothing else useful to day I'm afraid.

 

Well NO DUH!

But that costs miney. A lot more than folks realize. A swap can nickle and dime you to death, and we JUST don't have that money right now. But yes a swap will be next time.

 

Yep, getting the 3.4 we have sitting in the garage prepped and ready for install is getting increasingly higher priority... I wish I had spent the last year or so that we've had the motor chipping away at all the stuff that has to be done!

 

No time like the present TC... just chip away at her a little each week and soon it will be done... just throw a few "house of wrenching" parties and it will be done in no time...

 

Interstingly, every time we open the HOW, none of our stuff gets done LOL

 

Hey everyone - for the record we figured out that the water pump was seized up, got that replaced and put it all back together (sealed a small leak on the swaped radiator from tippy) and Ron has been running since tuesday! We are so happy that was all it was!

 

Glad to hear you got it fixed... finally...

 

And hopefully this thread will help others who might run into same symptoms....!

Recap!

No oil in the coolant or via versa
Spark plug #6 was fine (no coolant)
Did the initial pressure test - saw the leak int he radiator and another we thought could be the water pump (but now maybe near temp sensor?)
Replaced the radiator.
Coolant pressure test held 13 PSI for an hour last night after replacing the radiator (but still had only water in there)
Drained the water, put coolant in, took it for a test drive last night. Seemed fine (albeit low idle still) and the heater was blowing hot - so heater core seemed ok.
Drove it this AM and it overheats again!

**********
EDIT From July 25th. We finally figured out the Water pump was seized. And I mean SEIZED! Replaced that, fixed the small leak in Tippy's swapped in radiator, the pressure held using the radiator pressurizer for an hour... put Ron back together and Ron has been running like a champ since this week!

 

Didn't I suggest the water pump here: https://www.yotatech.com/forums/f116.../#post51178966 ?

No worries. It's fixed now.

 

Probably . But we juats had to take things one at a time till we ruled everything out. No way to figure it was the water pump till we got the radiator leaks sorted....