[muppetz3]

Ok this is driving me nuts! thought i had a bad t-stat so i change it, put new coolant in. Start the truck, run it. Rad gets hot, i get head, i bleed the air. All is good. Take it to work, stays cool i have heat. Leave work, all is still good i have heat then BAM! heat dies, and temp pegs red. Rad is ice cold, coolant is boiling out overflow and still the rad is cold and no heat. Also truck starts to run like shit. Idel is all meessed up, keeps reving for a sec after i let off gas. Now i bet if i go back out there and start it, it will be freakin fine again. It keeps doing this to me. Works of for a day or so then BAM no heat and pegs red. Any idea what it could be? Air pocket from hell? Messed up head gasket? The pump is not leaking from the weep hole.
I just dont have a clue what to do, or what to check.
If anyone knows some nice tests i can do to figure out wth it is. Please let me know.

Muppet

 

[tuckn18s]

Check faq at top of page and maybe get a two stage thermostat from your local Toyota dealership

 

[zags]

You should still have heat with a bad t-stat as the heater hoses bypass the the thermostat. Sounds like an air pocket or head gasket pushing combustion gasses into the cooling sys.

 

[4CrawlR]

Ok this is driving me nuts! thought i had a bad t-stat so i change it, put new coolant in. Start the truck, run it. Rad gets hot, i get head, i bleed the air. All is good.

Hey, at least you are getting head :flipoff2:

Might try a pressure test on the cooling system, both to see if its holding pressure and to see if its getting pressurized by the exhaust. If that's OK, then there are chemical tests for detecting exhaust gas in the coolant. Mine did something similar when I had a small exhaust to coolant leak in the head gasket (due to a 0.008" warp in the head). Never had oil-coolant mixing.

 

[yotapwr]

mine did the same thing and it was a bad head gasket.

 

[bearitbilt]

Pop open the cap with the engine running, but cool (after like a minute or two). If it's got pressure behind it, then probably your head, or gasket is leaking severely. Sometimes cracks or leaks won't open up untill they get hot though, that's where the hydrocarbon test becomes handy.