1992 Toyota overheating

dug1962 · 10-13-09, 05:24 PM

My truck is onerheating only when I have the heater on
Anyone ever hear of this before?
Otherwise it runs great
Its a 22re

calstyl2 · 10-13-09, 05:25 PM

Steam out of the exhaust?
Pressure out of the radiator?
4 cylinder or V-6?

dug1962 · 10-13-09, 05:29 PM

Pressure out of radiator

dug1962 · 10-13-09, 05:30 PM

4 cylinder 22re

calstyl2 · 10-13-09, 05:46 PM

Head Gasket............but I dont know mini's
Search using the search function

liljlandon · 10-13-09, 07:56 PM

Whats your compression? Milky oil/dirty antifreeze would be a quick way to identify this. Or, you have a blockage that is created when you turn the heater on.

2ndGenToyotaFan · 10-13-09, 08:55 PM

Does it only do it when you first start it up with the heater on? Or anytime you turn the heater on while driving? I bet you need the fancy Toyota dual thermostat....

corax · 10-14-09, 05:22 AM

here ya go, read this -> Toyota 4Runner and Pickup: Cheap Tricks

"After everybody looked at me like I was crazy for saying that it ran hotter with the heat on, I went to the dealership and bought t-stat part # 90916-03070. This did the trick. What happens on the 22R and 22RE engine, when the coolant goes through the heater core it gets cooled off enough that when it gets dumped back in on top of the t-stat it shuts it. Therefore the temperature in the engine continues to go up. The t-stat that I have mentioned has two valves in it, one at the regular temp. and one smaller on at a cooler temp. If the cool water shuts the big one, the smaller one stays open. The overshooting/spiking temperature gauge may aslo appear independent of heater operation."

2ndGenToyotaFan · 10-14-09, 08:48 AM

Thanks Corax, that's the link I could not find last night....

calstyl2 · 10-14-09, 06:49 PM

Did you figure it out?

dug1962 · 10-14-09, 06:50 PM

ok, thanks for all that good thermostat info. the truck has always run a little hotter with the heat on , but now its emptying about 25% of the radiator volume into the overflow tank and then all over the air filter box. after it cools down the overflow tank is full but the radiator is down 25%. the engine oil looks fine( no coolant mixing) and the coolant looks fine too. I'm droping it off to a trusted mechanic tomorrow, and will give him the article about the thermostat. Ill also ask for a compression test before he does a head gasket tear down.One other thing I did was a friend has a block tester that sniffs the radiator air to detect combustion gasses( carbon monoxide) and it checked positive --blue fluid turned yellow after about 5 pumps. also its dumping coolant with the heat on or off, when its off the temp gage never shows that its overheating.