Hey, I have a '92 yota truck and have rebuilt the whole motor. When i start the truck cold it heats up like normal and warms up normal and even stays there for about 5 minutes or so. But then suddenly the temperature starts climbing and the only way to keep her from overheating is to turn the heater on full blast in the truck. When i blast the heater it hovers around the normal mark sometimes going up a bit and sometimes sitting normal. I read a warning on some toyota website that if you put the headgaskets in backwards it blocks a coolant channel. Im pretty sure i didnt do this but not positive. Any ideas? vapor lock?

 

I read on another thread that you could have an air bubble in the system. You could have the T-stat in backwards. You could run it without the T-stat and see what it does. Do a compression test. Buy a kit that checks for combustion gas in the coolant system. A clogged radiator.

Let us know what you try, find or what the cure was.

Harry

 

That was the first thing that I thought of. If it is that, I've heard removing the t-stat helps.

 

If you know which way you put the headgasket in I have some pictures from my install that might be able to tell you if it was done right or not. I wonder if there is some lip or something on the HG that will tell you which way it's on?

 

Backwards yes. I've done it learned my lesson. Change it be done with it.
They are labeled left and right bank.
This would be if you are sitting in the truck so if you are stoned putting it together it's easy to screw up.

 

Top off the cooliant level and run the truck with the radiator cap off for a few minutes. This will help get your "air bubble" out.

My 1988 had a "bubble" in the cooling system and it would cause the heat to not work every so often. Talk about an easy fix, however it took me two months to figure it out.

 

would that explain the overheating? it doesnt though if i run my heater on full blast. I lifted the front of my truck and ran it and a few bubbles came out and it actually took longer for the heat to start climbing. im pretty sure i just assumed it would be from looking in the engine left and right so they probably are wrong.

 

Toyotas are known to trap air in the sytems. Burp it again till you are 100% sure there are no more bubbles. If it comes back theres a leak somewhere....

 

Park on an incline with the front high. With the engine cool, take off the radiator cap & start the engine. Let it run for a minute, then start adding coolant until it tops off. Let it run until warm, the top off any more if it needs it. Put the cap back on. That should fix your problem IF it's the coolant air pocket. If not, you've got other problems. A thermostat either works or it doesn't. Did you install a new one when your rebuilt the truck?

 

yes new thermostat, i tilted the engine up for quite some time but ill try it again.

 

What temp t-stat did you use?

 

im not sure (i guess i should check these things) the guy at canadian tire looked it up on the computer and gave me the standard

 

also check your fan clutch. if its not engaging , it will overheat.

 

No, that fan is only used in pretty extreme cases. Under normal driving and temperature conditions, my fan is NEVER on. It's easy to hear when it angages, and for me it only happens when it is very warm outside.

 

Ok i took it for a long drive today after sitting it all night with the front end a foot and a half higher and there was no trapped air when i started it. But the drive it took about 3 minutes from warm for the temperature to start climbing. I then turn on the heater full blast and it usually keeps her at normal. But i found that it stayed just over half for the most of my drive. but it did climb as high as just before the black gap between the white and red marker and there was no real pattern but if i was idleing and it got that hot i would rev it to 4k and it would drop very fast as far as a temperature sensor goes. The whole trip it seemed to bounce around between just over half and just before the gap. Any ideas?

 

ok what about this when its idling it heats up, when your driving it below 3k it heats up. When you have the clutch in or have it in neutral with rpms between 2500 and up it cools down and the higher rpms it has the faster and more it cools....

 

I feel your pain. I began having very similar issues about two months after having the head gaskets replaced. Everything on the cooling system checked out, but it was running hot, even boiled over once. Finally removed the thermostat altogether (after replacing it twice). That was 5K miles ago. Doesn't overheat, and as long as the outside temp is 55-60 or above, it gets up to operating temp after 5-6 miles. I don't necessarily recommend this, but in my case it was the only way to keep my truck on the road.

 

Sounds like a bad fan clutch is a possiblity to me.

BTW my factory water temp gauge doesn't start moving from the middle until the coolant is around 240* F. So be very careful using that as a gauge of what is normal, its really more like an idiot light than a real gauge. Hope you have good rad pressure and coolant or you will be boiling real fast, at least localized boiling on the head hot spots.