i have an 1988 4runner with a 22re,having an over heating problem. i just recently rebuilt the motor. it DID NOT over heat before i rebuilt the motor. the head has been pressure checked, cleaned, and surfaced, it has a toyota thermostat in it, brand new water pump, block was cleaned and magnafluxed (spelling) radiator was takin to a lock radiator shop, they did a flow test, that was all, and passed, clogged? temperature sending unit is new and from toyota. no water in the oil, over heats on the highway, in town and at an idle. has fan shroud. all new hoses, intake was resurfaced, have tried after marked gauges to insure the over heating. truck runs great, so pretty sure timing chain is correct, entire motor is new parts minus the crank and cam and head. if you have a suggestion or idea please let me know, because i am at a stand point and dont know what to do at this point

 

New thermostats are bad all the time from what I've heard. I'd take yours out and put it in hot water on the stove and see if it's working properly. Since it's overheating all the time at all speeds I'd say you got a bum thermo. Probably not opening at all.

 

thermostat is good, i did throw it in a pot of boiling water, made sure it was suspended, and also put a canning thermometer on the pot to see when it opened, did open at 180

 

Is it just the gauge saying it's overheating or is it boiling over? You mention aftermarket gauges but not what they tell you.

If the thermo was working right..? I don't know, you must have some kind of flow problem or maybe your radiator cap is not holding pressure. Is the cap new?

Not to be condescending but are you sure you installed the thermostat in the correct orientation? I'm not that familiar with the 3.0 so I'm not sure if it's possible to install it backwards or not but thought I'd throw that out there.

If your radiator passed a flow test I can't imagine it being clogged enough to cause overheating.

The fan is turning with force correct? Fan clutch engaging? Again not sure on these engines but could it have been put on backwards and now trying to push instead of pull air?

 

its actually boiling over, the after market gauge is stock a 140, pos, the clutch fan has engaged, but not every time, sometimes i can stop it with a hose and when i kicks in, you can tell the difference, looking at the fan it can only be installed one way, just the way the fan mounts onto the clutch part. As far as the radiator cap, its a newer cap, but not sure if its good, i'll buy a new cap and try that, thank you

 

I've never had the head off my 22r but I've seen other head gaskets that can be flipped over or reversed so you can block off water flow from making a complete circuit head to block then back again it seems like you've covered all the other bases except If you had the engine bored for bigger pistons and they went to far not very likely but sometimes a shop thats not familiar with and engine can bore to far not knowing the wall thickness of this particular engine