My 1989 truck is overheating. Previously it rarely went past halfway on the temp gauge, now it keeps going, maybe a bit slower. In cool weather (<80) it will run very close to the red (about 3/4) on the freeway and and around town it gets just shy but still pukes. The radiator looks clean, I pulled it out and sprayed it, there was very little trash to block the airflow. I replaced the water pump and thermostat, the hoses appear fine. I pulled the water pump and the impeller seems firmly attached, the belt seems sufficiently tight. No loss of coolant except what boils out. I have had the truck for several years and this started 5 or so months ago with the gauge getting to 5/8 or so. With the hot weather it is now out of control. The gauge never got above 5/8 before and only briefly and would return to half our just under. I can't find a damn thing wrong.
^that. I've seen several older Toyota pickups lose the fan clutch and require a rebuild or at least a refill of the fluid inside. Also old radiators do get clogged with time. I think more prone if you don't use Toyota red coolant (?). Anyways, try having the inside of the core flushed out, the passages may just be clogged up.
(i am currently wiring up the new electric fans on my new aluminum radiatir on my overheating engine. I have noticed a lot of these threads pop up in the past couple weeks, so you are not alone!)
I searched "overheating" and only found 5 that didn't seem to address my problem. The radiator looks clean inside and water from a hose passed right through.
Have you got the correct thermostat? Did you "burp" any air bubbles out of the system when you changed the water pump? I've found over time if you go back to when you first noticed the problem did you do any work on the engine? This might be a good place to start. The 20R has a bleed screw on the drivers side of the block. This helps with getting any air out of the system(not sure about 22R).
The fan clutch is pretty loose, I'll fix that but I don't see how that is making it run hot on the freeway. I changed the water pump about 3 years ago and had no problems until a few months ago. No loss of coolant until it overheated. I suppose an air bubble could have been trapped when I drained the system to replace the thermostat but I've notice no change in the symptoms. I put a garden hose to the radiator and the water flowed through so I don't think there is any restriction in the radiator. The only thing left besides the fan clutch is the lower radiator hose and that seems fine. I don't mind replacing parts but I'd like to have some confidence that I'm actually fixing the problem instead of throwing money away.
have you checked valve spacing? if the valves are off, hot exhaust gasses not going down the exhaust can heat your engine up.
Just for fun , remove the thermostat. Put everything back together and run the engine until it gets to operating temperature. Replace the thermostat with one rated for 165 degrees. The fact this started when you changed the thermostat could mean you just got a bad thermostat. Running with no thermo should bleed any air out of the block. Install the replacement thermostat draining out as little coolant as possible. Be sure to turn your heater on when you run the engine. This will take care of any air in the heater core.
It started before I changed the thermostat. I got silicone to refill the fan clutch, if that doesn't work I'll try taking the thermostat out. I got one of those fail safe thermostats that locks open, it may be locked open now.
If the coolant is boiling out that usually suggests the thermostat is not opening or not opening 100%. There is no such thing as a "fail safe" thermostat. Try installing a plain generic thermo. Even new thermostats can be defective.
I tightened up the fan clutch and I don't overheat anymore but I still don't think it's right. I'll probably get another thermostat and see how that goes. I think the current one may be stuck open and on a hot day the other week the temperature got pretty high when I had the AC on. The fan is definitely too tight but the truck isn't overheating so I'm going to leave it until I think the rest of the cooling system is 100%.
