I have a '92 Camry V6 wagon. Engine overheats while driving with AC on and keeps overheating after turning AC off. Replaced thermostat, water pump is working fine, and as long as i'm traveling at least 35 mph, engine temp is normal (without AC on that is). After troubleshooting & searching around, I strongly believe the hydraulic-driven fan is not running as fast as it should when engine runs hot. So where can I find: (1) a new hydraulic cooling fan filter and (2) a new cooling fan ECU? The parts stores don't carry them.

SOURCE: 1990 toyota corolla wagon 1.6 liter 5 spd. overheating

you've got a possible blockage in the head or block.

SOURCE: Overheating. Water pump appears to be good to go

the cooling system deponds on a certain amount of pressure in order to function properly, Have you tested the radiator and cap for pressure, the cap should say how many #'S it is rated at.

Verify the cap is the proper application. Most systems are a closed recovery system these days, check over flow tank & all hose's and connections, for any possible pressure leaks, visualy if you are flowing through the radiator, after the stat opens the flow should somewhat resemble a strean with current. looking through the radiator cap opening. do you have a suffecient amount of coolant to water ratio? is it loosing coolant liquid or does it just smell hot at times?

Did the thermostat get installed properly? how hot @ peak temp is it reaching, normal operating temp is around 180f to 200f.

Is the belt for water pump tight enough?

If you try to answer these questions it would be very helpfull and we can continue to address each issue as it rares it's ugly face....

It most likely flows from bottom to top. we will also want to verify the gauge or light is functioning proper, and not giving a false reading, when you jumped the fan did you verify it was spinning in the proper direction.