I have a 1993 ES. Automatic. Overheating pretty badly. I have replaced the radiator, main hoses, caps, and thermostat. The only thing left is the water pump! Does anyone know if there is something that I am overlooking???

 

Nope, That leaves the Pump. Are you losing coolant anywhere?

 

Another vote for the WP.

 

Did you make sure you burped the coolant system? Normally when you drain the coolant and refill it( or if you lose alot of coolant at all) the system will develop air pockets in it. You need to let the car run from cold to hot with the cap off(normally the highest accessible point in the system) to allow these air bubbles to work themselves out otherwise the car will overheat. The water pump cannot push these pockets of air through the system thus you end up with a car that is being overheated because coolant is not being circulated.

Normally if it is the water pump it will be easy to diagnose, most cars have weep holes on the pump that will start leaking and the shaft of the pump should have no play in it. If it does you have a bad pump.

I would also hook a pressure tester up to it to see if the system is holding pressure, this should also expose any small leaks you might be missing.

 

When does it overheat? If it occurs when the car is idling or moving slowly in traffic, check out the operation of the hydraulic cooling fan.

The operating speed of the fan is controlled by an electronic control module located under the glove box. This module monitors the operating temperature of the engine and adjusts the fan speed accordingly. There is a wiring harness that attaches to the power steering pump that carries this signal from the module to the pump. If this harness is damaged or becomes disconnected in some way, the fan will not turn fast enough. The car then overheats.

If you are driving at a good rate of speed, the air movement across the radiator will keep the engine cool. If you're not moving very fast, an increasing fan speed is critical to keeping the coolant temperature down.

 

I have had overheating issues from hell with my 93...I replaced the waterpump, thermostat, radiator, caps jumped the pins at the diagnostic plug to run the fan on high, blead the air out all to no avail... turned out the head gaskets were bad and one thing I overlooked and that was a continuous small stream of bubbles kept coming out of the cap... combustion excaping into the cooling system... unfortunatly for me the block was NFG as it was rusted out under the compression ring of the head gasket the pits were 1/8 inch deep... installed jdm engine with all the new parts problem solved ... I hope you dont have this problem but check for the stream of bubbles...

 

Ok so I've checked most of thread about "Overheating Issue" and this seems to be a possible problem with my 93 ES300. Only deference is my car overheats and coolant will start bubbling in a reservor ONLY when A/C is on. Otherwise stop and go in a city, hwy driving with no overheating issue AT ALL. Fan is operating when engine is hot/warm but speed does not change with either A/C is on or off. So I don't know if it is tuning "fast enough" or this is normal by just looking at it.
Question is: Does this "Electric Control Module" affect with A/C switch?
Is anything else that I should check?
Any suggestion will be appliciated.
Thanks.

 

After reading a manual, it looks like Cooling Fan ECU has something to do with it. Also does anyone know where is "solenoid valve" for cooling system is located? Looks like there is a "control valve" on Hydraulic Pump/PS Pump but it does not looks like connected to Cooling Fan ECU.
Thanks

 

Yes, it is the control valve on the PS pump.

 

This is what my 1992 ES300 does (continuous small stream of bubbles) and I have used a chemical color change tester to check the radiator for presence of exhaust gases and found no gases present.
I did replace the radiator decause it was clogged and it still overheats when I come to a stop then cools as I gain speed again.
I'm thinking cooling fan solenoid.
Does anyone know the test to verify this?