1990 Toyota 6 cylinder 3.0 3VZE-E Automatic Transmission, Dully Winnebago Motorhome with 51 K miles. Problem started with Overheating under any condition. We bought this 1,000 miles ago.

Now it only overheats when going uphill with the air conditioning on.
It is overheating! Boiling and steaming. It’s not just the gauge saying it’s hot.
The heater works good and the air conditioning is very cold.
Had it weighed and its not over weight.
This is what we have done so far.
Replaced rear brakes and drums.
Replaced thermostat(s) 4 times (now have a Toyota thermostat installed). All 4 thermostat’s boil tested as good.
Replaced Radiator Cap twice.
Replaced Radiator Have a Spectra Premium CU1190 Complete Radiator for Toyota Pickup http://smile.amazon.com/Spectra-Prem...eywords=cu1190

Replaced Radiator hoses.
Flushed system twice – Used pressurized system to test and refill
Removed the Fan and Fan Clutch and replaced with electric fan, installed a Flex-a-lite 674 S-blade Engine Cooling Fan with Controls http://smile.amazon.com/gp/product/B...ilpage_o02_s00
The fan is blowing (sucking) correctly.

Removed and reinstalled new Water Pump (AISIN)
New timing belt installed. http://smile.amazon.com/gp/product/B...ilpage_o01_s02

Pressure checked coolant system no leaks.
Combustible gas (blue dye) test - no gas - passed
Compression Test 170 on 5 cylinders , 155 on one cylinder
Leak down test at 100 psi (twice) - no leaks detected.

Toyota Dealership R&R Head Gaskets via the Special Service Campaign
New Plugs, New Wires
Replaced Valve seals and adjusted valves. Copy of the repair bills http://imgur.com/a/ccKwY

Dealership just did a full check on the coolant system, pressure check, computer diagnosis all were good. They did a test drive and it is still overheating with the air conditioner on and going uphill.

The dealership says I should replace the radiator, electric fan, and fan shroud with OM parts. My question is why? The truck runs great at highway speed with the air on. Runs great in stop and go traffic around town with the air on. It idles fine and the electric fan is on all the time if the air is on.
It recovers very quickly when you turn around and go downhill. It will raise in temperature slightly if going uphill with-out the air conditioning on.

Suggestions so far are fuel filter maybe is freaky and only malfunctions going uphill causing the truck to run lean and hot?

Blow out the air conditioning condenser at the car wash.

Check to make sure the airflow is going through the radiator and not around the radiator. Use insulation to fill any gaps.

Ecu can go bad, O2 sensors can lie, and several other things can cause the ecu to lean out your fuel mixture. Lean =hot.

Suggestions?
Any HELP?

 

Are you running a auxiliary transmission cooler??

The load from the transmission and the AC might just be overloading the cooling system.

added to the load is the normal load on the engine going up hill

As this happens only going up hill with the AC on and you have not had this long enough to see how it works in colder temperatures

 

This vehicle comes with a stock transmission cooler. It is a rather small Radiator that sits in front of the Engine Radiator. Mechanic's have looked at and smelled the transmission oil and they say it is fine. The truck will go in and out of 4th gear going up hill with the OD off. I have been told this is normal.

 

Sherrie, I'm going through almost the same things you are or were. When I first got my '91 Warrior, the temp gauge was generally about 2/3 of the way from cold to the mid-line marks. Then the fan blew up. In Laramie, I replaced the radiator, shroud, fan, fan clutch, and since have replaced the fan clutch again (first replacement wasn't working), the thermostat, water pump and timing belt. About to put in a Toyota thermostat as suggested in other forums. Frustrating, as the gauge will hit right up against the red line on an uphill in hot weather, and it never used to. Used an IR temperature gun to verify the gauge sending unit was OK, and it seems to be (temperature was around 240 degrees). Have you gotten any farther in your search for a solution? I have not added an auxiliary electric fan. Thanks.