Thanks to everyone that has helped me in the past with my I6's, and once again, I'm in need of help again. Since it's been getting quite warm here in Central MO, i've decided to run the A/C some and noticed that my engine decides to overheat when idling, but only if the fan selector switch is not in LOW. It's confusing, but whether I run it on Max A/C or Normal A/C, it will overheat whenever I have the fan selector switch any higher than low. I replaced the rad. cap and thermostat last october. And regardless of it overheating, it BLOWS COLD! That's why I love Ford for the A/C, Brrrrr! I also drained and flush, and reflushed and changed upper and lower radiator hose in MArch of last year. And I will say that last year it did the same thing but I hardly ever drove the truck but all the air in the system has been vented and I'm confused. If anybody has a good idea where to start, let me know, cuz I'm all ????????'s here.

Thanks Again,
Timbersteel

 

When you replaced the coolant, how did you mix it? Is it 50 to 50. 50%coolant to 50% distilled water. If you put in straight coolant without mixing ,the coolant won't cool your moter very well. Believe it or not the coolant works better when its diluted with distilled water. Useing the ac and on High does put a drag on the motor expecially at idil. There is no airflow across the motor. Did you check to see if you fan is spinning. Do you have a fan clutch? Maybe the fan clutch is not being told by the computer to turn the fan when the motor is hot. This might have nothing to do with the ac but the drag on the motor when you use ac.
Just a thought. Take it or throw it out the window

 

I think I'm going to try and replace the fan clutch, considering the truck has 96K miles on it. I have to work all this weekend, so I will get back and let you know how it went. Thanks again for the info.

 

The fan clutch is a good thing to start with. The computer has nothing to do with that, it's just supposed to turn on when it gets hot. Is your fan shroud intact? If not it can cause problems. I've had a couple of problems with overheating at idle caused by a water pump impeller that was eaten away by rust.

 

how does the fan turn on when it gets hot? something has to tell it to turn on. Could it be a thermister that turns the fan on? I dont know.
Good Luck

 

Ok-- A couple of things to consider. The fan clutch is mechanical and a function of the fan clutch hub and not the computer, that is unless it is an electric fan. The purpose of the fan clutch is to disengage the fan at road speed and to let the fan rotate at Idle. If the clutch is totally bad it might not let the fan run at idle , but the engine would probably overheat even without the AC. Secondly the AC on low or high has no bearing on the engine as the compressor only has two speeds -ON or OFF. It is possible that on low blower speed the temp in the cab will cycle more often and allow the compressor to shut off for a period of time or the refrigerant doesn't pickup as much heat on low blower and therefore the condenser in front of the radiator is cooler allowing the incoming air to the radiator to be slightly cooler.. Thirdly the timing has something to do with overheating , if I remember too retarded will cause hot running. The radiator could be clogged even if you ran flush through it, have it cleaned by a radiator shop. How about the water pump belt , is it glazed and slipping? Having said all that , I have a 1990 and have replaced the cooling system parts and added an aluminum 3 row radiator when I installed AC in the truck a few years back and at idle it has always run hot with the AC on but always returns to freeze when you start to drive, it is when it doesn't come back to normal that I would worry. I had considered an auxiliary electric fan but never got around to it. The fan clutch is operated by a bimetallic coil spring on the front of the clutch and by slipping (it is oil filled and works like an auto trans torque converter) at high engine speeds. Here is an explanation, the ford is a thermal type.

To minimize the power loss, clutch-operated mechanical fans have been installed for decades. Most fan clutches typically engage at about 170 degrees air temperature (185 degrees engine temperature), run at 60 percent to 80 percent of engine speed, and will generally reduce the engine temperature about 20 degrees.

There are two types offered, and both operate on the fluid drive theory. One's a thermal type, which is typically what auto manufacturers have used, and the other is a low-cost and low-performance style called a non-thermal. The better thermal fan clutches varies the fan speed with temperature of the air behind the radiator. An identifying feature of a thermal fan clutch is the bi-metal thermostatic coil located at the front of the clutch. This coil senses the under-hood heat and activates the clutch accordingly. The operation (when engaged) provides maximum cooling, while the disengaged operation provides fuel savings and noise reduction.

Non-thermal clutches (also called centrifugal) are a low-cost replacement part. Although comparatively inexpensive, non-thermal clutches are always engaged, providing less fuel and power savings than a thermal-style fan clutch.

stractor

 

throw some water wetter in it too!