94 Explorer Overheating w/ AC on

[StillKicken]

I have a 1994 Explorer with a 4.0 V6. It has 270k miles. New engine at 180k miles. Am sure water pump is fine as it only overheats when I am doing slow city driving with AC on, or if I'm idling with AC on. No AC...no worries. Has new 2 row radiater. Think that fan clutch is ok as I did the test where when engine is cold spins freely, when hot it has some tension behind it. The fan does have like 6 - 7 cracks in it. I have rechrged the AC with r134A also. Thanks for the help in advance as this is driving me CRAZY!!!

 

[shamaal]

Most likely culprit is thermostat, other possibilities are cracked fan or cooling system blockage.

As you've surmised you should be able to idle without overheating.

 

[StillKicken]

Don't believe its the thermostat as it only does this when running the AC. Was going to replace fan and clutch with a flex fan. Wanted to put on an electric fan, but not enough room for a high output electric fan. Think the flex fan will help?

 

[Darrman]

I had the same problem the other day, replaced the fan clutch and has worked perfect since then. If your fan is cracked, that should not affect the cooling, but it will wobble out the water pump/fan clutch bearings if it gets bad enough.
A good flush and new t-stat never hurts, the rad may have some gunk in it, mine sure did.

 

[StillKicken]

Thanks Darrman. Well, I had flushed out the system before I put in the new radiater. I had a one row in their before and put in a 2 row radiater. Thought that would fix it. I think I am going to put on the flex fan and pray.

 

[shamaal]

The second time my engine overheated, there was boiling water in my overflow tank. The cause was a cracked fan, it would spin and everything just not with enough torque to be effective.
When working with OEM parts there is more than sufficient heat rejection capacity in the system; occasionally there are complaints in this forum that the engines are too cool.
You are right something is wrong. It will show up at idle, as this is the worst time for heat rejection. While there is heat in the A/C condensor pulled past the radiator, on a properly working system there is more than enough heat sucked out of the radiator to keep the engine at operating temperature.
Changing you t-sat whenever overheating occurs is still a good idea although I think the most likely problem now is the fan.
Let us now how it works

 

[StillKicken]

Thanks very much for y'alls help. Have to order a special spacer from Flex-A-Lite so may take a couple weeks for it to come in. But will be sure to post outcome. Thanks again!!

 

[StillKicken]

Well, replaced the stock fan with a flex fan a week and a half ago.
Worked fine for about 2-3 days....now its doing the same thing again. When sitting at a light it starts to run hot. AHHH!!!! I work in a nice HOT plant, and the temps are soaring to the 100 degree mark. Thats probably not helping matters much. Guess I'll have to suck it up, haul tail home with no ac and then jump right into the pool when I get home!

 

[shamaal]

There has been a rash of these problems where the most common culprits are changed, but there's still a problem

Especially puzzling is the work fine for 2-3 days part.

On my 91, the temp moves up 1/8 to 1/4 of the gauge when stopped in this weather, then drops down again when underway. When you say you are overheating, are we talking about at the top end of the gauge?

 

[budwich]

I don't think your fan is suppose to spin "freely" ever. There is supposed to be some resistance.... quote "Spin the fan. A light resistance should be felt. If there is no resistance or very high resistance, replace the fan clutch".

 

[StillKicken]

I don't think your fan is suppose to spin "freely" ever. There is supposed to be some resistance.... quote "Spin the fan. A light resistance should be felt. If there is no resistance or very high resistance, replace the fan clutch".

I replaced the stock fan/fan clutch with a flex fan. The fan works like a normal fan at idle speeds, but flexes to reduce drag at higher speeds/rpm. This new fan does not spin freely at all.
With no AC, the temp is fine. When I run AC, it gets HOT, needle ALL the way to the red. Well, as close as I was willing to let it get.
The first couple of days after I put the fan on, I ran AC no problem. Then it went back to same ol problem.
Radiater is a brand new 2 row with lifetime warrenty. Thermostat is not too old. Water pump is a couple years old, but do not see anything leaking out the weep hole.
Condenser have too much gunk in it maybe that keeps it from breathing and getting too hot?
Mind boggling.

 

[budwich]

Cheap test.... pull your thermostat. It should run cool / cold with or without your A/C running. If your temperature still climbs especially any way close to red, then you know you are chasing a problem with circulation.