93 Ex Won't Stay Cool

[msmith65]

I've been having cooling problems with my '93 Explorer for several years. It can't tolerate idling very long in the summer.

I've replaced, in order: fan (10-blade) and clutch (Motorcraft); thermostat (180); radiator (2-inch core); and water pump (heavy duty).

And I still can't get it to idle with AC without overheating. It seems to have gotten worse this season, overheating at low speeds or when climbing hills.

Now I'm wondering if I put too thick a radiator on it? This was suggested by someone at an air-conditioning forum.

The AC hasn't been able to keep up, either, especially at idle. (FYI I installed a heater control valve a couple of years ago, to no benefit.)

Any ideas would be greatly appreciated.

 

[safn1949]

When running with the radiator cap off,does it bubble or spew coolant? I suspect a head gasket problem,letting combustion gasses into the coolant.But if it doesn't do any of the above there is a fool proof test that can be done in 10 minutes or so to see if the head gasket is leaking.Has to be done by a shop.

I also don't see where you have replaced the hoses,if they collapse it will hinder coolant flow and overheat also.They also can collapse internally due to age.I have found that most overheating problems are caused by the radiator,but you replaced it.Using a radiator with more cores shouldn't cause a problem.

Make sure your AC condenser isn't plugged with crap reducing airflow to the radiator.

 

[surf]

Are you losing fluid? Have you changed your cap?

 

[msmith65]

Thanks for the questions:

No coolant loss. Clean behind the condenser. Have not replaced the cap. How would a faulty cap affect things?

FYI when I arrived home recently the temp gauge was reading way into the high zone, and when I pulled the hood to help it cool, the cap let a bunch of coolant into the tank.

One thing I have not successfully done is warm it up and looked at the radiator flow with the cap off. It seems to take forever to warm up in the driveway and then coolant bubbles over and makes a mess.

 

[surf]

The cap raises the boiling point of the coolant by maintaining pressure in the system. A cap that leaks will let the system boil over into the reservoir and can result in a fluctuating temp gauge. Checking the flow with the cap off is a good idea. Sometimes a new thermostat will be defective.

 

[msmith65]

With the engine warm, I should be able to see the coolant moving in the filler neck, yes?

I took the cap off and ran the engine until it warmed up. After a few minutes some coolant belched out, then it stabilized.

But even with the thermostat cover reading 204 degrees (infrared thermometer), I couldn't see anything moving in the filler neck.

I squeezed the upper hose and could see some change in level, kind of a wave. But no flow.

(BTW, before I did this test, I replaced the cap -- no effect on overheating. During the test the upper hose peaked about 204 degrees, the bottom 160. The radiator is fairly new -- two or three years, and the coolant looks clean. I have replaced the thermostat once, maybe two years ago.)

 

[Doomie17]

flush the system you might have crud running around in there.

 

[safn1949]

I would go ahead and replace the thermostat with a good one not a $4 special.Flush the system with one of the super flushes.Just for piece of mind I would have a shop do the head gasket check to see if combustion gasses are in the coolant.When the stat opens you should see flow,it will open and close some to keep the temp steady so the flow will change.

Do you have heat? Air in the system will stop the flow and it will overheat also.Let it run in the driveway and turn the heater on and let it warm up.Are the heater hoses hot? Top hose hot?

 

[msmith65]

safn1949, the heater works fine.

Because I don't have time for controlled experiments, I pulled the radiator and flushed it; checked the hoses for obstructions, and replaced the thermostat in one operation.

The temp reading at the thermostat housing now peaks at 190. I drove around 20 minutes and the temp gauge never got above the O in NORMAL.

Success! I bet it was the thermostat. There was some brown water coming out of the radiator with the flush, but no chunks or flakes.

Thank you for your suggestions, gentlemen. I'm declaring victory and having a beer.

 

[safn1949]

safn1949, the heater works fine.

Because I don't have time for controlled experiments, I pulled the radiator and flushed it; checked the hoses for obstructions, and replaced the thermostat in one operation.

The temp reading at the thermostat housing now peaks at 190. I drove around 20 minutes and the temp gauge never got above the O in NORMAL.

Success! I bet it was the thermostat. There was some brown water coming out of the radiator with the flush, but no chunks or flakes.

Thank you for your suggestions, gentlemen. I'm declaring victory and having a beer.

Glad you got it handled.

 

[msmith65]

One follow-up note: While flushing the radiator off the car, I filled it with water then let the hose run, flowing through top-bottom while I watched the filler neck.

I don't know if all Explorer radiators are like this, but I couldn't see any evidence of flow through the filler neck -- just water sitting there. I think it goes too deep into the radiator for the flow to be visible in it.