2.3 getting hot while ac is running.

[Shotrod69]

1996 2.3 5 speed.
While sitting idling or driving down the road at 70-80, when running the ac the truck gets really hot.
It’s never “overheated”, but that’s also because I shut the ac off before it does. Normal coolant temp is in the bottom 1/3 of the normal operating part of the gauge. A couple of times when I wasn’t paying attention it got to the top hash mark before I shut off the ac and pulled the clutch in and throttling the truck up. (Take away the load and keep water/air flow still happening.)
I had a 93 with the same set up I put a v6 radiator into while living in Florida. (It was all the junk yard had that would match up hose locations. The 3 other 2.3 radiators I had to return because they sprung leaks.) It never overheated and would often take a long while to warm up.
My question is this: What could be causing this?
I’m not saying the fan clutch isn’t bad, but wouldn’t the issue go away at 70-80?
Thermostat has already been replaced.
Radiator could be plugged but I doubt it. I ran water and dishwasher soap through it first. Then rad some type of radiator cleaner through it. Then soap water, then flushed it for about an hour with a garden hose hooked up to upper rad hose.
I don’t see how it could be the water pump if normal driving doesn’t cause issues.

 

[franklin2]

Next time it gets warm to hot, pull over and turn it off, and go out and try to spin the fan. It should be locked up. If you can spin it, I would get a new clutch for it.

 

[Shotrod69]

Next time it gets warm to hot, pull over and turn it off, and go out and try to spin the fan. It should be locked up. If you can spin it, I would get a new clutch for it.

I’ll do that. However, even if the fan clutch is bad, shouldn’t it not be an issue if I’m doing 70 or 80 miles an hour?

 

[sgtsandman]

It could be that the impellor on the water pump is not properly seated on the pump shaft or that the impellor has erroded away and is not providing enough flow to compesate for when the A/C is on or when you are traveling at high speed, but is otherwise fine.

On the speed side of things, since you are shoving a brick shaped object through the air, the engine is working hard against the aerodynamic drag. So, it's genersring more heat.

The same goes with when the A/C is on. The system is generating quite a bit of heat that is also run ing through the radiator and over the engine, warming things up.

So, if the clutch fan checks out, I would look at the water pump imprellor.

On the clutch fan, if it is functioning correctly, it should be stiff when cold. Free spinning after a couple of minutes of engine operation. And stiff after the engine heats up to operating temperature.

 

[pentode]

I would definitely confirm the radiator is healthy before I dug too deep. I've seen a few cases like yours that were caused by stop-leak and/or other junk in rad. My rule of thumb is that a garden hose on full blast should flow through the rad without overflowing. If it's crud in the radiator I find a good back flush with the hose often helps. Stop leak, not so much.

Edit: I just reread what you wrote. You said "it could be plugged but you doubt it" and also that you ran a hose through it... Did you check to see how well it was flowing?

 

[franklin2]

I’ll do that. However, even if the fan clutch is bad, shouldn’t it not be an issue if I’m doing 70 or 80 miles an hour?

Radiator could be partially plugged. Here is a test for that;

Drain the coolant, pull the lower radiator hose off.

Take the radiator cap off.

You may need a helper, hold the palm of your hand over the lower radiator outlet to block it off.

Then fill the radiator up to the top with water.

Then quickly pull your hand off the lower radiator outlet.

The water should come out of the lower radiator outlet full flow, quickly draining the radiator. If it comes out only partially filling the lower outlet, and is gulping and struggling some, then the radiator is partially clogged.