Getting air out of cooling system, or trouble-shooting over-heating problem

[XHitman396]

DIAGNOSED (see last post)

My original thread can be found here: http://coloradok5.com/forums/showthread.php?t=264094&highlight=thermostat

After messing around with the thing a bit more, I changed the thermostat again and I still have the exact same problem. I tried getting the air out of the system, but really had no idea what I was doing. Piecing together some tips, I propped the front of the truck on jackstands and fired the truck up, I ran the truck with the radiator cap off at a little higher rpm than idle, and around 210 the thermostat seemed open as coolant came blasting out of my radiator.

The truck continued heating, unphased, until I let off the gas. I refilled the radiator and tried it again. Then I did it a couple more times with the radiator cap on. Nothing helped.

The truck just basically overheats when loaded. It will redline no problem unless I let off the gas completely for about 10 seconds, then the temp drops quickly to below 200. I load the engine to accelerate back up, and it overheats again.

By now I realized I don't know what I'm doing. So what's the deal here? It was suggested that I just drain the whole system and refill it, hoping the issue is resolved, but besides that, all I can think of is to replace the already new water pump.

Thanks for the help.

 

[bronc3buster842001]

What type of temp. gauge do you have. If it's the stock one. it could be bad.

 

[Thunder]

I read your other thread. I think Scott (4x4high) hit it on the head. It sounds like someone gave you the wrong water pump. 87 was a changeover year. Some had regular belts. Some had the serpentine system. Most bozos at the parts counter just give you whatever part the computer says. Without asking questions to make sure you are getting the right thing. They prolly gave you a reverse rotation serpentine pump.
The wrong rotation pump will usually move enough coolant to cool at idle. But soon as you put a load on it cavitates, flow stops, and heat builds rapidly.
Take the pump back and get one for a regular Vee belt system

 

[Fordum]

X2 what Thunder said, with one addition. When you take the pump back, open the new one and compare it with the one you are taking back to be sure they are different. Compare the impellers. If the look exactly the same, they are trying to sell you the wrong pump again.
Been there, done that with a water pump and inside door handles.

J.

 

[XHitman396]

4x4high (and supporters): Well played. Swapped it the other day and all systems are a go. Figured I'd let everyone know in case they were curious. So stick it in your pocket of tricks for a rainy day.

Parts store incompetence really gets on my nerves...