I've got an '84 F-150 with the motor and cooling system from an '89 which I carburated about 8 years ago. Been running fantastic till about 2 weeks ago. It started running hot and the heat was blowing cold air. So, I replaced the heater core, heater hoses, by-pass hose and thermostat.

While I was changing them I noticed that the radiator was really gunky and the heater hose passages where stopped up. Cleaned it up, put it all back together, but the same problem exists, although now I do have heat. I assume the passages being opened solved that.

However, it still over heated. So, I got a new rad, hoses, and flushed the system again. Still over heating. Just happened to notice that both hoses are collapsed flat when engine speed picks up. Now I'm assuming that they were collapsing in the first place. But, it's never done that before. Had a suggestion to put a spring in the bottom hose, but it's never had on before. Thermostat is new. Never seen both top and bottom hoses collapse though. Any ideas?

 

you may have installed the Tstat backwards. this is a common mistake. its also possible that the cooling system needs burped. you might also replace the radiator cap.

 

Burped? Never burbed a cooling system before. It's pushing a lot of water out of the radiator when the cap is off though. And when the engine is shut off the hoses slowly collapse until all the water is sucked from the overflow.

 

Probably a combination of things. Radiator is still plugged, t-stat in backwards, bad radiator cap plus too much air in the system. The hose is collapsing due to pressure change and not being able to vent. The water pump is driving the water to fill air voids, in the block or radiator, which causes temp variations, and the system has nothing to fill the hoses with so they collapse. There should to be a spring in the bottom hose. Have the radiator proffessionally cleaned by a radiator shop, or replace it. If it's in rough shape I would just replace it.

 

The radiator is new. Thermostat is incorrectly. It's never had a spring in the bottom hose. I can't find one with a spring in it. My water pump is warranteed and it's sqeaking a bit, so I'm gonna replace it. The only thing is not new, or won't be soon is the heater core which I took out and flushed. I'm gonna make sure I drill a small hole in the t'stat flang this time.

 

"It's pushing a lot of water out of the radiator when the cap is off though."

That's indicative of air in the system. You've got to purge that out to let it function properly. Drilling a hole in the thermostat will help, but it will also delay the warming up of the engine.

 

when it cools and the coolant contracts it will form a vacuum in the cooling system. There is a valve on the bottom of the cap that shoud open when it has neg pressure, allowing the coolant to be sucked from the overfflow. Sometimes they get stuck, just open it manually to unstick it and it should quit sucking the hoses shut and help get the air purged from the system.