Car is completely stock 64 1/2 with a 260. It will drive all day in town w/o overheating. I noticed that the top hose is empty which means that it is not getting to 180 degrees to open thermostat, right? Anyway, temp rises rapidly after about 15 min at highway speed. all hoses are new, water pump new, radiator new, flushed multiple times, thermostat new. timing set at 8 deg. What to do next? Is is possible the new rad is defective in some way?

 

It could be your bottom hose getting sucked closed during highway rpms.. Squeeze it and see if its a little soft. They came stock with a spring inside it that kept it from happening. Thats usually what the problem is with these old SBF's. And fill your radiator to within an inch of the top of the filler neck. You should have water in the top hose.

 

hose is new and I have never seen it collapsed. Fluid is full.

 

I'm guessing its the radiator it can't be the fan at highway speeds the fan does nothing.You could take the radiator out take it to a shop that will clean and rebuild it for you or use it as a reason to get a alum one.Is the radiator cap holding pressure? Or thermostat in upside is all i can think of.

 

Thermostat stuck open?

 

And you probably never will see the hose collapsed, it is only going to do this under certain conditions.

The hose will only collapse:

a. When the system is not under any real pressure.

In a properly performing cooling system, expansion from heat, once the car is warm, will prevent the hose from collapsing. A leak or a defective rad cap preventing the building of pressure would need to be an issue.

b. When the engine is at temp (thermostat fully open) and SPEED, the water pump can suck the bottom hose shut if it does not have a spring.

So, it might be a collapsing hose AND a bad radiator cap

Or, the pump you put on MIGHT be a reverse rotation pump? (is it possible to do this on a Ford?) IDK

Or, the thermostat you put in is defective, if you changed the thermostat because of this same issue, it probably ain't your problem.

Or, worst case, a compression leak is robbing your cooling system of it's efficiency and expelling your coolant.

 

rad is brand new, has overheated with two new thermostats(installed correctly), Hose is new, but doesn't have a spring. I even went as far as to install new head gaskets this wkend. Still, temp rises steady on highway. As soon as I get off and return to slower intown speed temp comes down.

 

Hello there. I just read your story about how all is new and you only overheat on the highway? The upper rad hose being empty should tell you your not full if you checked it when it was cold. If any doubt change the rad cap because if its not right your boiling point will not be right. These cars are horrible for overheating. But your problem is opposite of everyone else. Sounds like your cooling system is not under pressure so your boiling point is not high enough. Circulation and fan speed dont mean crap at high way speed. Check your rpm and what gear your in. This could make your car easily overheat if its working too hard.

 

There's where I'm putting my money. Hose is collapsing when at speed, unless the hose has an internal wire.

 

Lower hose makes sense to me too