Hi guys, I put a 85 300 in my 56 pickup. Now it seems to be overheating. Here's what's happening. The upper hose is hot as can be, the lower hose is cold. The engine was in a 85 F150 I bought it off the original owner. It was very rusty and had no brakes but I did run it in the body a long time and no overheating issues. The coolant in the truck was very rusty- not green but brown. I replaced the water pump because the pipe nipple that goes to the heater house was rusted badly. The truck had a newer aluminum radiator in it, which I couldn't use due to the sizing. I bought a new (China) radiator for a Chevy V-8 in a 53-56 Ford truck because I needed the lower hose on the passenger side for the 300. After getting the engine running in the 56, I removed the thermostat and ran it with straight water in it, drained, refilled drove it around some- I filled, drove, and drained probably 3 times. Then filled it again with clean water and heavy duty flush. Ran it with that for a couple days. Then drained and refilled again with water. Then put in new thermostat and 50/50 antifreeze and water. The radiator has a 16lb cap which I have been using. It got hot and acted like the thermostat was stuck so I changed it with another new one. But as I said the lower radiator hose is cool. Any ideas? I am confused. Thanks for your help, advice. Greg.

 

Hi Greg,
Are you 100% sure you're putting the thermostat in the right direction? I've made the mistake of putting them in backwards before.
There's one brand in particular, Moto Rad that is notorious for this. Main reason... They put their name on the side of the thermostat with the word "Moto" toward the radiator and "Rad" toward the motor. So, they look like they're installation instructions when they're just a logo, but if you install it that way, it's backwards.

 

How cold is the cold bottom hose? How long are you letting it run before you shut it down?

If it's near ambient temperature and the engine is overheating then there's something preventing the system from flowing like it should. It could be the radiator or it could not be. If the coolant is moving very slowly then a properly functioning radiator with a good fan will leave it not that much warmer than ambient temperature when it leaves the radiator.


I'm betting there's a nice thick layer of rust and junk somewhere in the system that was knocked loose when you flushed the system but wasn't suspended in the coolant (it was just floating around from turbulence) so a substantial amount of it didn't get removed when you flushed the system.

 

Thanks Bronco, I have the spring toward the engine. which I believe is correct at least as it shows in a Chilton manual I have. I am worried that maybe the water pump is bad or maybe the impeller is made to turn the other way?? I know the newer 300's use a serpendine belt, but I bought the pump for a 85 and am using the original V- belt setup and fan clutch from the 85. I would doubt that the impeller would come off as is seems I would hear it or the shaft would start to come out? I'm going to go mess with it again today. Thanks again, Greg.

 

That may be. I'm going to check it out a little better today. Thanks

 

I've seen impellers come loose on the shaft, especially the stamped kind which are inferior to the early cast ones. Maybe pull off the radiator hose coming from the pump to see if coolant is flowing with the engine running? If not - spun impeller.

Needless to say, do this with a cold engine.

 

Well yesterday I took everything apart. There was some rust particles/crud in the bottom of the rad and the water pump was ok. I fluhed everything out with the garden hose and put back together. I drove it over to my buddies house and it was fine. He had a underdash temp gauge I got from him and came back home and installed it. It is fine. I feel a little stupid as I don't think I let it run long enough after I changed the thermostat the 2nd time. I do think the 1st tstat was stuck closed. When that one was in the upper rad hose was very hot and hard as a honeymoon co*k! Now it is quite warm but not as hot and no where near as hard. The temp sensor is towards the rear of the engine and it shows 180-190. Thanks for your guys help, Greg.