77 c-10 305 OVERHEATING!
 

Replaced with a better fan, new radiator hoses and thermostat and is still overheating. Is it possible it could be the water pump? Even when it gets hot enough and the thermostat opens there is almost no pressure in the upper radiator hose! Shouldn't it build pressure eventually. Also this started when I rebuilt from the heads up! Basically what I am asking is do you think more towards the water pump or the radiator which are both relatively old.

Re: 77 c-10 305 OVERHEATING!
 

Morely likely to be your pump in my opinion... A rad will still transfer heat even if it is old, but a waterpump that isn't producing pressure can cause overheating issues...

Re: 77 c-10 305 OVERHEATING!
 

If it were the pump you can tell by running the truck till the thermostat opens and watch for water movement thru the hole where the cap goes. If it doesnt move its going really slow and Could be worn out. Did you replace the Radiator cap when you did everything else? 15 PSI cap is enough for up here. Which thermostat did you use, 195? 180? 160? You can go 160 during the summer and switch it to the other during winter.

Re: 77 c-10 305 OVERHEATING!
 

Well I replaced the water pump and still its overheating! I'm thinking the gauge is is not working corrrectly because I drove it over a mile to get back home with the gauge pegged passed the red mark all the way on the H and I can still grap the upper hose for a little bit and the bottom hose is considerably cooler so its dissapating heat and there is definite pressure in the upper hose. Also I could open up the radiator cap after venting it for like 2 seconds and no steam or boiling!

Re: 77 c-10 305 OVERHEATING!
 

Is it the stock gauge on the side of the block or do you have an aftermarket one that mounts on the manifold? If its aftermarket while the engine is running crack the threads on the sensor mount to let the air trapped behind it out.
When you filled the truck did you run it until the thermo opened with the cap off and your heater on? If you didnt you might not be full and that alone can make things hot.

Re: 77 c-10 305 OVERHEATING!
 

When I installed the wrong sender for my factory gauge after my engine swap, mine would say it was overheating after running for a minute or two. It was fine after I ot the right sender. Make sure you have the right sender if you are using a factory gauge.

Maybe try installing a cheap mechanical gauge and see how it compares to the one already in there.

Slonaker

Re: 77 c-10 305 OVERHEATING!
 

Yeah I used an infrared thermometer and I am only getting about 180-190 on the thermostat housing and abou 175-180 on the hotside of the radiator and about 100-110 on the cool side so I definitely say its the gauge. Thanks for all the help!