Radiator overflowing

[67 ford f100s rule]

Nadine my 70 Lwb has a little problem. when i start her and let her run the radiator overflows. Does anyone know what could cause this?

[Dragon]

All the time? Do you fill it up every time it does this? My water never shows above the core when the engine is cold. If I fill it cold to the top it pukes it out.

[67 ford f100s rule]

All the time? Do you fill it up every time it does this? My water never shows above the core when the engine is cold. If I fill it cold to the top it pukes it out.

yeah all the time. I fill it up to the top cold. Do you know how much the 302 radiator should hold? According to the previous owner it wants to overheat.

[Dragon]

Never fill it to the top it will always through it away about an inch above the core. It over heats for 3 reasons, bad thermostat, bad water pump or damaged/clogged radiator.

[67 ford f100s rule]

ok I will remember that nexrt time i put coolant in it. The top hose gets warm but the bottom does not change temperature. I have heat so I am pretty sure that the water pump is good. The thermostat was replaced not too long ago.

[JMcTurnan]

Thermostat doesn't always mean that it still works cause you just replaced it. I have had 1 or 2 get stuck after only 1 month of installing them.

[67 ford f100s rule]

Thermostat doesn't always mean that it still works cause you just replaced it. I have had 1 or 2 get stuck after only 1 month of installing them.

good point but it seems like the coolant is entering the radiator but its not leaving it. I think the clogged radiator is the most likely problem. I am not sure how to text it though.

[Dragon]

The radiator core would get real hot if the core was clogged. The water going back to the engine in the winter can be real cold. I had my sensor for my electric fan down by the outlet and this winter my fan would not turn on. So I moved it by the inlet and blocked half my radiator off so the engine was getting warm water not cold. Works great and I am getting better mileage now that my engine is keeping the water warm.

What gets me is how big the truck radiator is compared to say a Galaxy or a Mustang. Yet they had the same engine. In the winter I never had to cover my 390 Mustang radiator even in high country Colorado but my 390 truck I do have to, to keep the engine from cooling too much.

To test it cover the radiator with cardboard on have the radiator and see if the outlet is getting hotter.

[ezernut9mm]

the best way for us shade trees to see if the radiator is clogged is to drain it, un hook the lower hose, put a garden hose in the top and turn it on. if it comes out the top way faster than the bottom then it is clogged.

[BobbyFord]

Pressure test the radiator cap.

[QC]

It's probably just over-full. It should be a couple of inches below the filler when its cold. Water expands as it heats up.

[cdeal28078]

Was the engine rebuilt just before you got it? Head gaskets get put on backwards on 302's and 351W's pretty easily
clint