On my '79 F-150 with a 302, I get an intermittent overheating problem from different ranges of outside temperatures. The thermostat has been replaced, the coolant is good, and the oil has been recently changed. Any ideas what would cause this to happen? I'm tired of running the heater every now and then when it's 70 degrees out.
Thanks for any help
WrenchHead

1979 F-150 Custom. 302 V-8 4-spd 2WD. 122,875 Miles

 

It took me a newer radiator from the wrecking yard to cure that problem. It was corroded up inside and plugged up passages. Hard to see anything wrong, but that cured it. I had already done the flushes, new water pump, thermostat, etc.
Mark



>On my '79 F-150 with a 302, I get an intermittent
>overheating problem from different ranges of outside
>temperatures. The thermostat has been replaced, the coolant
>is good, and the oil has been recently changed. Any ideas
>what would cause this to happen? I'm tired of running the
>heater every now and then when it's 70 degrees out.
>Thanks for any help
>WrenchHead
>
>1979 F-150 Custom. 302 V-8 4-spd 2WD. 122,875 Miles

 

I'd check two easy things before removing your radiator. First, replace you radiator cap. It's not just a cap, it's an important part of the system in maintaining correct pressure, which means correct cooling.

Secondly, I'd test the thermostat. About 6 years ago I replaced the thermostat in my Corolla with a brand new one. Well, the new one was no good. You can test yours on the stove top in hot water.

If you had an electric fan, I'd tell you to also check the relay. Oh well.

Intermittant over-heating is always caused by bad circulation of some type. Most often, a malfunctioning thermostat. It could also be that your block is dirty. Over the years, antifreeze puts silica sand in your block. Have you flushed your block lately?? I don't mean through the radiator, I mean through the block drain plug.

 

Might want to check the fan clutch to?

 

 

Check the sender unit and wires to make sure you get an accurate reading.


Bear

 

Wrench,
It's not your thermostat.
It's not your automatic tranny; you've got a 4speed.
Is it your fan. There is no fan clutch on your truck.
I'm afraid it's your radiator. I have often said the best investment you can make in your truck after changing the oil is a strong radiator. Get it boiled and brushed for about $40 and you'll be good to go.
My Way is the Highway,
KingFisher