My daughter has a 75 f100 with a 1980 ford 302 motor. Its been with us for about 10 months. We have not had it for one summer yet. We recently had the heads completely rebuilt and just got the truck back two days ago. She decided to go to the beach in maine today. Before she left I checked the radiator and it had plenty of coolant. I told her to watch the engine temp guage. It stayed between H and C the entire way up. A two hour drive. She stayed all day and just decided to come home an hour ago. She just called saying the guage was fine until she hit a traffic jam. The temperature guage started to go up. Sne called me and I told her to turn on the heat. It is currently 88 degrees at 830 pm. Anyone have any ideas other than the extreme heat?

 

Does it have a fan clutch? Fan shroud?

 

it does have a shroud. I am not sure of the clutch. I will see when she gets home. She called just now and said traffic is moving and the temp is dropping. This is good news but not the answer.

 

Ck fan operation and air flow . A shroud is a must . Mine has a solid fan and factory shroud ,no issues . It was in the high 90's today .

 

. It has a shroud and a solid fan. The engine is a 80 but the fan seems to sit half in and half out of the shroud. It seems correct. Should I flush the radiator? It ran fine after the traffic stopped. The truck never overheated. The temp gauge just went up.

 

A flush would be ok , but will not likley solve your issue . If the radiator were plugged internally it would overheat at speed and high load . Sounds more like an airflow issue , or , an over cautious driver . Try a good quality mechanical temp gauge or use an IR gun to find out how warm it actually is getting . It may be nothing to worry about .

 

I will have her watch the truck temperature after I flush the system. You may be right on the over cautious driver. Thanks

 

When you flush it , replace the T stat .Just for good measure . Be sure to use a good quality one though . Motorcraft , or another good quality one . Most flush chemical instructions ( that really work ) require you to remove the T stat anyway .