I have a 1989 F-150. I just flushed the radiator and put one jug of 50 antifreeze 50 water back into the radiator. I let it idle for 20 min and the whole time I had heat. Then I got in a drove it about 10 miles and the heat went away. I turned the heater off for about 5 min turned it back on and had heat agian. Is there something I am doing wrong or does it just need more antifreeze?

 

You need more coolant in the system,check your owners manual to find out the coolant system capacity.

 

You need to let the air out also, when you don't have heat you have air in the system, Leave the cap off for a while keep a hose handy and every time the water goes down and circulates through the engine add water to top it off.

 

Ok thanks that is what I was thinking but I wasnt sure