hello, my truck is a 1997 ford f150 with the w code 4.6l, it just has a heater no a/c, well i was driving my truck and it over heated, i pulled over the side of the road and i opened the resevoir tank up and it was bone dry, so i closed it and prayed that i would make it back home, wich i did and it ran fine, i was doing 55mph! lol. well when i got it back home i filled it up, and the next day i was driving it and the temp gauge went up again, so i pulled over and opened the hood and noticed that the coolant blew right out of the cap on the resevior, so i opened it and looked inside and obviously when all of it blew out it was low on coolant again. so i got back in and drove it to family dollar and put coolant back in it. the truck drove fine for a day. now today i was driving back home from work and it started blowing cold air and then the temp gauge went up again and it looked under the hood and it blew out of the cap again on the resevior, i have no idea what is going on, thermostat maybe? air bubble?

 

Thermostat.

 

yuup sounds like you need a new thermostat

 

Well I am working on this same problem.It could be a t-stat, also you could now have air in your system, or a bad head gasket.I though mine was my water pump as I took it off and it only had one fin left on it.Well ran good for about 350 miles and over heated again.Have done a hydro carbon test and is was negative again, but just got a misfire on #7, so am going to pull that plug and look at it.I have a feeling it may be steamed cleaned or have coolant on it.

 

well i changed the thermostat and it did not fix the problem. I drove it for less than 8 miles and i had the heater on full blast and the pedal to the floor and it overheated again. im thinking an air bubble but how do you get an air bubble out?

 

run the truck, with heater on full blast. remove reservoir cap, and using a glove or similar insulator, grab the top coolant return line and pinch it shut. its known as gulping. air bubbles should "gulp" out of the reservoir

 

well thank you guys very much for your help, as mentioned i changed the thermostat and i got rid of the air bubbles and the truck is running fine. This has to be one of the best websites for f150 help, info, and just plain sick rides, thank you very much for your help cause i thought i was going to have to change a head gasket, but with your help it was only a thermostat and air bubbles, thanks again

 

I'd recommend changing the cap as well if its been over heated a couple times, plus its 13 years old now