I have a 97 F150 4.6 with about 150,000mi and lately my cooling system has been acting up. With the cold Minnesota weather, starting out in the morning things will heat up normally for the first 5 minutes of driving and I will get a little heat. Then the temp gauge drops and all I get is cold air for another 5 minutes or so. After this, the temp gauge goes all the way up to the HOT range (occasionally the temp warning light will come on), stays there for a few seconds, then drops back down to normal. At this time I usually start getting heat again. After all of this, the heat remains constant.

I have tried changing the thermostat, but the same thing is happening. Any thoughts on this?? Bad thermostat?

Thanks for any replies.

Steve

 

Is there coolant in the overflow reservoir?

Have you tried burping the system?

 

Well, I've put in my second thermostat (I'm starting to get really good at it), but it's still doing the same thing. I have brought it up to running temp and added coolant until everything stabilized. I do catch a whiff of coolant in the cab when I stop and I have been losing some fluid, so I must have a leak somewhere, but haven't been able to spot it. Since I smell it only when I stop, I'm thinking the leak must be somewhere in the engine compartment, and not the heater core. Could it be that when the engine cools off, say overnight, that air could be drawn into the system through this leak causing an air lock and the unusual temp gauge/air temp problem? Does this sound logical?

Anyway, I'm about ready to take it in to have the leak located and repaired, unless someone else has some ideas.

Thanks!
Steve

 

Did you resolve your heat issues? I have changed the thermostat still have the same problem. Any help would be appreciated!!

Thanks,
Gene

 

Resurect the dead

 

Yes, I did finally resolve my issues. Shortly after my first post, I found out that I had a blown (head?) gasket and the combustion pressure was blowing the coolant out of the overflow. I fixed the problem by getting what I could for the truck, and buying a used Silverado. No more cooling system problem!