03 f-1504x4 5.4 69k miles. Start truck in mornin warms up blows hot air. 3 or so miles blows cold air. Gauge stays in middle of range. Another mile or 2 gauge jumps way up, then comes back to normal and starts blowing warm air again. I have put 2 new thermostats in so far. any help will be appreciated.

 

What temp are the thermostats?

 

180 i think what ever o'reillys or advanced gave me

 

I assume that your 03 is like the later 5.4s. They come with 195 and need it to operate efficiently. I may be wrong, but I think your coolant is not as warm as it needs to be when your thermostat opens.

 

I will check on temp of thermostats. Was told could be head gasket but a mechanic from a ford dealer was'nt convinced it was . I thank you for the information. Randy

 

welcome to the forum
What you have described is a low coolant level. Question is. Where is the coolant going?

The usual place is head or intake gasket.
Alot of the times the cause of this is using the wrong antifreeze.
How does it look inside the radiator. Is it coroded in there?

 

Yeah it sounds like you are running low on coolant. It is possible that you have a bad radiator cap, if you have changed out the t-stat already. When you changed the t-stat out did you get all of the air out of the lines?

 

Could be a faulty clutch on your cooling fan.

 

I vote for an air lock in the cooling system. It has to be properly "burped" after any kind of draining and/or thermostat change.

 

Thanks for the response gentlemen but, I've got one local hotshot mechanicthat works at a ford dealership saying its head gaskets. He also says that motor is why he drives a chebby! I am getting air in system. I also have another mechanic at another dealership thats gonna run the vin number and see what happens. He's still not convinced its a head gasket. Do you really have to pull the cab to replace head gaskets. Again thanks for the help. Randy

 

I haven't heard that one

 

I don't know about the cab , but I would definitely pull the motor before I pulled the heads - It's allot easier and there's not much to it..

 

before you pull heads take it to a competent mechanic
there is a kit that you place over the opening where the radiator cap goes-it contains a solution that will chage color if exhaust gases are leaking into the cooling sytem due to bad head gaskets.

the easier way is to stick an exhaust gas analyzer over the open neck of the coolant overflow tank. it will determine if there are exhaust gases in the coolant.

doesn't sound like your hot shot Ford mechanics are very smart or technically competent

 

I tried a test today. Pulled the hose off between the radiator and de-gas bottle.Clamped the bottle hose shut. Put a piece of hose on radiator and run end of hose into a bottle filled with water. Started truck ....... small burp of air in the water bottle on a fairly consistent rate. Truck goes tomorrow to have heads pulled. Again, people Thanks for the help. Randy

 

That's not enough proof to me that pulling the heads is necessary.