sadaly

My F150 overheats from time to time. This truck is not my primary driver. It has 135K and I just flushed the cooling system and replaced the thermosat. The heat sensor pegs out and then drops to a normal level. It has blown fluid when hot. Several months ago I had the truck serviced with the same issues. The garage replaced the an intake gasket. They thought that coolant was linking into the #1 cylinder. But couldn't be sure. I don't see any leaks but the coolant must be going somewhere. I have checked the oil, nothing there. Any ideas?

Good old Bill

As I understand your problem, you loose coolant and it overheats, is this correct? If the shop who replaced the intake gaskets did so because coolant was in the cavity under the intake, this could also be caused by head gasket leakage. As I am not qualified on this engine, there have been others with reported leakage in this area. Suggest trying the search button for further info. Might try head gasket leakage 5.4L

ranzo

Sounds an awful lot like a head gasket. run a Pressure test on the cooling system to see if it holds pressure. Aslo you can let it run till operating temp then let it sit for a few hours then pull spark plugs to see if they have signs of coolant on them or if there is coolant on the piston.

sadaly

Thanks guys. Good old Bill and ranzo you both are tracking correctly. It is my understanding that removing the heads on a 2000 5.4 is a MAJOR undertaking. The pressure test will be my next step..

sadaly

Well, we ran a pressure test at the dealer. No pressure drop in 3 hours. I drove the truck 30 miles on day 1, no problem. Day 2 drove 6 miles, parked. no problem. On the return trip, at 3 miles the temp gauge was pegged, oil light came on for 30 seconds and temp gauge dropped to normal. I drove it home. I could smell anti-freeze, so I popped the hood. Upper rad. hose was rock hard from pressure. I opened the reservoir it released slight pressure and the coolant drained away from the reservoir. I haven't driven it since. Any ideas? I found thoughts that if you place the intake gasket that the intake should be replaced as well. Could the intake still be leaking into the #1 cylinder and causing a lack of coolant?

vanman

I have the exact same problem. I have been researching it for days. The coolant loss is from the radiator cap.There appear to me to be air pockets in the system, but sadly I think it is exhaust. The reservoir smells like it. The likely situation is a head gasket is pushing combustion gases into the cooling system . This would make sense, since the pressure is higher in the cylinders that the cooling system (2000 psi vs. 16psi). The puzzling part is that it can run for hours without a problem, once it is properly warmed up. The van has a rear heater, which can trap an enormous amount of air. I found a small leak in the line, which I fixed. The thermostat that was recently put in has no air hole. I am going to try one more replacement thermostat and make sure the system is full. If that doesn't do it, it is off to the Ford dealer. I think I will have them start by probing the cooling system for exhaust with an exhaust gas analyzer. Anybody know how much a valve job costs for a 5.4?

sadaly

There is a chemical test that can be performed to determine if exhaust gases are in the coolant. I have had it done and it shows gases. A local radiator shop did it. 6 shops have looked at the truck, 3 won't do the head job. It takes 24-26 hours. In the F150 the engine needs to be remove to complete the job. I am having 1 last guy look at it and then determine what my plan is. The job is around $3200 to have it done. If I can get for $2000 I'll do it. If not I'll keep adding coolant and drive it until it drops.