Hi I have a 2003 4x2 with the 4.6L V8 that has been giving me headaches for a week now. It started to over heat but on the gaage as soon as it hit the red which would only stay there no more then 3 seconds then would go back down to the middle where it normally runs. I did have some boiling out of the radiator over flow cap. So I checked fluid levels and it was good. I replaced Thermostat (twice) and that didnt solve the problem. So next I replaced the radiator and that solved the problem temporarily. Then it start to run crappy and missing bad. Was thinking of great blew a head gasket. No water in the oil and also did the exhaust fume test on the raditor over flow cap 5 times this past weekend to see if any exhaust was present in the antifreeze. Nothing!!! So not sure what the hell. I was told yesterday by co-worker he had same issue on his 5.4L and it turned out to be a small crack in the (PLASTIC) intake manifold which causeed him some over heating and blowing 3 coils in a week??? Has any one had any issues similar to mine? I am lost on this and the shops cant seem to pin point the problem. Going today after work to have a compression test done on the cyclinders to see if head gaskets are good or not. Then will look more in to the plastic intake. Damn first time the truck has given me any problems and now its a real pain in the rear!!!!

 

Overheating usually causes the PCM to alternatly shut off cylinders' fuel as a self protection measure once overheating begins and the engine is still running. This pumps air through and limits heat production.
The temp gage intermittant is often the lack of coolant in the sensor location. It alternately gets coolant then steam until the thermostat opens.
Has the cap been changed?
Most all cooling systems depend on the system operating under pressure to raise the boiling point of the coolant.
Are you sure all air has been purged from the system and are any codes set?
If all thses are addressd then it is possible the water pump has given up.
Good luck.

 

Yea the guage goes hot then in less then 3 seconds its back in the middle where it usually sits. I have purged the system so many times till all purculation stopped. Now I can see the water circulating in the over flow bottle so wouldnt that rule out the water pump?

yes there were codes on Sat that were ONly showing cylinder 7 and 8 with misses. Those are the ones that also had small amount of water sitting near them between the head and intake.

 

Address the cylinders that may be missing next.
Is it coolant in the plug wells or outside?
Look at the heater hoses just above those cylinders' plug locations as a possible source of a leak.

 

yea ended up changing cyclinder #5 coil and rough idle went away. But still have the water boiling over. So far mechanic thinks head gasket building up back pressure in system. truck going into shop tomorrow/ hoping its the intake inside of having a head job.

 

That spike in the gauge up to red, then drop back is common on a leaking head gasket. You burn off some antifreeze, then get a air pocket in the water jacket. When the air hits the temp probe, the gague spikes red hot. About that quick water hits the probe and the gauge drops back to normal.. System is full of air, probably due to head gasket or cracked head. I also had a crossover tube o-ring fail on the 5.4 motor.. but that causes external water leak and you will see it in the VEE.. If not repaired, that will lead to a failed head gasket due to low water level, overheating.

 

So far the truck was tore down and it wasnt the intake leaking. They think it may be a crack in the head. So heads are being sent to the machine shop this morning. Not the expense I was needing right now with kid right around the corner!