P1299 (cylinder Head overheat)

[sgtsandman]

immediately is exactly how long?? 2 sec, 5 sec, 20 sec ?? 1 minute??
I would think it is damn near impossible for the actual head temp to change in just a few seconds.
what was the dash temp gauge saying? edit: oops you already said it spiked

unrelated, does the 2.5 have any more/less power than the 2.3 did? gas mileage the same?

It depends on the 2.3. More than the 2.3 Lima but less than the 2.3 Duratech.

 

[sgtsandman]

I'm fighting the urge to shotgun this and not know what the actual fix is. Since the issue is intermittent and the engine is so forgiving, try changing the temp sensor first and see what happens.

Also, test the fan clutch operation. Stone cold, the fan should be hard to turn by hand. Start the truck and let it run about two minutes, then shut it off. The clutch should have unlocked and the fan should be easy to turn by hand. Lastly, take it for a drive and get it up to full operating temperature. The fan should be hard to turn by hand again.

If that checks out, then move to looking at the thermostat and the radiator. Being that the engine has a cast iron block and head, it can clog up the radiator over time without the coolant looking rusty but take it one step at a time and cheapest fix to most expensive doing one thing at a time so you know what fixes the problem.

 

[DaveH]

thanks for your input. I'll try those checks. I did a flush of the system and the coolant that came out looked like fresh out of the bottle. I doubt the radiator or the engine are clogged. Fan clutch and sending unit up next. I truly think this is an electrical glitch as the last time it happened I was watching the temp gauge. I was shocked, thermodynamics doesn't act this way. After the flush I ran the truck uphill and pushed it to 4K in passing gear. After 10 or 15 seconds the temp gauge spiked instantly! Normal then topped. I backed off to about 2500 rpm and after about 5 seconds it dropped to normal again. I pulled over and checked the motor and radiator. They seemed normal operating condition.

 

[pjtoledo]

cylinder head temp and instrument panel temp (coolant temp) are 2 completely separate circuits.
the coolant temp sensor is on the rear of the cylinder head where the big outlet is.

in the 2005 wiring diagram the engine coolant temp sender circuit starts at pin 6 of the
instrument cluster, thru the sender, then on to ground.

the cyl head temp sender goes to the PCM pin 66. uses circuit 359 signal return that is common to lots of components.

they don't share a common ground point, according to the diagrams, but exactly where do they ground???

long shot question: since the 2 senders are close together and in the head, what's the chance
of a steam pocket in the head? is the cooling system pressurized properly?

 

[DaveH]

My weakest DIY point is electrical. Just never had exposure to it. To answer your last question, I did flush the system. I drained, filled with distilled water, ran to temp, burped the system and drained again. Refilled with chemical engine flush and more distilled water ran to temp both times with heater on high. Drained a third time and filled with coolant. I burped the system and filled with heater on high. Ran it a few miles and returned to the house topping it off. Pretty sure all air pockets are out of the block and cooling system. Would be interested in looking at those diagrams to see if I could trace the wiring in the truck.

 

[pjtoledo]

steam pockets are self generating. whenever coolant gets above it's boiling point at a localized spot a pocket can form.
when the steam cools to below the boiling point the pocket collapses, it leaves no evidence it was ever there.
anti freeze and pressure both raise the boiling point, so a steam pocket should be a rare occurrence.

there is a small orifice in the nipple of the upper cooling system that should vent any vapor/air directly to the reservoir.
if there was air in the system it should go away during normal operation.


what's the thermostat rating? I'm running 192.

you mentioned an IR thermometer in post 9, use it to check the temp on that big metal tube near the rear. that's the output from the head.

 

[DaveH]

I'll check that tube next time I run the truck. Thanks much for your feedback!