This is what I got :

P1299 Cylinder Head Over Temperature Protection Active (Ford)

5-10 miles after cold, check engine comes up, then temp warning light, then the gauge goes red. Then it dumps abour quart of coolant through the radiator cap (16 psi). Engine stutters. Next start is fine.

If I leave it warm up in idle, all's fine.

Mechanic replaced thermostat, coolant and radiator cap.

2 days later - same thing.

What else could this be?

Truck runs great otherwise...could not find much on this.
Thanks!
97 4.6

 

When did this start? Was everything ok before the problem?
If you are in fact dumping coolant in a manner that is indication a real cooling system problem, solve for that and the response to it should go away.
Cooling systrem pressure test.
Test for exhaust in coolant.
Is radiator partically internally blocked?
Is the temp gage going up when this happens?

 

No problems before and once the engine is hot no problems again.
Just drove from NM to TX - again, the truck ran great.

So far it happened twice. Once before the thermostat change and
once after.
All I have to do is refill the coolant and restart the engine.
And it only happens when starting cold - in about 10-15 minutes.
Heater blows hot too.

Shows only one code - P1299. Releases about a quart of coolant on the ground.

Any ideas?

 

And the cooling system was tested for leaks - nothing, holding pressure OK.

 

Check and make sure your top radiator hose is not collapsing. I just saw that cause a phantom overheating problem on an S-10 blazer that had the thermostat changed and radiator flushed to cure the problem.

Just a thought