Hi Scotty,
I have a 1997 ford expedition xlt 4.6l v8 220,000 miles.
I'm getting random temp spikes for the cylinder head temperature sensor code p1299. A few months ago I replaced the thermostat with a stant superstat because I wasn't getting any heat and that's when it started. I would get some decent heat, but then it would randomly blow cold and shortly after I would get a overheat with code p1299. I pulled over and shut it off and restart and it would go away instantly. So I thought it was a faulty cylinder head temperature sensor and replaced it with a motorcraft one, and along with the coolant temperature sensor. I still got hardly any heat so I flushed he heater core which was hardly dirty. I got some nice heat for about 1 day then it went cold. I have not had heat ever since, and I'm still getting random overheats with code p1299. Yesterday I tried burping the system which worked for maybe 15 minutes but every time I open the cap the coolant reservoir tank just overflows after getting more bubbles out. I can't afford to take it to any shop, please help me!!!
Ps I know it's a false overheat because my coolant temp was only at 167f according to yo my scan tool which I plugged in while I was "overheating"
Your thermostat may be faulty. Get an OEM and replace it.
I agree with Yaser. The thermostat is probably faulty. Get the correct, OEM part and install it. Park the vehicle facing up hill or put the front on jackstands and really get all the air out of the system. Cold temps on the heat cycle indicate air in the system.
Agree. Get the air traps out of the system. It needs to be BURPED! Up hill approach way to go, let idle with the radiator cap off it and watch as you may need to add coolant mix.
Hey guys, thanks for answering.
Yesterday I put it up on ramps and followed a youtube vid which I can't seem to find now, which basically consisted of revving the engine to 3500rpm for 30 seconds and idle down for 15 seconds then shutting the truck off. It burped out alot and I got some wicked heat. I drove it a few miles and air went cool, then code p1299 reared it's ugly head again. Scan tool was plugged in when I was driving and it was again reading temperature at around 167f. I shut the truck off and started it back up and the over temp light and gauge went back to normal. No warm air has returned yet. The intake hose to the heater core is piping hot and almost cold on the output. It's not clogged because I just flushed the damn thing. I will replace the thermostat again but I'm scared I got a blown head gasket now because it seems like there's an endless amount of gas building up in the system, whether it's air or not I have no idea without getting it tested.