Replaced radiator and degas. Currently bleeding out air with dummy T-Stat (hollowed out) and front of truck jacked up.

A few interesting observations and some research came up with a few things. When the T-Stat is full open and flowing, the small air outlet hose at the upper drivers side of the radiator will flow at raised RPM. Deductive reasoning says yes its where the air is released to the degas for venting/bleeding. Usually you do not see this as you are driving when this is occurring. Also on flow direction and operation, when cold (closed T-Stat) the flow is limited to circulating through the heater core only as so help bleed out air. A reducer is inside of the heater core inlet hose (usually u can see a factory clamp in the middle of the hose) to prevent over pressurization of the heater core. So direction of flow is as follows:

Coolant flows from pump through the block and heads, up through the intake manifold and out the coolant tube on the top rear of the manifold. Coolant goes through the heater core and through the outlet tube going back under the manifold (ya know through that pain in the *** tin tube) back into the pump.

Now I wanted to know this so I could get a better understanding as to where the air is hiding. As an experiment I installed an A/C QD schrader valve inline on the outlet side of the heater core along with a ball valve down stream of that. The idea is to prevent the air from being circulated back down to the pump and to release trapped air out of the schrader valve (using a servicing tool I got from O'Reilly). The key is doing it at the right time. I have tried it a few different times with some success, that is at times I have seen a significant amount of air released the tube I made up (if you're not understanding I can send some pix to show).

For now I'm just going to run the dummy T-Stat for a few days and see if I get anywhere...

 

I know this is an old thread and I know this is going to sound dumb but every time I have had this problem it's when I adjust the dimmer on the rear view mirror. My mirror has the auto adjust with the slide that leaves the lights on for a certain amount of time when you turn off the car and it's when that is adjust is when I have those problems. Obliviously once I turn off the car and back on it's normal temperature again. just my two thoughts for what its worth and I am probably wrong but sure is coincidental.Maybe its a short in the wires behind the mitrror

 

Interesting ! Strange but interesting.

 

So I just bought an 03 f150 last month and have been doing body work and stuff getting it ready for inspection. Also had some electrical problems with the windows and such. Thought the GEM module was the cause of my electrical issues so I got one from a local junkyard and tried it and it didn't fix my problem. Eventually did find the problem, but anyway, I left that junkyard GEM in and reinstalled the dash and finished my body work. Went to pull the truck out, left it idle for like 2 minutes while I took my tools out and put them on the bench and I heard it start running rough. Went to the truck and temp gauge was pegged, oil temp light was on, and CEL was on. Checked it with a code reader, got p1299. Left the truck sit for an hour while looking at forums just now and then went to restart, temp gauge still maxed out and still running rough. I never had this issue until I swapped out the GEM module. I also had both grounds disconnected right inside the kick panels. I'm going to check my grounds and re-replace the GEM with the old one to see if I still have the problem. Truck ran great before I pulled it in the garage. Now it will barely run at all. Will advise later after I change the GEM.

 

Guys, I'm going nuts and have read everyone's posts trying to find an answer to my exact same problem (code 1299), except that in my truck's case (99 Expedition 5.4 engine), the temp gauge goes suddenly all the way up to H (limp mode) or drops to C (cold) even when driving. I have serviced my radiator, burped the air, replaced water pump, replaced heater radiator, replaced the head temp sensor, thermostat and nothing seems to work! Has anyone have come up with a fix to this false reading?

Thanks a lot.

 

Hi guys, no one replied but hope someone finds this info useful. I resolved the issue and a week later, the problem is completely gone. The false temp code 1299 was being produced by a faulty OIL PRESSURE SENSOR, nothing to do with everything I had replaced that was related to cooling and temperature system!

Don't waste your time and money anymore! Just buy the oil sensor! This was done on my 1999 Ford Expedition with 5.4 engine.

 

Ok, guys , yall have helped me numerous times and I had to finally get registered in as I am a wholesale dealer, and get alot of Ford trucks ,Explorers, Expeditions etc and have fixed alot of problems from this site. This last issue I had on an 03 Ford F150 4x4 with the P1299 code CHT sensor that alleges that sensor not reading right or bad. The one link I finally read, after changing the sensor, by way of taking intake off ,which still didn't correct problem from reading and going in safe mode ,that the engine is overheating 10 sec after a cold start,was to change the Oil Sending Unit as it is paired evidently with the temp sensor as well. I couldnt help to feel sorry for that the guy who took it to a New car dealership and told him he needed a new motor. Those guys are idiots of thinking that they have any care about saving you money or time in solving your problems. Fortunately ,I make alot of money off them when they bring their inop trade in cars to the auction that their own mechanics miss diagnosis or care to figure out to save their own company money. Their fix solution is usually change the whole engine or buy a new vehicle ,unless its a cut and dry problem. Thx EA

 

Greetings all,


Same problem as most posting here. 2000 F150 4.2 V6. Temp gauge pegs hot and oil lamp indicator comes on. Truck is not overheating. Did all the normal overheating fixes including new radiator, new water pump, new hoses, new thermostat, new fan clutch, oil pressure sensor, CHT sensor, flushed the cooling system, burped the radiator. Mechanic is stumped and no one seems to have a single diagnosis or real fix. Currently searching for wiring faults, bad grounds, etc. Has anyone discovered the root cause of this issue? Thanks all. i'll post results of my fix attempts if there are no updates.

 

An update on this 03 F150 ,after oil sending unit was changed. Still going into default limp mode. Here is where I'm at today, with this one. Upon searching and ohming every wire that matters, I saw that after a short rain shower ,water was running under the bottom windshield moulding and dripping over the ledge just above where the computer is mounted. It seems that water penetrated through the computer plug and shorted something in the computer. I brought it to a shop with another new used computer that has ford reflashing capabilities. It should be finished on Mon 9/28/15 and I will update how successful, to prove this problem is fixed. As far as water getting in computers ,unrelated to the F150, I also have an 08 Taurus X with 85k miles ,that I bought inop ,knowing it had computer problems. The computer in those are mounted in the top middle of engine compartmemt just under the windshield moulding and leaked water right on the computer plug and shorted that one to oblivion, so make sure the water coming down off the windshield is flowing correctly along the bottom windshield moulding left and right to the exit passages behind the the corners of the top front quarter panels and not over flowing on your computer pin harness connectors. I had a 99 F450 7.3l Deisel a few months ago, water shorted out 2 (IDM boxes) @ $125 per. They are mounted between the front left fender well ,close to where the rain water is supposed flow. Hope this helps some of the percentages. ERIC, EA Auto Wholesale

 

I'll update results of wiring fault search as well. Will also look for signs of water on computer harness.

 

Hi guys I'm new here and seem to be having the same problem as most of you, I have a 7.3 diesel and the those 2 lights come the oil drip and below it the hot temp gauge on at start of the truck, my heater hand goes to where it suppose to be when its driven and I just drove 200 miles...Once again it doesn't seem to overheat and starts evertime and when I check my oil its also in where it suppose to be Any recommendations guys please And thank you???? I seem to have no leaks coming from any where also!!

 

The computer was the whole culprit in this 160 day saga of chasing the electrical issues the computer had effect alot of different components that threw me to replace the good temp thermister, fuel pump,oil sending unit, intake gaskets and countless hours of checking voltage and continuity of wires and reading every forum on the interweb. Even though I do this for a living and bought this truck not running, I at least know just about everything that matters now on these Ford trucks to troubleshoot a little more quickly.
This is how the order of events took place:
Bought the truck and brought it back to the lot to access
Replaced broke drive belt and tensioner pully
Battery
No Start
Found and replaced bad ECU relay rusty and no good
Truck started and ran fine
Drove it a couple of days and it ran fine
Third day I drove it an emmission code popped up ( no big deal, happens all the time)
4th day I go pick my son up from school and it started raining and P1299 and safe mode triggering entered the picture.
I noticed that the a steady stream of water was leaking between the bottom passenger side windshield moulding right directly above where the computer plugin is located and sealed it.
It got that every time I started it up at that point, different multiple codes appeare, then it only started up once a day.
Ordered a $ 50 used computer
Got another key made, ( Gotta have 2 for the reprogram procedure.
Bring it to the Chinese guys that Ive dealt with for years that have the technology to reflash.
One mech reprogramed but when it started up it would barely run.
Returned obviously bad computer and got another
Mechanic on 2nd computer couldnt get PATS to communicate so NO START
Went to go pick it up because they gave up and found they drained the hot battery I made sure it had for the reflash procedure
Their fired for life with me now
Brought it back and it sits at the lot for another month
I researched for what I need to do to get the reprogram tech diagnostic devices so I can DYI myself.
There is China multidiag out there that will diagnose and have the ability to reflash for 160-400 but most are clones which I found a couple mechanic tech underground hacker type forums that help you with the programs installation to use successfully. Im going to figure how to get that technology cheap without having a $2600 Snapon diagnostic tool.
Finally, brought it to my step brothers shop and they programmed the computer in 30min.
Drove it yesterday and today . Perfect.
Sorry for the long thread, but if I told my wife she wouldnt have a clue, but I thought yall would like the information even if it was too much.
.

 

I have been getting the same code p1299, I have changed the Cylinder head tempature sensor, thermostat, flushed the radiator, changed the wiring harness going to the thermostat, and the computer, and I'm still having the same code up. Is there anyone else who has been having this problem on a 5.4 motor and have fixed it. The dealership had it for two months and couldn't figure it out just seeing if anyone else has had any luck.. Thanks

 

hey folks, i had been searching around looking for info for the past couple months hoping to solve my false overheat issue. i finally solved my issue after trying a bunch of stuff and signed up just to get the info out there in case it can help someone else.

my symptoms were very similar to what others were reporting, sudden spike in temp and limp mode with no other signs of overheating only to be reset by shutting the engine off and re-starting it. every once in a while it would spike and ding but then go back to normal without the limp mode and manual reset but that was rare. i was also getting a report of a cyl #5 misfire but thought that was part of the limp mode and didn't pay it the proper attention. at the same time i had been trying to fix what i thought was a transmission shudder that was actually a fuel delivery issue (i found a great thread somewhere on here with a good explanation of that, sorry no link)

i bought a new COP and put it on cyl #5 (after trying a couple others) and at the same time ran new wires from the cht sensor back to the cpu. in my vehicle the wh/gn wire went straight to the cpu and the gy/rd wire was spliced back in at the cpu because it is shared with several other components. cyl #5 is also the one closest to the chp sensor which now really sticks out to me.

2006 e250 5.4 i had replaced the cht, thermostat, flushed the cooling system. sorry i'm kind of vague with the details, its been a long road and i'm happy to have this behind me, i also realize it was pretty un-scientific to change multiple variables at the same time but i was getting kind of desperate but i guess theres no way to prove it was the COP or the wiring that actually fixed it.

anyway happy motoring, stay safe everyone.

 

okay so i tried everything you guys have maybe a little less or more but i have found that if you take OUT the thermostat it fixes my problem i own the 2000 excursion 6.8 v10 with 169xxx miles. and i tested this theory with a huge hill and it overheated oil temp came of and low gears.. so i took out the thermostat and tried it again and it did NOT happen again! I tested this many times and it works perfect my only problem is that in the winter the heat is warm not hot and it takes a bit longer to warm up.. but thats all... good luck everyone hope this helped!!