I have yet to see a definitive answer. I have a 2003, SCREW, 5.4L, with many miles on it. Around 163K. At times, when I park it and return within a few minutes, it goes in to the overheat routine with all the normal symptoms. There is NO coolant loss. Right now, while I try to get it sorted, there is no thermostat. Yes, I know. It has been out (this is a new one I installed last week) for two days. As soon as I get the problem solved, the thermostat will go back in. The problem happened again today. When I turn the swith on, it does it's little act. let it run for two minutes or less, turn it off, turn it back on and everything is ok except the "Check engine light" stays on. The code is the one about high cylinder head temp. I am pretty much convinced that the good ole boy that owned this truck ( 83) probably replaced that sensor with one intended for use on a light. It has analog but also acts like a switch. Anyway, I need to know where the sucker is, and I need to know the shortest route to it. I've only owned the truck about two months and can now replace the thermostat in 20 minutes, complete. Need guidance or I might do something stupid. (here Chevy, Chevy, Chevy. Come here boy....)

 

Just have to ask this: Did you 'burp' the cooling system after doing the thermostat change? This could EASILY cause the overheating after shutdown problem due to hot air and steam getting to the CHT sensor instead of warm coolant.

IIRC, the CHT sensor is right under the alternator and threads into the cylinder head water passage. It should be fairly easy to remove and replace.

The first thing I would do is to replace the thermostat and then 'burp' the cooling system properly (elevate the front end slightly, keep the radiator cap on loosely, let engine run 15-20 minutes, and add fluid after the thermostat opens to the fill mark). ONLY after making sure that it was 'burped' properly would I then suspect the CHT sensor.

 

First...step away from the Chevy!

Then x2 on the burp, makes a world of difference.

Next when it is warm/hot see if you can notice a difference in the temprature of the radiator at the top vs. the bottom. Some times they fill with sludge/stop leak and it diminishes the radiator's ability to cool.

Good luck.

 

Don't let your truck hear that.

 

This could EASILY cause the overheating after shutdown problem due to hot air and steam getting to the CHT sensor instead of warm coolant.

IIRC, the CHT sensor is right under the alternator and threads into the cylinder head water passage. It should be fairly easy to remove and replace.

The first thing I would do is to replace the thermostat and then 'burp' the cooling system properly (elevate the front end slightly, keep the radiator cap on loosely, let engine run 15-20 minutes, and add fluid after the thermostat opens to the fill mark). ONLY after making sure that it was 'burped' properly would I then suspect the CHT sensor.[/QUOTE]

Got it!! Your message I mean. Guess I am not communicating well. I changed the thermostat after the problem started. If the sensor is right under the alternator, why do I not see it OR the wire going to it? I do appreciate your input but I've owned Fords before. This one has me truly baffled. Just to let you know, I've already fixed the heater A/C control in the cab, and the compass, and installed a K and N air filter AND changed the spark plugs.

 

Really like my Ford but it will hear worse than Chevy if it don't get it's act togeather. I might even say T o y o t a in it's hearing, as in replace with.

 

I am not putting this thing on my shoulder and patting it on the back. So how does one burp a fully grown F150?

 

If you do get it up on your sholder and can get it to burp like that then you better have pics or a video !!!!!

Fill the cooling system and turn the heat on the hottest temp. Fire that bad boy up with the radiator cap loose/off and let it idle. as it warms up it will start to push fluid either into the reservoir or out the top, don't worry. When the thermostat opens the coolant level will go down in the radiator, remove the cap at this point and fill to about a 1/2 inch below the fill hole and let it continue to run with the cap off. As the thermostat cycles the coolant it will be able to ( are you ready for this ) BURP the excess air out of the system. Every time air goes from the motor to the radiator the fluid level will go down.

Once the engine has reached full operating temp for a few minutes then top off the coolant ALL the way to the top and replace the cap. then fill the reservoir to around the middle between cold and hot levels. As the system cools it will suck from the reservoir into the radiator to make up for the contracting coolant which keeps air out of the system.

When the system is completely cold then you can fill the over flow reservoir to the proper level.

Takes about 15-20 mins and much easier than the sholder routine! But I would still like to see that method in a vid!!! ha ha ha

Good luck sorry about the long explaination-didn't want to play forum tag with little details.

 

lmk if you need someone to take a look at it, im local to you and might be able to help

 

Update:
It is always full. Has no coolant loss. I can pretty much take the cap off any time I wish. Not a lot of pressure. The top hose gets hot, otherwise I would think the pump is not working.

Man!!!! No wonder.....uh.......there is no, repeat no thermostat. There will be no, repeat no thermostat until system is working properly.
Using your method, it should have burped all it was going to a two weeks ago, Wednesday. I still am not putting it on my shoulder. I remember what a mess a itty bitty 6 pound girl made. Can't even imagine the truck.


I pulled a connector on the wire I thought was the temp sensor. Hooked a 50 K pot to it. It more or less worked as advertised. Checked ohms across the terminals and it reads much less cold then the 58K the book says. It reads about 8K. finally got enough stuff out of the way to look around the alternator. nothing under except some threaded holes that may have been it in a former life. No wires, the only harness goes under the intake manifold and apparently back to the back. No. idea where. I just find it hard to believe that the Ford dealers won't talk to me about it, only charge me a $100 to look at it. And you guys, you are the proven experts. so tell me where the sensor is and how to get to it. Please..........or I'll write you a love letter and sign it Toyota.

 

That would be absolutely fabulous!!.. Will there be a charge?

 

You're probably more right than you want to think. Most likely the water pump has eroded impellers and is not pumping the coolant like it should. Yers would not be the first. I'd suggest a new pump.

 

depends on what all happens. Here's some information straight from my Ford Service DVD.

 

DL1 DTC P1288 OR P1116: CHECK OPERATION OF CYLINDER HEAD TEMPERATURE SENSOR
Run engine at 2000 rpm until engine temperature becomes stabilized.
No Starts or Vehicle that Stalls:
GO to DL3 .
Check that upper radiator hose is hot and pressurized.
Rerun Key On Engine Running (KOER) Self-Test.
Is DTC P1288 or P1116 present?
Yes No
For LS6/LS8 and Thunderbird with Electronic Throttle Control: GO to DL3 .

All Others: GO to DL2 . Engine temperature was not stabilized. REPAIR any other DTCs as necessary.



DL2 CHECK VREF CIRCUIT VOLTAGE AT TP SENSOR
Disconnect throttle position (TP) sensor.
Note: GO to Pinpoint Test DH and refer to Pinpoint Test Schematics and Connectors for TP harness connector pin-out information.

Key on, engine off.
Measure the voltage between VREF and SIG RTN circuits at the TP sensor harness connector.
Is voltage between 4.0 volts and 6.0 volts?
Yes No
There is sufficient VREF voltage. RECONNECT TP sensor. GO to DL3 . GO to C1 .




DL3 CHECK RESISTANCE OF CYLINDER HEAD TEMPERATURE SENSOR WITH ENGINE OFF
Note: IMPORTANT Marauder Only - See pinpoint introduction for ECT\CHT information.

Disconnect CHT sensor.
Measure resistance between CHT signal and SIG RTN pins at the CHT sensor. Refer to the table at the beginning of this pinpoint test for resistance specifications.
Is resistance within specification?
Yes No
For No Starts or Stalls, RETURN to Section 3 , Symptom Charts.

All others, GO to DL4 . REPLACE temperature sensor.




DL4 CHECK RESISTANCE OF CHT SENSOR WITH ENGINE RUNNING
Note: IMPORTANT Marauder Only - See pinpoint introduction for ECT\CHT information.

Note: Verify that engine is at operating temperature before taking readings.

Run engine for two minutes at 2000 rpm.
Measure resistance between CHT signal and SIG RTN pins at the CHT sensor. Refer to the table at the beginning of this Pinpoint Test for resistance specifications.
Key off.
Is resistance within specification?
Yes No
REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ). REPLACE temperature sensor.




DL5 DTC P1289 OR P1290: ACCESS CHT PID AND CHECK VOLTAGE
Note: IMPORTANT Marauder Only - See pinpoint introduction for ECT\CHT information.

Connect scan tool.
Key on, engine off.
Access CHT V PID.
Is the CHT V PID less than 0.2 volt?
Yes No
GO to DL6 . GO to DL7 .

 

DL6 CHECK FOR GROUNDED CIRCUIT
Note: IMPORTANT Marauder Only - See pinpoint introduction for ECT\CHT information.

Disconnect CHT sensor.
Key on.
Access CHT V PID.
Is the CHT V PID more than 4.6 volts?
Yes No
REPLACE temperature sensor. GO to DL21 .




DL7 CHECK FOR OPEN HARNESS
Note: IMPORTANT Marauder Only - See pinpoint introduction for ECT\CHT information.

Disconnect CHT sensor.
Connect a jumper wire between the CHT signal and SIG RTN circuits at the CHT sensor vehicle harness connector.
Key on.
Note: If a Scan Tool communication concern exists, remove jumper wire immediately and GO to DL12 .

Access CHT V PID.
Is the CHT V PID less than 0.2 volt?
Yes No
REPLACE temperature sensor. REMOVE jumper wire. GO to DL11 . KEY OFF.





DL10 DTC P0118: SIMULATE OPPOSITE SIGNAL TO PCM
Disconnect CHT sensor.
Connect a jumper wire between the CHT signal circuit and SIG RTN circuit at the CHT sensor vehicle harness connector.
Connect scan tool.
Key on.
Note: If a Scan Tool communication concern exists, remove jumper wire immediately and GO to DL12 .

Access CHT V PID.
Is the CHT V PID less than 0.2 volt?
Yes No
REPLACE CHT sensor. REMOVE jumper wire. GO to DL11




DL11 CHECK CHT SENSOR SIGNAL AND SIG RTN CIRCUITS FOR OPEN IN HARNESS
Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

Disconnect PCM.
Measure resistance of CHT circuit between PCM harness connector pin and CHT sensor harness connector.
Measure resistance of SIG RTN circuit between PCM harness connector pin and CHT sensor harness connector.
Is each resistance less than 5.0 ohms?
Yes No
REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ). REPAIR open circuits.




DL12 CHECK CHT SENSOR SIGNAL FOR SHORT TO VREF IN HARNESS
Key off.
Disconnect PCM.
Measure resistance between CHT and VREF circuits at the PCM harness connector.
Is resistance greater than 10,000 ohms?
Yes No
REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ). REPAIR short to VREF.