About 2 weeks ago and several post here in the forums my trucks Temp gauge pegged out to H and my check gauges popped up on my display screen. However I can turn my truck off and back on and will go to its normal temp but will peg back out after a few minutes again.

I then set my edge to display warnings on the CHT if it reachs over 250.
I drive my truck 15 minutes then the Temp pegs out and within seconds my Edge CHT warning comes on saying the temo is 256. Then a few seconds later the ECT comes on saying my engine temp is 233. However Im thinking its getting a false reading and not over heating. Its not showing any signs of over heating. At this same time I worried to keep driveing the truck till I get it fixed.

Now more bad news I have to wait 30 days to take my truck to have it looked at with the extendend warranty I just bought from FORD. I think it maybe the CHT sensor and was going to just replace it myself till I fould out you have to REMOVE the intake!

So I figured Id wait 3 more weeks and let ford take a look at it and repair it. I just hate not using the truck for 3 weeks.

Then when I take it to ford hope they dont give me any grief for having a CAI on my truck. Because if it is the sensor the CAI will need to come off the truck. If so I kept my stock one and will just put it back on I guess.

Im open for any suggestions here guys.
Thanks!

 

Your truck is 3 years old, have you replaced the coolant?

CHT and "Engine Temp" are in the ~20F degree range so that is correct.

If engine temp reaches ~254F the engine will go into fail-safe and act as an air pump by deactivating 4 cylinders.

 

I recently found several posts (not in this forum) about people with CHT sensor failures. Since you say the truck is not acting overheated, I'd agree this is the problem.

To make matters worse, if the CHT sensor does fail, it "tells" the PCM that things are too hot, even when they're not. So, the PCM, in its "big-brother" way, wants to shut things down to "protect" you. The fact you can restart the truck almost immediately is another symptom of a sensor failure.

Bad news you have to remove the intake to get at the sensor.

- Jack

 

It should be noted that it is the intake MANIFOLD and not just the intake.

 

You are correct I guess I forgot to add the MANIFOLD part or again I would of done the work myself.

I stopped by ford for the other day and asked them about it. One of the techs said he thinks its a bad coil pack? He said hes seen on on a few of the Mark LT trucks.

 

sounds like the thermostat could be stuck closed. when the engine is hot check to see that both your upper and lower rad hoses are hot. if not the coolant is not flowing through the rad and you need a thermostat.

 

Thank you for the reply and will check that!

 

Drove the truck today for 15-20 minutes. Temp gauge pegged out to hot, when I got to work the top hose was hot but the lower hose was not hot at all.

So could it only be the thermostat any think?

Not sure if this help but I added antifreeze to the raditor for kicks. Not sure if its me but looks likes still at the same mark when I added it and color. Does it make since when the thermostat opens it should of flushed it on through or mixed it up a bit?

 

Well, this does sound like a blocked coolant path and it could be the thermostat. But, in your original post, you said once it got "hot", if you turned it off, then on again, it would be ok for a few minutes before acting "hot" again. If the coolant path was blocked, you'd have a hot engine right away on restart.

So, I'm confused (and it won't be the first time). :o

If the thermostat is easy and cheap to change in this beast (sometimes they aren't), it might be a good thing to try.

- Jack

 

heck I dont know anymore and you think your confussed!

yes I can turn the truck off in will go to its normal temp and in a 5-10 minute time period it will peg out again.

I just wish there was an easy test I could try.

Thanks -jack

 

Now I just opened my Haynes manual and it says: "If the engine runs hot...check the temperature of the upper radiator hose. If the hose isn't hot, but the engine is, the thermostat is probably stuck closed".

This makes perfect sense, because coolant circulates through the engine and then past the thermostat into the upper hose. The water pump "pulls" coolant from the radiator into the cylinder block.

So, if you're hot in the top hose, the thermostat's open. But if the bottom hose is cold, you're not pulling much coolant into the block. Is the drive belt slipping?

I'm still confused, but I'm sure it's not the thermostat now.

- Jack

 

Well duh! What if the thermostat were stuck in a partially open position? The upper hose would be hot, but the lower hose might stay cool since there would not be much hot coolant flowing into the radiator.

And, if it's partially open, maybe the stop and start process sort of "flushes" the block.

Suddenly, I'm back to the thermostat.

- Jack

 

There's another "tiny" possibility, that I know can happen, but I doubt in your case. If the lower radiator hose is "soft", the pull by the water pump can cause it to collapse, effectively shutting off coolant flow. This would be especially pronounced when the engine and water pump are operating at higher rpms, but less so at idle. It would probably match up with your symptoms fairly well, but I can't really see how a truck your age would have a soft hose.

You can also get this effect if the radiator is not mounted properly and it shifts back while driving, putting a "crimp" in the lower hose. Has the radiator been worked on lately, or taken out and then put back in?

- Jack

 

the thermostat is VERY easy to change on these trucks. for what its worth id give it a shot. loosen drain plug on rad, drain coolant. follow the top rad hose to the intake manifold and you will see 2 bolts. remove those and the thermostat is right under that peice.

 

Well on the way home yesterday my Engine light came on and its started running REAL rough. Didnt know if I was going to make it home. Like it was only running on 4 cyl. I checked the hoses again and this time the bottom hose seemed much warmer. I'll prpbably just reset my edge to stock to reset the PCM and it will clear the engine light and take it to ford in 3 more weeks. Id like to take it to autozone for kicks now while the light is on and see what code it gives but not sure if I should drive it. shrug

Thanks guys for all your help and input!!!!!!