Please, I'm at a loss here! I have a 04 Lariat w/ the 5.4 3-valve engine. I had 205,000 miles and spun a main bearing. Installed a rebuilt long block. now has 12,000 and has been running great until two weeks ago while on a trip, the temp gauge pegged and message center said going to reduced power. Pulled over and checked under the hood, nothing hot, belt wat fine, no leaks. Started back up, guage was back in the normal range (straight up) and all was good for next 5 mile, then botta boom, botta bing, same thing! Again, checked everything under the hood, all was ok. Re-started and gauge was normal so down the road I go. within 3 miles it happens again. This time I just coasted to the shoulder and shut the truck off and waited a few seconds then re-started the engine. The temp guage was back to normal and the message center was cleared again. This went on until I took it to a Ford dealer about 45 miles down the road. They found nothing wrong, but said they thought it was a wiring harness problem since I had the engine replaced by someone other than Ford.????? Anyhow, drove the truck for 3300 mile without a hitch, then it started again. This time I stopped and checked for leaks, broken belt or collasped hoses. Still nothing. As before, if I would re-start the enginge it would clear it and all would be good for 3-5 miles. After pulling over 9-11 times and finding nothing, I drove it for abount an hour-1/2. The computer must not have liked that because it shut the engine down and the check enging light came on. I pulled over and checked under the hood, still not running hot. Re-started and drove the rest of the way home. I took the truck to shop and found the code was for the right head over heating. While they had it there, they checked the wiring harness and found a chaffed wire, so replaced the complete harness. Thought for sure that was it. I picked up the truck and drove it 19 miles and it started all over agin!?!?!?!?!?!?!??!
I can't beleave that the engine needs burped after driving it 12,000+ miles, I'm more inclined to look at the engine ground or the guage cluster. Any suggestions would be appreciated.

Txphantom

 

What do you mean burped ? Did someone tell you that ? Your post mentions nothing about a possible coolant problem.

 

Yah that was random. A chaffed wire, replaced harness. Code for right side cylinder temp high.. then BaM... can't believe it needs burped after 12k miles.

I'm no professional, and not a certified mechanic but when I did my swap, I checked and double checked things over and over for weeks following. Making sure no fluids were low. And being it had sat for a while, changed all the fluids after 500 miles. Then went to regular changes. Coolant can be a bit tricky filling up a new motor. I needs to be thoroughly burped. Yours may not have been done properly. Is it possible the CHT sensor is faulty? If it were me, I would check the temp with a secondary source to verify whether it is overheating.

 

Toyz, thanks for the input. Will check the CHT sensor.

 

So I guess that was a miss-print ?

Well, good luck .

 

Jbrew, the shop had replaced the coolant and Burped the system before the truck went on the road. As of today, the coolant level is correct and has been burped..... again. Still getting false reading.

 

Is the degas bottle or upper radiator hose getting pressurized when this happens. You may want to have the coolant checked for hydrocarbons as well just to eliminate a headgasket concern. These engines are sensitive to refilling, one large air bubble and it will move around and drive you nuts.

Hey jbrew anytime I can use the "degas bottle" phrase I jump on it ha ha.

 

Well, I guess you wouldn't know , -how they purged all the air gaps in the core and heater hose lines. They're higher than the Degas bottle (expansion tank), which can make it a PITA bleeding out.

Ford Service doesn't have a full proof procedure. BUT, there's a TSB on it. ~


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I'm not saying you have trapped air in the system. Just that, if you do, trapped air creates hot spots in the system.
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BTW,-The CHT has it's own harness that branches from the engine harness. Not only does it disconnect at the sensor, but it has another connector @ the branch. So it can be completely disconnected for checking.
The reason why they do that is because the CHT is a pita to get to. It requires removing the alternator, maybe even the intake. With the extra connector you can disconnect at the branch rather than the sensor if you need to work on the engine harness. You could pull the entire engine harness fairly easily and troubleshoot on the bench, fix wires then re-rap.

 

I know it, you really fancy that word don't you.... - Yea, I used it as well. Couldn't pass the degas up, given the opportunity.

 

Ok guys, thanks for all the input. I think we'll try burping one more time, maybe pulling the truck up on some ramps to get the radiator a little higher. I have replaced the harness, any way to test the CHT while on the block?