I have a potential problem I wanted to get some folks thoughts on. I have a 2006 FX4 5.4L that has just started to show signs of overheating.

I have an Edge that is monitoring Engine Coolant Temperature (ECT) and Cylinder Head Temperature (CHT). I also have 2 Autometer coolant temperature gauges with one sensor in the upper radiator hose and the other one in the lower radiator hose. I monitor the gauges pretty closely while driving. Normal readings for me are:
-Edge ECT = 198-200 degrees
-Edge CHT = 200-202 degrees
-Upper Radiator Hose = 195 degrees
-Lower Radiator Hose = anywhere between 100 and 190 degrees depending on outside temps and how hard the engine is working.

A couple of days ago (while towing a 6000# trailer) I had the Edge ECT starting to climb to 212 and the CHT to 226. Upper Rad Hose was rock solid at 195 and the Lower Rad Hose never got above 160. This seemed normal to me since it was towing a heavy load, but in past towing experience with same trailer I have never had CHT that high.

When I unhitched trailer and drove truck again, the high ECT and CHT readings continued. Cruising at 45 mph on level ground, I get ECTs up to 212-214 and CHT up to 220-222 with Upper Rad Hose at 195 and Lower Rad Hose 100. Worse yet is at idle for a few minutes, ECT goes up 215 and CHT to 230. When I rev throttle to about 2000 rpms the temps quickly come back down. I did not want to let it idle for too long for fear that it would really overheat.

The Edge has not captured any computer codes and it is not engaging Fail Safe mode. Trucks drives just fine but the high temperatures suggest something is wrong. The temperatures of the radiator hoses appear to indicate the fan and radiator are doing there job. Carefully watching the Upper Rad Hose I can even see temperature blips as the thermostat opens.

Anyone have any ideas on what I should be looking for?

Not sure if it is related or not but about 2-3 weeks ago the truck developed a very loud ticking (almost knocking) noise. I was starting to think is was the cam phasers going but the noise went away before I could do any trouble shooting.

 

if your engine temperature climbs but your radiator doesn't it probably means that your thermostat needs replaced, right??? It sounds like its not opening up properly...

just using some logic here... I have no experience to go from on this...

 

Replace the thermostat and go from there.

 

This one thing causes me to believe it's fan clutch. I've had experience with air flow issues 3 or 4 times and that's what it was each time. Don't be fooled by the age of the FC. Meaning they can go bad at any time. Adverse conditions will reveal the problem. I had a motor home that would quickly go to 230 when backing into my pad in the back because of NO ram air flow. As SOON as the temp hit 230 the clutch would kick in and cool it down. Never had a problem when there was forward ram air flow.

 

The cooling systems in our trucks are pretty good and do a great job of hiding fan clutch issues, until you apply a good load to the truck. Such as towing or plowing. I've already replaced mine once and the motorcraft replacement isn't to robust either.

Mine was so bad that I could stop the fan with a heavy leather glove when the motor was idling.

 

Thanks guys, it was the thermostat. I replaced it this morning and temperatures are back to normal. When I took out the old thermostat it actually separated into 2 pieces.

 

Picture of old thermostat:

 

glad it worked!
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