Towing overheat today.
 

*Bing Bing Bing* I looked at the message center and saw "CHECK GAUGES" a quick visual revealed the temp gauge pegged to the right. Looked over at my Edge and saw 260* on the CHT. What the hell, it's like 34* outside today and I've towed in the summer before with no issues at all. Pulled over and popped the hood. No coolant loss or leaks, coolant tank full, no hiss or steam, the engine didn't even feel like it was very hot. By the time I got back in the seat the temp was 228* and dropping so off I went again. Few minutes later the same problem. Couple things I noticed. On level ground and fairly low RPM my temps would climb. Whenever on hills and the truck down shifted to 3800-4000RPM my temps would acyually drop over 20*. I managed to keep my foot into it for the remainder of the trip and had no further overheat problems. So now I'm trying to piece together why this happened. I think it's unlikely the water pump impeller would fail seeing as it's steel, so my suspects are the fan clutch or thermostat. I'm open to advice, experience, or suggestions before I begin buying parts. :cursin:

At highway speeds (+45mph) the engine cooling fan is not needed, the air current should be enough to keep thinks cool. So that makes think that it could be your water pump, the high RPM's might be enough to overcome a slipping/ broken impeller.

Changing the thermostat is very easy and inexpensive, so that might be worth a shot.



When it was overheating was your heater blowing warm air?



Reason I ask is because typically when a head gasket fails the heater will quit working first because the combustion gasses will get trapped in the heater core.

I've ordered a FoMo Racing rad, along with a 195* higher GPH t-stat , new belt, new cap, and some Amsoil coolant. I'll probably replace the fan clutch while I'm in there since it's not too expensive. No evidence of a head gasket failure. I'll take a gamble on the pump because I just don't see that failing at 40k miles, especially with a welded steel impeller, but who knows. Pretty sure is the t-stat but it gives me an excuse to do some upgrades while in in there. Will post pics when I get everything in.

Your T-stat would have to be sticking in a near closed condition to give you those symptoms. I'm certain they are designed to fail in the full open position. I'd tend to suspect the water pump, but I would not expect the rapid drop in the CHT value you experienced when you stopped to check. When my CHT has gone up (due to towing under load), it's taken quite a while to drop back down.

I think you may have a faulty CHT temp sensor. The ECT is derived from the CHT and if the sensor is sending a "hot" voltage value, you're going to go into failsafe mode (which is what you did). The failsafe CHT value is 258, so the 260 you saw would definitely give those symptoms.

- Jack

Hmmm?
Sounds vaugly familier.
Before you were going to tow.
Did you happen to load the tow tune and then open the custom option menu for the first time?
Any dtc codes?

No DTC's on the truck. I run the 87 tow tune full time, so no changes made there. I didn't play in the custom menu either. Zero issues when not towing. Still waiting on my parts to arrive....

What sounds familiar to you. Are you experiencing the same thing, or have before?