Engine/Transmission (1998.5 - 2002) Engine Overheating

[Bratton]

I was towing a light trailer (3500 lbs) on flat interstate this weekend when the truck all of a sudden started surging. I looked down at the gages and all was normal initially but then the temperature gage shot up from normal to pegged in a span of seconds. The fueling also immediately was reduced (I think by the computer) so all the engine would do is idle. I immediately pulled over and popped the hood. Nothing looked out of the ordinary and nothing felt hot. After about 15 minutes, I popped the radiator cap and as I couldn't feel much warmth coming from it I touched the coolant and was surprised to find that it was only lukewarm.

As the engine didn't feel hot and the turbohousing was also cool to the touch, I restarted and limped into the next town at idle.



It seems like it could be the thermostat, but I don't see why the engine would have started acting up before the temperature gage moved up.



I've not seen any other threads that show a problem like this. Has anyone out there experienced something like it? The dealer is going to look at it later on today but it has taken them multiple diagnoses in the past before getting it right so I'd sure like to know some of the other theories!



Thanks!

Bratton

 

[bmoeller]

Limp mode? Sounds like it could be the thermostat sticking shut.

 

[Bratton]

Looks like it stumped this board too!



The dealer plugged in the scan tool and basically was finding just about every code you can think of was set. The computer was convinced that the engine was falling apart. Fortunately, the problem is actually the ECM itself. They will put in a brand new computer when it gets here in a couple of days.



Bratton

 

[Dane]

Be very wary of what the dealer says. Sounds like a sticking thermostat to me too...

 

[Bratton]

I'm half inclined to believe the dealer's diagnosis because the surging started before the temperature gage jumped. However, since the coolant in the radiator was only lukewarm to the touch, that does concern me that maybe coolant was not circulating properly through the engine. The truck had been running at 80+ miles per hour for about 15 minutes when the malfunction started so you would think the coolant would have been hotter than that.



On another topic, I have always been disappointed with the mileage on this truck as I seem to average about 13 and get about 15 at best on the highway. I'm hoping that a new computer might help in this area. My old 1993 averaged closer to 18 and it weighed within 200 lbs of this one and I have a hard time believing that it was more aerodynamic!

 

[pgasch]

Truck fixed?

Did your truck get resolved? My 2001 Dodge ram has same problem. ECT gauge pegs in seconds but truck is NOT overheating. Runs terrible and throws many codes.

 

[Sticks]

In the grand schene of things, thermostats are cheap. After 5 minutes of 80 mph driving with a trailer, the engine is gonna' be HOT Replace that thermostat.

 

[WestTN]

I believe the water pump has failed. Thermostats are designed to fail open, so that would not cause the engine to overheat. If coolant flow stops the engine will quickly overheat.

 

[Todd T]

A couple things here. First; these trucks have huge rads and extra cooling capacity in reserves. I would tend to believe if you were lightly towing on flat ground in 50-60 degree weather @80MPH (dont leave out wind chill) the chances are you ARE cycling the thermostat and the rad water was only luke warm. The thermostat opens at 190. In cool weather you can watch it cycle. It will heat up to 190 and you will see a 20-30 drop and repeat.



On the mileage, depending on how long the ECM has been bad you may see a gain in mileage.