Truck:1997 Dodge Ram Sport 4x4 5.9L, currently about 130,000 miles
Background: I've owned this truck since practically new, garage kept and well maintained. Runs fine, never had any major engine work as it hasn't needed it.

Issue: Last winter (sub-zero temps) I actually had an overheat issue. Had only driven 15-20 miles and I noticed gauge climbing. Based on the outside temp, I attributed it to a stuck thermostat and possible air in the system, and thought maybe... water pump...

The truck is not my daily driver and since getting to the thermostat is a bit of a job, I decided to do the following will 'in there':
- New 180 degree thermostat
- New (nos MOPAR) water pump
- New Upper and Lower radiator hoses
- Replaced both temp sensors
- New serpentine belt and (nos MOPAR) tensioner) figured I had it this far apart.
- Flushed the coolant system

When I removed the (original) water pump, the fins were intact and the impeller seemed fine, but the new pump was installed. With everything back in, I added 50:50 coolant mix and a bottle of Water Wetter. I did use a vacuum style coolant refill system to minimize any air in the system. With the radiator cap OFF, after warming up, upper radiator hose was warm, radiator warming up (ie. Thermostat opened) and I could clearly see flow through the visible tubes inside the radiator. This to me was a good indication that the thermostat was opened, and the water pump was doing it's job circulating the coolant.
Radiator cap back on, I let the truck run, keeping an eye on the temp gauge and the truck runs at about or slightly below half gauge (where it normally is). I let it sit for a good 20 minutes (65-70 degree day), temp was stable. Then a couple local trips, no issues and I 'assumed' I was home free.
THEN....
About to take a trip, let the truck warm up, get a 15 miles or so and I notice the gauge going slightly above half gauge. The only thing that I'm thinking,........fan CLUTCH? SO........ I change it. It didn't seem bad, but it was the original, and easy enough to do. So OFF I go. Get on the highway (80 degree day, 65-70 mph), go about 20 miles, ...Once again, ..............temperature creeping over half gauge, even getting to 3/4 gauge, when I pulled over. Truck didn't 'overheat' in the sense of spewing coolant, but it was definitely hot. I let it cool some, started it and temp sat at or below half gauge. Heading back home there were times it would stay about 1/2 gauge, but then others it would climb a bit.
I got home, let it cool, then started it and let it warm up. It sat in driveway running (again, 80 degree day) for a good 20-30 minutes, never went over half gauge.
For the record, the truck runs fine, oil is clean (and no visible signs of coolant, ...ie. head gasket) and even when it was hot there didn't seem to be any visible performance loss.

SO...
The only thing(s) I can think of at this point is either the radiator is restricted some and/or a possible exhaust restriction (ie . converter). Based on no visible performance loss, I am going to order a radiator.

I'm putting this out there in case anyone else has experienced similar and/or for suggestions advice others may have.

Thanks,

Kevin

 

I just wanted to post an update...
Radiator changed and it appears that resolved the issue. Truck is back to running it's normal temp (just below half scale)

For the record, I pulled a vacuum on the coolant system and it held for a good 15-20 minutes, so that was good.
While talking to a friend of mine, he noted he had access to a 'block tester" (I had actually never heard of one). Simple simple test, ...........put blue die in clear cylinder, leaving radiator cap off, let vehicle come up to temp (thermostat open), ...pull VAPOR through blue liquid, in the presence of any CO2, the blue turns to yellow almost immediately. We did the test, repeatedly, vapor bubbles pulled and the fluid stays blue. Noting here (as you would imagine) if you had a cylinder/head leak and combustion gases were getting into coolant, ...you would fail the test.

Anyway, just wanted to post for others who may end up here...


Thanks,
Kevin

 

So you're saying the radiator was clogged so bad that it overheated in minus 0 degrees? How in the world? These engines like to run cool anyway and have a huge open engine cavity. That's quite a story. I wonder if the temp gauge is accurate? And sensors? Seems I've read more 94-97 "overheat" stories over the years than 98-01. Wonder if wires or sensors were changed. . . . Always makes me confused as my truck has never overheated or even wanted to and it's pulled heavy weight in triple digits often.

 

Kevin, That is one beautiful Gen 2. You've done well on maintaining her exterior.....Thanks for the story and remedy!!!!!