I just got back from about a 700 mile trip with my truck 1998 Ram 5.9. I was pulling an enclosed trailer that weighed probably around 4500 lbs. Spent most of the trip at about 60 mph with OD off. When I left yesterday morning the engine temp was staying right at 180*. Stayed right around there for a few hours then the temp gauge dropped all the way down. I had my scanner in the truck so I hooked it up and it was showing the truck was running about 120-130*. Stopped to get gas and checked over everything and it looked good. Started it up and it went back up to 180* and stayed there until it got dark out last night. Then the temp gauge dropped back down and stayed there. Drove the rest of the way home and the gauge never came up. I'm thinking radiator cap, thermostat, or that the sensor is bad. I did the plenum, tc, hoses, stat, and water pump less than a month ago. Thoughts?

 

Possibly thermostat stuck open. Sounds like the cooling system works pretty well though.....

 

could be, and most likely is, that your 'stat is sticking.. new stat time.. leaving the circulation going full blast (stat not closing) will cause it to over-cool..

the worst thing that will happen to you running an engine too cool (in the short term) is that it will open loop and run off of tables, and dump fuel, causing you to run rich.. which will kill your mileage..

most likely your stat the way you described it.. you implied your temp gun agreed with your dash, and I see you're running a '98- which had but one temp sensor, right? I'd figure it's good.. swap that stat..

 

ninja'd.. by THE ninja.. HeyYou, NINJA!!! :-)

 

Kinda wish I had that problem last week...

 

I don't have a temp gun- was going off what the scanner was showing which would be whatever the computer was reading. Another odd thing is that the scanner also said it was running closed loop. I don't know about mileage because I was only getting about 8-9 pulling the trailer anyway lol. I know I probably should have replaced the temp sensor when doing the plenum but I didn't. Upper and lower hoses both felt good and hot though. I'll go take her out for a drive in a little bit and see what happens today.

 

Well drove down to the store and back. Started out cold went up to 180 and temp dropped a little. Hung out around 175 for a little bit then down to 130. Stayed between 120-140 the rest of the way to the store- about 5 miles. Shut her off got some groceries then headed back home. On the way home it mostly stayed between 160-178 but was fluctuating constantly- reading 158, then 165, then 178, 167, etc. Kind of bouncing around a lot IMO. Dropped down to 130 but then went back up. Would that be normal to bounce around that much? Kind of makes me think it's the sensor.

 

re-read your first post..

you've got a bubble my friend..

burp that rascal good.. air does funny things to cooling systems..

 

Thanks I'll give it a shot

 

Tried burping it again and it seems to have helped. Temp still bounces around some but not as much. I jacked the front pass side up as high as I could and also squeezed the bottom hose some. Should I just keep doing this? Any other tricks to burping it?