I drove up to Tahoe a couple weeks ago and noticed my temperature gauge woudl go up to 180°, stay there a little while and then dive down to 140°. It yo-yoed like this for 5 hours up and 5 hours back.

This makes me nervous. I have had my truck for 8 months and bought it with 200k on the odo. I want to cahnge my thermostat. Should I get one from my local aout store or get a genuine Cummins part? What is the part # and where is the best place to get it?

What kind of collant should I use? Is regular Prestone ok or is there special coolant for diesel engines.

TIA,

Bob

 

Your fluctuation is totally normal

Cummins says,

THE COOLING SYSTEM USED ON THE CUMMINS DIESEL ENGINE EQUIPPED VEHICLES PROVIDES THE CAPACITY AND PROTECTION OF THE HIGHER GVWR AND GCWR RATINGS AVAILABLE ON THESE VEHICLES. OWNERS SHOULD BE ADVISED OF THE NORMAL SLOWER WARM UP AND LOWER ENGINE OPERATING TEMPERATURES ASSOCIATED WITH DIESEL ENGINES.

THE COOLANT TEMPERATURE GAUGE WILL FLUCTUATE ON DIESEL ENGINE EQUIPPED VEHICLES. IT IS INFLUENCED BY VEHICLE LOAD, OUTSIDE AMBIENT TEMPERATURE AND EXTENDED IDLE TIME. THIS FUNCTION IS CONSIDERED NORMAL

 

I think I still want to change the thermostat. I am going on a desert camping trip at the end of the month and a thermostat is cheap insurance. I don't want to get stranded out there.

Waht about coolant? Is regular gasser coolant ok?

 

Insurance is not bought by fixing something that ins't broke. The posibility of a fubar is always present. Get the genuine cummins or Mopar part. Replace antifreeze with the color presently in unit.

 

It is working the way it is suppose to. I think the chances of your new thermostat failing are greater than the old one.. thats always the way when you change something that don't need to be changed. Just make sure your fluid is full with 50/50 mix.

 

I replaced the thermostat with water pump on my 97 3500 with a cummins one last year when my water pump was leaking. The temp gauge used to cycle but now it is more stable. I guess they upgraded the themostat so it won't cycle as much.

If you want piece of mind replace it or buy the cummins one and keep it on hand. Make sure you get them rubber pieces that go in the housing with the tstat. The last NAPA water pump lasted 2 years. Next time I'm getting a cummins water pump. I had no choice on this time around...I had to get it fixed fast. Cummins is 50 miles away and NAPA 5 miles.

 

I got the same basic issue, cold in the morning (0-5 degrees) it runs up to about 205 then drops to 150, after that initial hi temp it runs up to about 190 then back to 150 and keeps up the same cycle for the 35 mile drive in. It's only got about 2K on the water pump and T-stat. I will be replacing my radiator this weekend tho, and making a "snow shield" to go under it. Plowing constantly I end up with a 6"-8" thick pack of ice and snow under the bottom of the radiator and the bottom is starting to get a bit soft. Last thing I need is that 30# pack of ice breaking free and taking 1/4 of my radiator with it.