Engine/Transmission (1998.5 - 2002) Motor Temps. fluctuateing

[broncojohn]

More recently the coolant temp in my truck is fluctuating where it will cycle a little above 190, then will go back to the normal area, right below 190. It starts to do this when the truck is completely warmed up. The temp will go start to climb to a tad bit over the 190 mark and holds there for about 30-45 seconds, then goes back down to a little below 190. I just didnt think this was normal, is it normal for the temp gauge to be so sensitive? The coolant reservoir is full, actualy its a little above the "Add" level mark and the radiator is completely full. At the beginning of the summer I put in a new water pump. Could it be the thermostat? Thanks in advance.

 

[AKAMAC]

The t-stat is probably sticking and showing it's age. Mine does the exact opposite, it goes from 190° to 160° on cold mornings driving down the freeway. The high temp is a bad thing, try swaping it out, easy R&R. Be sure to price it out using your local Cummins Dealer as a reference point. Mike

 

[broncojohn]

Thats what I was thinking, it doesnt barely go over 190 degrees. I only have 75k on the truck. Is this commen for t-stats to go up this low of mileage? Also, its kinda strange, I was driving tonight with cruise control on going 60 and the temp stayed normal right below 190 like it normally is, what could be the deal with that? Thanks for your help akamac.

 

[Cummins724]

It could be going bad & only sticking sometimes. Also... the radiator can be plugged up & restricting heat exchange. I had to take mine out & pressure wash it.

 

[broncojohn]

Yeah, I am going to start priceing out thermostats. Advance auto parts has a 190 degree t-stat for 20. 00 dollars, would you all go with this or should I go to the local DC dealership and get a price quote? If it turns out to be the radiator, is it a pain to take them out in these trucks? I have done it in a 1999 chevy suburban with a 350 but not in my truck yet. Thanks for all your help.

 

[FDNYMOPARGUY]

I just went through this. My thread is a few below this one under "winter front". Check it out. It might solve your problem.

 

[Cummins724]

Yeah, I am going to start priceing out thermostats. Advance auto parts has a 190 degree t-stat for 20. 00 dollars, would you all go with this or should I go to the local DC dealership and get a price quote? If it turns out to be the radiator, is it a pain to take them out in these trucks? I have done it in a 1999 chevy suburban with a 350 but not in my truck yet. Thanks for all your help.

They aren't to bad..... the coolant & windshield bottles pull up out of the way & some bolts & clips..... then it is easy.