Thermostat Troubles

[MBlanks]

Back in the summer, I replaced the original factory thermostat on my truck because it was running way too cold, as in it would never warm up enough to get into the normal operating range. I replaced it with a thermostat from NAPA, but the new one didn't have the "jiggle pins" that you are supposed to line up, according the the manual. After installation, my temperature has been swinging back and forth. The temp will peak out slowly on the third notch of the normal operation range on the temperature gauge, then swing all the way back to the second notch in about 2 seconds. It will continue to do this for the entire time the truck is driven.



My first thought was that the thermostat wasn't opening at the correct temperature, or was sticking, does anyone have a clue about this?



Mark

 

[Tim1]

Toss the napa and replace with the cummins Pn#3802968 @ 26. 00 as it is a better thermostat. That number is for a 92 and may be the same for you. Tim

 

[JLEONARD]

Are you 100% positive that you got ALL the air out of the system?

I'd go thru that excercise again if I were you... . if that doesn't work then try the Cummins part.

Jay

 

[paccool]

I tried a NAPA thermostat last year and had a bad overheating problem when towing the travel trailer. I was on a trip, stopped by a Cummins dealer and got a new thermostat from them, replaced it and that took care of the overheating problem.



The NAPA one was more like a car thermostat and I think it was allowing water to bypass even when open. There is a small hole in the block behind the thermosat that allows water to bypass when the truck is cold. When the thermosat opens, this gets plugged off. It also has a smaller opening for the circulating water to go thru.

 

[michigandon]

Found this number over at the Diesel Truck Resouce:



Updated Thermostat for 89-93 models

Cummins Part# 3802273



Anyone have any comments or experience with this stat? I replaced the original with this one prior to installing the engine in my coach, but I haven't yet ran the engine so I cannot comment on how well it regulates the coolant flow/tamp.

 

[bgilbert]

MIDon, a couple years back, I searched the archives and posted questions etc, well I cant remember everything but the t-stat that i bought is pn 3802968. Havent had any problems with it, no fluctuations. The t-stat that I replaced was the original cummins pn 3915908. Still have it, some day I'll test it on the stove.



Also read that alot of 1st gen CTD owners were having problems with the napa t-stat. So like Tim1 said trash the napa t-stat and buy a cummins t-stat. I havent had the temp fluctuations with it. Same with napa fan clutches-stay away! Bill

 

[MBlanks]

Thanks guys for your input, I'm going to run down to the local Cummins shop and pick up a new thermostat. I will let you know how it works out. I'm used to having good luck with NAPA parts, but that was before I owned a CTD. Now I think I am going to have to get used to using Cummins parts instead of the el cheapos. Once again, thanks for your help.



Mark