Thermostat Problems
 

Any one having trouble with your thermostats sticking? Mine will heat up to 190 deg. and in about 2-3 seconds it will be at 140 deg. If I put another thermostat in it will be the 3rd one in 2 years with this same problem. :humm: I'm at a loss.

They had a bad bunch of them out n about. Where are you buying them, if I may ask?

Mine needs to be replaced tool... Just wish I had time to do it.

One at oreily's and one at dodge. I guess this one i'll try toget directly from cummins.. I just didn't know if there may have be a problem somewhere else causing the thermostat to fail. I put a canvas feed sack with a 4-5 inch hole to block some air thinking it may help.. but it didn't..

My stock one went about 18 months before it decided to conk out. New one from Cummins was $25. Some say it's too much, but if it decides a warranty, it's worth it.

Mine does the same thing. I put a new one in lats week when I swapped radiators and it still does it:argh: I asked my buddy about it and he saiid maybe air pockets in the coolant somewhere? The heater core is bad maybe thats what my problem is.:humm:

Get the thermostat from Cummins - they cost a bit more but you wont have any trouble.

You can lose an engine because of a thermostat - and thats a big enough reason for me to spend a few more bucks and get it from ma Cummins.

Thermostat p/n: 3928499
Thermostat sealing rings p/n: 3925466 & 3927305

I have one from Napa that does the same thing. Heats up to 185ish, then drops right above the minimum operating temp line. I figured it was normal. Also runs about 170. Do lower temp thermostats even exist for these? Or are they all 190 and mine is just jacked up?

mine did same thing, got one from o-reallys and it opened once and stayed open. got next one from dodge. besides having a mopar sticker over the cummins label on bag they told me the part was updated recently for these kinds of concern. dont know if you would save money going to cummins vs dealer. i think i paid around $35 that included one o-ring and 2-bigger step seals.

190-195, helps with fuel combustion I think. :humm:

not that i looked very long but can you get 190-195 thermostats for 12vers. i know the 24v calls for one of these but cant be used. i agree with you a hotter stat would help combustion and power and also heater

i have the same problem as well im going to try and get one from cummins and see if that makes a difference

All of them do this. Cummins Thermostat #3934373 will eliminate the fluctuation, but it takes longer for the engine to warm up and the operating temperature is lower than normal. I just live with the needle bouncing around.

all of them do what??? a slight temp fluctuation can be normal but i think most of us have observed a condition where the therm seems to be stuck open or opening way too soon but so far...2 weeks and counting the stat i bought from dodge dont know part# but was in a cummins package has been working ok. i seem to remember something about the rubber coating on the back side coming apart and making the stat more sensitive to temp and this concern has been resolved with an updated part some time ago.

the only problem im really having is it takes to long for the thing to pop and once it does than everything is fine, ive seen it hit the hash mark between the 190 and the 230 before it opens

Mine gets around 210 before it opens and hovers around 190 fully warmed up. It does take a while to warm up, as mentioned earlier.

oh ok i wasnt quit sure to be worried or not since i just spent $2800 on a new fully loaded head with studs

Dodge TSB...

Date: Jul. 7, 1994

Models: 1994 - 2001 (BR/BE) Ram Truck

NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A 5.9L CUMMINS DIESEL ENGINE.

Symptom/Condition:

The vehicle nay not warm completely, especially in cold ambient temperatures. This condition may be due to a thermostat that is stuck in the partial open position by debris in the cooling system.

NOTE: 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

GAUGE FLUCTUATION WILL BE NOTICED MOST OFTEN UNDER STEADY STATE (HIGHWAY) DRIVING USING THIS THERMOSTAT (P/N 4796869). PLEASE ENSURE THAT YOUR CUSTOMER IS AWARE OF THIS NOTE PRIOR TO RELEASING THE VEHICLE.


read more about it here...
TSB 07-07-94

Gauge fluctuation driving down the highway isn't normal BTW.

than what would it be

You got a bad t-stat. Mine quit after I stuck a new one in, from Cummins no less.

My last post up there is the Technical Service Bulletin from Dodge, stating that the fluctuation is normal after installing the new thermostat.

ok i think everyone can deal with fluctuations in the temp guage but as the first post states 190 to 140degrees. i would definately not consider that "normal fluctuation" nor will i accept that as being normal.

mine keeps going to the line between 190 and 230 for about 2-3 minutes then goes back down to normal, using a IR temp gun the radiator is a tad over 170 when that happens

That's correct. it climbs to 190 and then hits rock bottom (the guage shows no temp at all) I mean it's almost as if the key was shut off to that one single guage. however it's just a couple minutes later, it'll start climbing again. It's leveled off now though. it seems to be acting like normal, and I never touched the thing.. I've about decided that there was a piece of trash causing the problem..

Has the coolant system ever been flushed??

i have my radiator completely blocked with cardboard for the winter

If you suspected a piece of something, I'd maybe take a look and see what is was?? :humm:

yeah, the motor was rebuilt 10000 miles ago, and all was flushed then.. I can't think of what else it may have been??

Maybe a piece of gasket material or RTV clogging the thermostat or temperature sensor? It's about time to do another flush on the system since you've already got 10k on the rebuild. I run Evans NPG Waterless Coolant. It's over $30 a gallon, but well worth it in my opinion. Especially for the hot Texas summers. A trucker friend of mine recommended it to me and he's got over 2 million miles on his truck. My girlfriend's dad has a small trucking company and his 3 trucks are now on Evans as well.

Mine does the same thing temp goes to 190 for several seconds then drops to 140, will soon get a thermostat from Cummins:argh:

i havent been worried about mine to much yet but as soon as i get my work bench of cummins parts installed ill get a t-stat from cummins

i have been told this is normal. Normal fluctuation is 60* on the cooling system. if it is 20* out side my truck will climb to about 220* then down to about 160* until it fully warms up then is changes very lil like 20* had someone from cummins tell me this is acceptable. i am not saying your truck is fine but i am not saying its not. Just letting you know what i have been told.

I still have the factory one in my with 241,xxx miles. the first time it opens is around 220 to 230 then drops to about 150. then back and forth from 150 to 190

For some reason right after I bought a new one the one I have it it started working normally... So i've got a spare if it starts acting up again.. Thanks to all for your help!:c:

NOw, for some reason I remember seeing a post where a little piece of rubber worked its way into the thermostat mechanism and prevented the thing from opening and closing. Sometimes, you got to r&r it to see whats happening.

Glad you got it fixed - got to love things that fix themselves.

x2:U:

x3, also if you look at the cummins or mopar thermostat the inside part is lined with a rubber like coating. this coating was breaking down and flaking off. good chance thats where rubber came from. the rubber is there to try to make the stat not be so sensitive. so that can also contribute to fluctuation if gone. btw the newer design still uses the rubber coating but updated to prevent material from flaking off.

Yes, thats what I was talking about - been a long time since Ive seen it though.

well I got my $42 thermostat and gaskets Friday but after doing some searching I see that they gave me the old style thermostat, should I go ahead and install it or return it and get the newer style?
http://img301.imageshack.us/img301/3576/1234050wo9.jpghttp://img150.imageshack.us/img150/4051/1234051mz1.jpg:humm: