temp guage goes up and down alot....

[MBurke]

Hello... . I am very new to this forum, and so far I have learned alot. I noticed today while drivng my (new to me) 97 3500 on the interstate for the first time, that my temp seems to go from about 140 to 190, then rapidly falls back until it hits 190 again. It does this very often. Is this normal, or do I get to buy another part??? In a stretch of 5 miles, it may do this 4 or 5 times.

 

[LandShark]

Yea. This is normal. There is a new design thermostat that doesn't vary quite so bad if it really bothers you. Dodge says it's not a problem!

 

[Deezul1]

Be thankful, your truck is normal. These trucks run so cool that what you are seeing is the thermostat cycling, opens at 190 to let the water through the radiator which cools it down to 140 and the stat closes. It doesnt hurt a thing and lets you know the cooling systems works real good.

 

[Eric_77]

It starts to settle down after 150k miles and by 200k it is almost rock steady. At least that is what mine did. I see some variation on real cold days but it seems to find about 170 and hold even then.

 

[SOOT]

Temp guage

It's normal. My does the same thing and has 130k on the clock. so don't worry about.

 

[TurbogRAMpa]

Well I was going to ask this same question. My 96 with 190k does this all the time. Boy am I smiling to hear that it is not a problem.

 

[SRehberg]

temperature guage moves a lot

I too experience the problem of cycling of the temp guage and was also told this is normal. I took it one step farther by contacting the authorized Cummins dealer (big rigs) and was told these engines in industrial applications had a modification done to them to keep the temp rock solid. It's a little different at the thermostat neck than ours though. He states the quick cycling of the temp is not good for the head etc. as the expansion/contraction causes stresses that are not normal for these engines. How true I don't know, but by the mileage you guys have without incident, it does seem to be o. k. so far. DC says the reason it runs like this, is due to the oversize radiator used for the diesel, that is also used for the V10 and provides more cooling then necessary. My 2cents worth.



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'96 2wd auto (sometimes)

 

[Joe G.]

I really have a hard time believing that the small fluctuation in coolant temp we are seeing on our gauges will affect anything. I see at most a 40 degree cycle in cold weather. The warmer the weather temp the smaller the cycle. Now this is coolant temp, not iron temp so I don't think the temp of the metal swings that much. I rather doubt that the iron drops quite that much in temp. At the same time the temp variation for iron close to the combustion chambers must vary a LOT more than 40 degrees just running up and down hills. Especially with a load. There are a lot of these trucks running around with a LOT of miles on them and have had no problems than can be traced to the temp cycle of the coolant. I have heard of rumors that someone heard from someone who knows a Cummins expert etc etc. My truck has over 171K miles on it and still has the factory stat.

 

[KYOUNG]

temp gage

I just changed to my 4th thermostat last week. the first two fluctuated as everyone has noticed. the third one stuck open after 2k,so i replaced it with anew one from southern plains and it appears to be rock solid ,no temperature change

 

[SRehberg]

temerature swings

My earlier reply about the stresses to the engine was information related to me by someone who does this for a living, and you know yourself, the injection of water 40deg. one way or the other quickly can't be good. Other mfg's seem to be able to control the temp to a reasonable level without all large swings, so I think Cummins/Dodge could come up with a good solution.



Don't get me wrong, I AM glad the temp swings seem to be harmless from what you are reporting, but I still don't like the speed at which it occurs. Temperature changes pulling, or climbing hills occur slowly, not in a matter of seconds like the thermostat allows. There's got to be a better design, as the industrial engines (same one) are not suffering from this malady.