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Old 10-26-2014, 07:23 AM   #29
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I had no idea there was that big of a variance in temps with Cummins. My 2000 Dutch Star w/ISC and side radiator is rock solid at 180 on flat ground. When climbing it'll start creaping up. When it does I'll just down shift it to keep RPM's at 1800-2000, and the temps will come right back down to 180.

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Old 10-26-2014, 07:14 PM   #30
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like yours my '97 London aire stays about 180-185 and on hill creeps up but never 200 yet...tranny temp is always below 200.. I think older coaches are not like the new ones for temps..mine has been upped from 300hp to 350 and has a pyro and boost gauge.. at level no wind about 3.5-4.5 boost and on hills goes to 22 before downshift. and pyro temps not above 1090.. and last trip last week averaged 9.6mpg from bis nd to Denver co then black hills and home..i thought decent,, jeff

2007 Alfa Gold!! model 1008. 400hp Freightliner, IFS!!
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Old 10-26-2014, 07:20 PM   #31
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Cummins Water temperature

I have an ISM 500 that does the same thing, 170-205 flat ground ,Kinda drives me nuts trying to figure it out. Good to know I am not the only one.
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Old 10-27-2014, 06:46 AM   #32
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A fellow traveller ??

Originally Posted by Tireman1 View Post
I have an ISM 500 that does the same thing, 170-205 flat ground ,Kinda drives me nuts trying to figure it out. Good to know I am not the only one.

Anyone else out there with the same situation?? Especially anyone who figured out what the heck is going on here????
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Old 10-27-2014, 11:44 AM   #33
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Mine does something similar: '96 Cummins 8.3. both analog temp gauges behave themselves below 200deg (indicated). If outside air temp is 80deg+ and I climb a hill so that the engine temp goes up, at about 200deg the water temp gauge takes off and suddenly reads about 240deg. The trans temp gauge may have gone up only 5 or 10deg concurrently.
After bringing the engine temp down slightly by down-shifting, the water temp gauge will suddenly drop to about 180deg.
I suspect a faulty water temp sender. Anyone care to comment? Am I correct, or is there something else going on here?
Andy Clark
95 Beaver Patriot 37
Cummins 8.3C
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Old 11-16-2014, 07:59 AM   #34
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Your cooling system is working as it should if / when you see variations. They all work the same .... as your thermostat opens ... the engine temp will cool down. As it closes ... the temps will climb a bit ... this occurs to allow the coolant to cool down by being held in the radiator. As the temps come up (engine temp) the thermostat will reopen allowing the cooler coolant into the engine. When temps reach (overall) the temp where the fan(s) kick on .... the temps will come down to the point where the fan(s) will shut down.
The point is ... the variance in temps is an assurance you cooling system is working properly .....
additionally, engine RMPs will cause some change in temps as well, how much coolant is being pushed through the system by the water pump .... thus the reason cooler temps when down shifting on hills .....
Its when you don't see this happening should you be looking into a possible problem with the system ...........
This would apply to any cooling system.... gas, diesel, coach, car, truck, etc.

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