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Old 08-06-2022, 09:08 PM   #1
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Thumbs up 2006 Cummins ISL Temp fluctuations

2007 Monaco Dynasty TAG 42' side radiator.
Now pass this off to senor moment and maybe engine temp has been fluctuating 15deg has always happened over the years I have been driving the rig but...
last spring I was climbing up I25 towards Santa Fe and notice the temp had gone over 210, stopped to let it cool down and noticed the expansion tank was hissing at some joint and the coolant was boiling.
Made it back to Colorado, bought a new metal tank. NOW..
Climbing up I25 from Colorado into Wyoming I am watching the temp.

It goes up and down with the hills, about a 15 degree range. 194 degrees on the flat and down and up to 208 on the up. I dont remember ever seeing this, or this old guy never noticed.

Reading here, many threads, Thermostat or Temp sensor. The Boiling coolant could have ruined the thermostat, my first though. The Temp sensor for $19 on AMazon, so why not.

ANYTHING ELSE? I bow to you , the knowledge base
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Old 08-07-2022, 08:22 AM   #2
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I downloaded a copy of you operating manual from here https://www.monacocoach.com/service-...pairs/#manuals
on page 273 it describes the cooling system. Your fan speed is controlled by a Fan Drive Controller, mounted on the main rail near the fan.



Based on the description it states that your coolant temps will range between 185F up to 210F. The controller will start ramping up fan speed at 185 until temps reach 195, at which point the fan is running WAO but the engine temps can reach 210. So it sounds like your system is working as it should.

My system is similar except it uses a Thermovalve to control fan speed. Many people change out the Fan Drive Controller to a thermovalve as the controller does have a tendency to fail, especially if the fan controller is mounted were the wires are pointed up, water wicks into the controller.
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Old 08-08-2022, 07:26 AM   #3
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Great info, thanks for that.
I made a run from Buffalo WY to Montana yesterday and that is exactly the way it ran. Seemed to run at 194-5* on the flat 199 up the hills and 204 on the steeps. So I guess I won't worry.
Thanks again
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Old 08-08-2022, 07:30 AM   #4
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Oh, I do have the electronic fan controller and I did verify this spring that unplugging it sent the fan off at full speed.
I may change out the temp sensor and thermostat anyway, what the heck. I'll go off the cummins today and get what the database has for p/ns.
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Old 08-08-2022, 11:38 AM   #5
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194F on the flat seems a little high, at that temp the fan should be running WAO. What were the outside temps? Seems like based on the description in the manual yours should run ~183F, anything higher and the fan should start running faster.



Mine runs 183F on the flat, but I have an ISC.



Where are you getting your temp readings from?
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Old 08-08-2022, 12:41 PM   #6
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To answer your question, I read the temp on both the gauge and the Aladdin engine info page that shows engine and tranny info. Which I assume it gets from the ECU

I understand it the manual is a bit broken up on the subject but it does say in different paragraphs
"When coolant temperature rises above 185º F, the fan drive controller slowly closes off the bypassing hydraulic fluid from the switching valve" this is to start the fan spinning. That coincides with the fact that the thermostat is set to open at 185º F.
"As coolant temperature rises, a spool valve begins to move in the switching
valve....higher the coolant temperature, the further the spool valve " the fan goes faster.
"approximately 195º F, the Fan Drive Controller begins to restrict fluid flow. The restricted hydraulic fluid pressure then begins to move the internal spool valve of the switching valve. This process will continue until coolant temperature inside the radiator reaches approximately 210º F. At this temperature hydraulic fluid flow through the Fan Drive Controller is stopped" This is wide open and the fan should be running at full speed.
That is the way I read it.
It also mentions the speed of the fan takes into account the engine RPM.

So who knows, but what I experienced yesterday kind of follows what this says.
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Old 08-08-2022, 01:02 PM   #7
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OK, mine is a little different but it does sound/read like yours is working as designed.



I use a Silverleaf VMSpc to monitor my engine and transmission. I hardly look at my dash gauges anymore.
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Old 08-09-2022, 07:49 AM   #8
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My ISC has always fluctuated from 185 - 210 on hot days.
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Old 08-09-2022, 08:02 AM   #9
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Quote:
Originally Posted by e4services View Post
Great info, thanks for that.
I made a run from Buffalo WY to Montana yesterday and that is exactly the way it ran. Seemed to run at 194-5* on the flat 199 up the hills and 204 on the steeps. So I guess I won't worry.
Thanks again
My 400 ISL ran just like that in my 07 Itasca Ellipse.
My new 450ISL almost the same, it runs slightly hotter, the secondary fan kicks in at 208-210

I did that Buffalo, Wy to Montana on I 90 I ran about the same
That is a long up hill grade going west, less so going east.
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