ISL 'normal' operating temp

[smlranger]

This is my first Cummins (had a CAT in previous coach). The pesky, expensive, prone-to-failure, Sauer-Danfoss hydraulic fan control gizmo on my rig is likely failed and my side radiator fan runs constantly at high speed. Some folks say fine since some ISL's tend to run hot due to variations in how some coach builders install cooling components, etc. The other school of thought is with fan running all the time, my engine may tend to run cooler than needed for optimum efficiency.

I cannot find specs on what is optimal operating temp for the ISL 425 clean diesel engine. Today, pulling my CRV on a short, one hour trip in 70F ambient temps, my Silverleaf shows an average temp of 188 - 192 with a brief period of 195 when climbing a short grade.

Is this generally too cool for the ISL or about right?

[wolfe10]

With the system functioning properly, you will have a distinct temperature RANGE.

First is the thermostatically controlled temperature. With fan speed on low, this is the "rock solid" temperature except under heavy loads/high ambient temperatures.

Once the thermostat is wide open, there will (and should) be a 5-10 degree increase before the fan controller goes to high. If it went to high at or very close to the thermostatically controlled temperature, you would waste a lot of fuel and HP turning that fan on high more than necessary.

Then once the temperature reaches the trigger point for high fan speed, that is exactly what happens.

Very similar to what happens with air pressure with it cycling between cut-in and cut-out PSI.

Brett

[mytime]

Blaster Man wrote:

racerchaser wrote:
...My fan kicks in at 210 and the temp goes to 180 and then starts back up when the fan stops...

How can you tell when the fan comes on and goes off?

The silverleaf will show a variance in the Temp., usually when pulling a grade you will see the temp rise to maybe 210-215 and then start dropping back, depending how steep and how long the grade is..,and at some point the temp will appear in large print on the Silverleaf, don't know exactly what temp, I think I was near 220 when it appeared, long steep grade, but did not go any higher.
With all that said, you can also control your temp by using the proper gear to handle the grade, keeping the RPM at the correct setting, I go around 2,000 or a little above, that will keep the temp in check also, never let the engine get behind the curve.

[mytime]

Mr.Mark wrote:

Blaster Man wrote:
My ISL runs around the high 190s. Hotest it ever got was crossing the Rockies...207.

Mine is about the same on running and climbing temps.

MM.

Mine too..Marvin
PS: I would definitely check everything before changing the Controller!! Suppose to be a couple of sensors located in the system somewhere. And My Controller is different than yours, mine is located on the frame in the lower left by the radiator., but the temp. settings are regulated by the ECM on my coach, there are a varity of positions that you can choose(different settings for each speed, when it probes the fan to change speeds). Yours may be different. Not all shops are created equal, you may have to call Kevin Waite.

[Blaster_Man]

racerchaser wrote:
...My fan kicks in at 210 and the temp goes to 180 and then starts back up when the fan stops...

How can you tell when the fan comes on and goes off?

[JimM68]

As was said, the thermostat keeps the engine temps where they belong, assuming proper cooling efficiency.

The fan controller systems job is to maintain optimum cooling efficiency.
Yours, being stuck on high, is not being it's most efficient, but overall the system is cooling properly.

Did that make sense?

[racerchaser]

When you say "clean diesel" I assume you use ULSD fuel. If so, you have the same engine I do, an EPA07 425. Your temp look about normal for the conditions. This engine is designed to run hotter than previous engines for EPA requirements. Out west this summer, with 80 deg temps I routinely saw 200 - 214. My fan kicks in at 210 and the temp goes to 180 and then starts back up when the fan stops. I am now used to temps from 180 to 214 depending on temp, altitude, wind, grade, etc. After five years I have just gotten used to it.

[Mr_Mark1]

Blaster Man wrote:
My ISL runs around the high 190s. Hotest it ever got was crossing the Rockies...207.

Mine is about the same on running and climbing temps.

MM.

[siggyd777]

Your temperature numbers look very normal,just like my ISL 400.
Siggy

[smlranger]

Thanks for the tips and feedback.

I can easily locate the fan controller fuse and it is good. I sent the following pic of the gizmo attached to my fan motor to a Sauer-Danfoss distributor Sun Source. They contacted Danfoss and have now informed me that this device is made by Bosch-Rexroth. Sun Source does not distribute for Bosch. I've Googled for this gizmo under Bosch and Bosch-Rexroth with no luck. Country Coach will be my last resort since they are really fond of their parts.

[mmccwill]

The fan controller defaults to high speed when you lose the 12v or ground -- Bill Willard

[mmccwill]

Check the 12v fuse going to the controller -- If it`s blown, the fan will run on high speed -- You will probably have a hard time finding the fuse -- The best way to check, is disconnect the connector at the controller, & check for 12v power there -- Bill Willard

[wolfe10]

Extra HP and better MPG and less fan noise are reasons that you may want to get your two speed/variable speed fan controller fixed.

[smlranger]

wolfe10 wrote:
Fan on high will NOT cause the engine to run too cold. The thermostat determines how much coolant goes to the radiator. Very similar to operating in near-freezing temperatures-- the thermostat doesn't put as much coolant to the radiator.

Yes, fan speed on high will lower temperature of coolant in the radiator AND take extra HP.

Thanks for that clarification/reminder. I will not fret the failed fan controller. Can't find anyone who has one anyway and I am told the Sauer-Danfoss controllers many coach manufacturers use fail often.

[wolfe10]

Fan on high will NOT cause the engine to run too cold. The thermostat determines how much coolant goes to the radiator. Very similar to operating in near-freezing temperatures-- the thermostat doesn't put as much coolant to the radiator.

Yes, fan speed on high will lower temperature of coolant in the radiator AND take extra HP.