Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 06, 2025 ...

If you have an IR gun, use it to check temperature at the thermostat housing.

That will help you determine if this is a temperature or gauge issue.

So curious. Are the radiator fans running hiwhen cold. If you disconnect the plug on the controller they should ramp up to max speed cold

Hydraulic fan controller DIY

While I completely agree that running the fan on high is not desirable from a HP, MPG, noise and dust standpoint, unless the thermostat (or alternate plumbing) sends coolant to the radiator, the amount of air passing through the radiator should not be a big factor in coolant temperature in the engine.

The fan may also be turned on for some speed with the AC compressor. AC should also be called for with defrost.

The A/C condenser is on the other side and has it's own fan. The controller is monitoring coolant and intake temperature.

Yes, another way to look at cooling through the radiator:

Engine temperature should be the same with fan on high or low (unless under high load when it may rise somewhat).

Engine temperature should be the same if 20 degrees F or 100 degrees F (unless high load when it may rise somewhat).

Fan speed and ambient temperatures should not impact coolant temperature.  Extreme example is Ice Road Truckers who often drove in -20 degrees F.  Their engine temperatures were as they should be.

So why do they cover the radiator?

I setup a new fan controller to replace the Sauer-Danfoss FDCA controller that failed. The fans are working great now. I set the fan on/off temperatures to the chart in , page 483.

The first chart is where I was loading the engine up by holding the brakes with it in gear to get some heat into it. The green line is the temperature from the engine ECM, the blue line is from the fan controller. The sensor for the fan controller is farther back in the side of the block. The engine ECM reads the temperature at the thermostat housing. 100% fan, means the command is 100% and the fan is off since the solenoid is normally open, it needs current to close and stop the fan.

Second chart is at high idle with the A/C running to get a little more load on the engine. You can see the temperature climb and the fan ramp up and down to match it. It looks like it's working pretty well.

Last picture is the controller installed where the original one was. I need to work on the mounting bracket a little more, but it worked for testing.

This with the new thermostat should fix my over cooling issue.

There is also a TSB from Cummins on the over cooling issue where the thermostats can stick open.
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I'm having some issues with my 2004. I took it out last weekend and went to New Symrna Beach in Florida. Temperature was 20°F ish when we left Atlanta and didn't warm up much till we were well into Florida. The coolant temperature never got warm. I was cruising on the interstate at 75 mph, with a toad and the engine temp was barely 100°F. I also had very little heat from the dash. The transmission temperature was also very cold. The gauges, and two digital displays all matched temperatures. On the way back, I had ~175°F coolant temperature for half the trip, then it dropped for the second half.
So I figured the thermostat was stuck and I'd replace it when I got home.
I just replaced it today and it's still having the same issue. The original thermostat was not stuck, I checked it with some hot water and it worked fine. I did a stall test and held the engine at full power against the brakes and the engine warmed up very slowly then cooled back down.
The radiator hose coming out of the thermostat housing is warm, and I wasn't expecting that to have coolant flowing until it warmed up.
Does anyone have a diagram of how this is plumbed up? Or any suggestions? Is there another valve somewhere that should be closing? Thanks.

Just crossed into Arizona from Georgia on our way to Mexico to get the 2004 painted and the fan controller is working great. I added in the Retarder Temperature that the transmission is reporting and I have the fan set to ramp up if that gets warm too. Coolant temp and Intake temps have been right where they should be for the whole trip.  If anyone needs any more information on this setup, or help setting something like this up on theirs, just let me know.

I have noticed that under odd circumstances you can exceed IAT and having it being monitored is a good thing.

So for a Cummins M-11/ISM, what is the acceptable temperature range.  Input Air Temperature is one of the parameters that I monitor but I have never seen posted what that temperature should be.  I generally see an IAT of about 20 degrees above ambient air temperature.