Community Forums

MDPD · 08-10-2012, 10:39 AM

We recently bought a 2009 Winnebago Tour with the 400 ISL. Since purchasing the motorhome, the temperature has fluctuated between 195 and 210 degrees, cycling approximately every 5 minutes. The Cummins dealer has replaced the thermostat, tested the fan and gone through everything in the cooling system but the fluctuation remains. On the last visit the mechanic rode with the computer attached and discovered that the fan cycles on at 210 degrees and then disengages at 195 which is obviously the cause of the fluctuation. The repair shop contacted Cummins with the test results and they stated that all downloaded functions are within "established parameters" and that this engine is designed to run hotter due to emissions.

Is this the norm that you other 400 ISL have seen or are they blowing smoke, so to speak? I have had Cummins in other motorhomes and have never seen such a major fluctuation in temperature. Thanks in advance for your comments.

Route 66 · 08-10-2012, 10:44 AM

My ISL 400 temps were similar.

RickO · 08-10-2012, 10:48 AM

My ISL400 will run between 185 and 195 at highway cruise. Pulling a big grade it gets up toward 210 and I have to downshift to keep the RPM around 2K. But, mine is prior to DEF.

Rick

Steve Ownby · 08-10-2012, 11:38 AM

Quote:

Originally Posted by MDPD

We recently bought a 2009 Winnebago Tour with the 400 ISL. Since purchasing the motorhome, the temperature has fluctuated between 195 and 210 degrees, cycling approximately every 5 minutes. The Cummins dealer has replaced the thermostat, tested the fan and gone through everything in the cooling system but the fluctuation remains. On the last visit the mechanic rode with the computer attached and discovered that the fan cycles on at 210 degrees and then disengages at 195 which is obviously the cause of the fluctuation. The repair shop contacted Cummins with the test results and they stated that all downloaded functions are within "established parameters" and that this engine is designed to run hotter due to emissions.

Is this the norm that you other 400 ISL have seen or are they blowing smoke, so to speak? I have had Cummins in other motorhomes and have never seen such a major fluctuation in temperature. Thanks in advance for your comments.

Regardless of the "within parameters" is techno speak for "we don't want to fool with you". It probably is within Cummins temp parameters but it should not be cycling like it is. While it is true, the operation temps have increased with each level of emissions gear, this repeating fluctuation is not normal. And 210 is not a temp you should be seeing in a level cruise situation. You contacted the wrong people. Cummins did not provide the cooling package, that is a chassis system and in your case I assume Freightliner. A Freightliner shop should be able to address your issue.

Perry White · 08-10-2012, 11:42 AM

Why do you think 210 is bad?

Steve Ownby · 08-10-2012, 12:44 PM

Quote:

Originally Posted by Perry White

Why do you think 210 is bad?

I didn't say it was bad. I said it should not be running 210 on level ground under normal conditions. I'm sure it's within normal temp range for that vintage when pulling a grade. The OP stated his temp would cycle from about 195 to 210 and then back over about a 5 minute time frame on level ground. That is not normal even if the range is ok.

spike45 · 08-10-2012, 09:42 PM

In my previous life as a Cummins (Fleetguard) field service engineer, I worked on a large transit bus fleet in LA area. Cummins Midrange Service provided me data that indicated the ISL family is designed to operate at up to 234*F. That does not mean it must run at those temps but that it is not detrimental to the design.

I see more complaints on thermal cycling events on motorhomes than I ever saw with the truck community. Why is that? The radiators are not installed such that the continuous air flow works to cool the coolant regardless of 'fan on' state. A temp of 210F is harmless. Depending on which thermostat the chassis manufacturer ordered on the engine, it could easily have been a 192*F setting. It cracks or begins to open at 192*F and is fully open at round 10*F above that. The thermostat's function is to control minimum engine operating temperature, not the maximum temp. Your foot controls the upper end of the temp range. Many LD gas engines cars with electric cooling fans operate such that the thermostat works as expected but the fan does not come on unless the engine load is such that if the thermostat is fully open and the temps continue to climb, the fan switch triggers at a higher but safe temp such as 210F. It is more noticeable since your radiator is either side or rear mounted lacking the benefit of the air flow over the core to do what the fan cannot do until it is switched on.

Spike45
Gary Spires
Retired Cummins (Fleetguard) Field Engineer

MDPD · 08-13-2012, 08:44 AM

Thanks all for your responses. It still bothers me to see the temps rising and falling (mostly rising) but I do feel better knowing the high of 210 will not be an issue down the road. I knew I could depend on your answers.