Cummins ISL 8.9 400 HP

[nitrohog1]

Folks,  I just completed a 6000 mile trip around the Country in my 2011 Itasca Ellipse  42 ft, my engine is a Cummins ISL 8.9 400 HP and I pull a Honda CRV. I noticed that my engine Temp would top at 212 degrees then the Thermostat would open and the Temp would go down to around 185 degrees and cycle back and forth between the low and high temp My fuel mileage for the trip was 6.8 MPG and I Cruised at 65mph on the Interstate.I also did a lot of mountain driving. My questions for people with a similar coach and  length with the ISL 8.9 400HP. Does your Temp and fuel MPG work out about the same. I didn't know if maybe my Thermostat is not opening soon enough and causing the fan to kick in which would reduce my fuel mileage.

Thanks for you input,
Herbie

 

[SeilerBird]

Is it a rear radiator? If so your radiator might be clogged up a bit.

 

[nitrohog1]

Yes, the Radiator is in the rear. I have wash the cooling fins often and seems to make no difference.


Herbie

 

[Kevin Means]

Herbie, we have the same coach but we have the later 2011 build, which has the 450 horse engine with the DEF system. For what it's worth, we just got home from a 3200 mile trip - towing our Jeep. There was only one leg of the entire trip when the outside air temp was less than 90 degrees. Most of the time, it was in the high 90's and low 100's.

On three occasions, while climbing some of the many 6% grades we encounterred, the Silverleaf display indicated that our coolant temp hit 221 degrees. While that isn't the official "engine hot" temp of 241 degrees, I felt it was hot enough that I should manually gear down to increase RPMs and get the cooling fan to increase airflow. In each case, it pulled the temps down to 214 degrees within 30 seconds. That's not bad considering the outside air temp was 110 degrees when we started up one grade, and 112 degrees when we started up another. The hottest the transmission ever got was 205 degrees.

Like you, I set my cruise control to 65 mph. When driving on relatively flat roads, when the outside air temp is 60 to 80 degrees, our engine coolant temp runs about 198 - 204 degrees, depending on the steepness of any small hills we may be climbing or descending. Even when driving across the Arizona desert, when it was 115 degress, our coolant temp ran a pretty consistent 202 - 206 degrees. We averaged 7.1 mpg on this trip, which is pretty normal when we're towing. We average 7.3 mpg when we're not towing.

Kev

 

[Gary RV_Wizard]

That's pretty much the normal range for a Freightliner cooling system.  There is a water system thermostat plus a fan controller. The thermostat probably opened at about 160 F. so that water could flow through, but the engine computer controls the radiator fan. It reacts to the dash a/c (fan always runs at least at low speed when the a/c is on) and engine temperature.  Cummins says that 212 is ok operating temp for the ISL engine.
What you are probably seeing is the fan controller switching to max speed, which cools the radiator quickly.

 

[nitrohog1]

Guys, thanks for your help. It seems that Kevin and I are not far off as to engine Temps. I just wasn't sure if the Temps that I was reading were the norm or not. Gary, I appreciate your input, that makes me feel a lot better.


Herbie

 

[Gary RV_Wizard]

I should have mentioned that Freightliner provides a variable speed fan on their chassis with the ISL engine, so the fan speed ramps up as cooling demand increases. It's not a just a viscous clutch - the Engine computer monitors both engine and transmission cooling as well as the dash a/c demand and alters fan speed appropriately.  If the controller fails or monitoring capability is lost, the fan controller defaults to full on. It's noisy and sucks horsepower from the engine (and fuel from the tank), but it makes sure everything stays cool.

 

[A Traveler]

We have the same engine in our coach, on the Freightliner XCR side radiator chassis.

I would add to Gary?s comments by saying the Sauer Danfoss electronic fan controller on these engines is one AWFUL piece of equipment. I have had more trouble with it than anything else on the coach. I have had it up to my eyeballs with engine overheating caused by the failure of one or more components in this system. And while they say that the fail safe mode is to run the fan at full speed if the system fails, that is NOT true in all cases, mine being one of them. I actually demonstrated to Cummins via their InSite computer program that in one of the failure modes, the fan actually ran SLOWER as the engine got HOTTER!

Next week I am trashing this entire system and installing the Source Enginnering Wax Valve fan controller. I am done dealing with this crap. Simple is better.

 

[Gary RV_Wizard]

Traveler: What coach & chassis is this?  The fan & speed controller is not part of the Cummins-supplied engine, so Cummins has no say over the fan system except for overall cooling requirements.  The fan & the entire cooling system is chosen by the chassis builder.  The one in my 2003 Freightliner XCM chassis worked flawlessly for 10 years and then went to full-on operation.  I don't recall component manufacturer, so don't know if it was the same one you are having trouble with.

 

[Neal]

On our xc chassis, the fan is supposed to fail to full on if current is lost, but ours would randomly fail off, I think with current on. It was almost always on first start up, it would fail to start it in low speed mode. About a mile after take off, the hot engine warning would come on. We found if we stopped, then restarted it would work correctly. It gradually got worse, so we let freightliner take care of it.

 

[A Traveler]

Traveler: What coach & chassis is this? 

Gary, it is a 2006 Thor Mandalay 40E on the Freightliner XCR side radiator chassis. 400 HP Cummins ISL.

The coach is now back into the ?fan goes slower when engine gets hotter? fail mode. With ambient temps in the mid to high 80s it runs around 210 degrees on level ground at 65 mph. On a two mile, 2% grade (a tiny hill) it went to 216. Slow down to 40 mph or coast downhill and the temp will drop to 180.

I?m tired of screwing with it. Source Engineering Wax valve goes in on September 10.

 

[Gary RV_Wizard]

Thanks for the extra info.  As near as I can tell from the Danforth site, the Saur-Danforth control you have is a completely different animal than what I had in my XCM (modular) chassis with side radiator.  My fan was hydraulic-driven and the ECU had to command lower speeds; when desired, so the default was full-on.  I wasn't aware that Freightliner had that sort of variation in the cooling systems used with the ISL and a side radiator (the rear radiators are different).

 

[A Traveler]

The fan is also hydraulically driven in my coach. The Danfoss controller only commands two speeds in normal operation, low and high. And the ?advertised? fail safe mode is to run the fan on high. However, my experiences have shown that this controller evidently has more than one failure mode, and some of them lead to overheating.

Internally, the ECM reads engine temperature and commands a certain percentage of fan speed. Below nn% (not sure of this number) the fan is set to run on low speed and above nn% it will go to high. The notes in my maintenance log from the road test say:


?On a road test with InSite running on a laptop on board, the ?Fan Commanded Speed? parameter was going DOWN as the engine got hotter. At 190 degrees, the commanded speed was 40%. At 207 degrees it was 14%! Cummins confirmed this was not correct. We re-flashed the ECM, even though it was running the current and correct software version. This seems to have fixed the problem. On a road test after the re-flash, the Fan Commanded Speed never got below 48% and the engine temp never got above 203.?


It would appear that whatever went wrong before the re-flash has happened again. However, at this stage I no longer care. This entire system will soon be history as I go back to older, stable and proven technology in the Source Engineering Wax Valve controller.

 

[Gary RV_Wizard]

Good data, thanks again!  I'm pretty sure mine showed more than 2 speeds, but never had to investigate like you did.

Mine would command a moderate speed whenever the a/c compressor was engaged.  If no a/c, it would leave the fan off completely until about 170 F, then run it slow.  High came in around 203, as you observed.  I never paid much attention to the speeds in between, but I occasionally heard a change in fan speed if left idling for awhile on a hot day.  When driving, I could only track temperature and infer when the fan cycled up or down - my engine monitoring was rather limited compared to InSite or similar.

 

[A Traveler]

A very sharp Cummins Guy has finally found my overheating problem...I think.

I was going to install the Source Engineering Wax valve on the engine. The tech suggested that before we get deep into that install, he wanted to check a few settings in the ECM. He connected the shop laptop running InSite and started checking the fan settings in the ECM. There is a specific test that InSite runs that cycles the fan to different speeds by changing the percentage of ?Commanded Fan Speed.? With the type of fan control that I have on this coach, there should be only two speeds, low and high. The percentages set by the test should be 100% and zero %, so the fan runs on low and high speed. However, when he ran the test, InSite cycled the percentage between 100% and 50%! As soon as he saw that he said, ?That?s not right. That?s the test for a variable speed fan. This is a two speed fan system.?

He then checked another setting and discovered that my fan system was set to ?Variable Speed? in the ECM! THAT?S WRONG!

He changed the setting to the correct setup for my 2-speed controller and ran the test again. A moment later I heard a sound I have never heard before. It was the roaring sound of the fan running on high speed! How about that! I?ve owned this coach for 6 years and had never heard that before! The fan was plainly audible inside the coach, too.

On the way home, I purposely beat on the coach hard, to see what would happen. I hammered up one grade at 70 mph with my foot on the floor. The temp had been running around 205. It quickly climbed to 212 and then, with my foot still on the floor, beatin? on that big ol? Cummins as hard as I could, the temp started coming DOWN! It dropped back to 207 and stayed there, even with the throttle wide open. It had never done that before! Prior to this, if the temp got up to 212, the only way to get her to cool down was to back out of the throttle, slow down and shift down, to keep the RPM up around 2,000.

I think my overheating problem may be solved...finally.

 

[Mile High]

I've got the ISL 400 rear radiator.  Towing a Wrangler, it can run up to 220 briefly.  210 seems to be mid-line on the gauge.  I haven't ever tried to clean the radiator.  7.5 seems to be average mgp towing the Wrangler and I do have DEF.  I actually never remember how to reset the mileage, so it is either cumulative over months, or just the day.

 

[Gary RV_Wizard]

Good to hear it got resolved without modding the fan control.  Often such problems are simple to fix but very difficult to isolate.

 

[A Traveler]

Good to hear it got resolved without modding the fan control.  Often such problems are simple to fix but very difficult to isolate.

You can say that again, Gary! This is the 4th shop that looked at this problem and the only one to actually find the problem and get it right. I am hopeful that my overheat problem is now fixed.

By the way, kudos to Cummins Crosspoint in Fort Wayne, Indiana for this one.

 

[Mile High]

Good to hear!  Maybe I should get mine checked.

 

[timjet]

I doubt this will help but here goes: 2007 American Coach Tradition, Cummins ISL 400 hp, Spartan chassis, hydraulic fan, side radiator towing a Honda CR-V.  In the 20,000 miles I've driven it I've never seen 190 deg engine coolant temp on the silverleaf monitoring system. We drove Colorado, Utah, Wy, NM and everything in between, up the Eisenhower tunnel, west Texas with OAT of 106 deg. Never saw temp above 190, mostly hung around 180 - 185.

In flat Florida I rarely see the tranny temp above 140 deg. My rig needs a tranny temp of at least 140 deg to electronically check the tranny fluid level, which I can rarely do here in FL. However out west I did see tranny temps in the 160 range.

Engine coolant was changed 2 years (I think) before I bought it so I have not checked or changed the thermostat. Coach is pretty much at max GVW of 34,000 lbs.