Coolant temp on FL XC chassis

[garysu]

I purchased a new 2006 dp in July, 2009. It has a cummins 400 ISL eng. with side radiator.I had a coolant temp alarm go off going up the moutain on I40 between Old Fort and Black Mountain NC headed west. It was at the top and the alarm went off within probably 10-15 sec. I thought the transmission would downshift as needed.My temp runs 200 deg on flat with or w/0 toad. Is this to high? Does anyone else run this temp between 62 and 65 mph? Do I need to manually down shift into 5th or 4th gear when approaching a grade? I read on another (Cummins) site you should keep the rpm up.

My BIL has a 2007 Monaca with the 400 ISL cummins with rear radiator and his temp runs a good 20 deg. lower than mine. I've read where this is a FL design problem ( not a large enought fin area on the radiator, needs to be larger) to you need to keep the rpm up. Would a lower temp thermastat help?

Anyone here have this experience and or solution without breaking the bank?
Thanks

Gary

 

[Utclmjmpr]

I have had this problem only once with my ISC, was climbing at 9900 Ft. and the trans stayed in 5th., pulling this hard a diesel will make a LOT of heat and since then I will drop to 4th. if pulling that hard. I also have the side radiator.>>>D

 

[BernieD]

Gary

I think your coolant is running about 20? hot. I have an ISL 400, side radiator on a Spartan 40' chassis. My normal running temperature is about 181?. On hot days running on level ground, it may climb to to about 190-195?. If I get into hills or mountains, it will get up to 201?, where the radiator fans kicks on, and it stays in that range. In heavy climbs (like up to the Continental Divide near Denver, it'll climb to about 210-215?. The hottest I've seen was a climb in Canada, 90? ambient temperature and 8% grade for about 18 milles, it got to 218?. I normally have the cruise control set around 62 mph. I leave it in cruise when I climb the mountains, tho I increase the cruise setting to about 65-67 mph. The high temperature warning doesn't come on till about 225-230?

When was the last time your radiator was flushed and coolant changed? Has the radiator and CAC been cleaned? Cummins like to run at lower RPMs than CATs, Cummins reps even suggest letting the engine lug at around 1350 rpm. If you want a little cooler setting, change the mode to standard and downshift manually to 5th gear, otherwise just let the cruise control do it's thing.

By the way, the rear radiator will run cooler since the radiator fan is on more than the side radiator.

 

[garysu]

Bernie,

The  unit is a 2006, but it's new in the sense that it had never been sold. It has about 3500 miles now but was around 2500 miles when it over heated. The coolant and radiator look as if it just rolled off the factory line.

From what I read this is a FL XC chassis problem. I think the radiator is undersized, but was curious if anyone else was having the problem.

Gary

 

[Biker56]

Cummins reps even suggest letting the engine lug at around 1350 rpm.

Hummmm! My Cummins doesn't even start having good torque until 1,600 RPM and going up long 6% hills.
It likes to be manual downshifted to keep RPM at least around 2,100 for keeping coolant around 198-200.  Doesn't even reach max HP until 2,400 RPM.

1350 is really lugging it with a ISB, and just asking for high temps. going up hill in the above 206 range.

Don't be afraid to use that Touch pad to keep RPM's up. That automatic part of the transmission doesn't have eyes to see how much climb is ahead.

On the other hand a ISL reaches its peak torque at 1,300 RPM.  ;D

 

[Utclmjmpr]

Bernie, which cassis do you have?? my Spartan uses a hydraulic motor driven fan (side) that runs when ever the engine runs, I have overhauled this motor and have tested it. It also shares the hydraulics with the power steering unit.>>>D

 

[Jeff]

Gary:

I run a Cat on a FL chassis with a side mounted fan that cycles between 195-201 degrees on warm days. I know those are normal range temps for the Cat and can't believe they aren't well within the range for your Cunmins. The range is determined by the Freightliner installed fan controller that cycles the fan on as needed.

We all are told repeatedly to downshift to higher RPM's for cooling on longer grades and that will probably resolve your higher temps.

Remember that side radiator fans take a LOT of HP to run so if your temps are set lower the fan will run more often, affecting your mileage. About this time of year when the temps drop below 70 degrees or so our fan stops running completely unless we are pulling a grade. My summer mileage is usually .5 mpg lower than winter mileage that I attribute to fan operation.

You can call Freightliner Tech support (1-800-385-4357) to verify all this but I am pretty confident you do not have a problem and there is no "design flaw", it is simply operating as designed.

 

[Jeff]

Bernie, which cassis do you have?? my Spartan uses a hydraulic motor driven fan (side) that runs when ever the engine runs, I have overhauled this motor and have tested it. It also shares the hydraulics with the power steering unit.>>>D

utahclaimjumper.:

When I first got our Tradewinds we were getting less than 8 mpg running just under 60 MPH. Our first trip to the Quartzsite Rally was almost our last when we arrived blowing dust all over the place. ;D ;D When everyone saw us coming they assumed I was driving25 MPH but in fact it was the fan that was creating the dust cloud. Because of that I called Freightliner who told me to start the engine cold and run the engine up to at least 1000 RPMs and check for fan operation. IF the fan was running the controller was bad and they fail to the ON position to protect the engine from over heating. At the time our coolant temps stayed at 182 degrees, the thermostat setting, unless we were climbing a long grade or it was very hot.

Upon investigation it was determined the controller was bad and as soon as it was replaced the temps started cylcling between 195-201 on warm days. Our fuel mileage is now around 9 mpg overall average and easily reaches 9.5 to 10 on cool days.

PS: As I read this and Bernie's numbers it would make sense that the Spartan Chassis is running cooler IF the fan is in fact running continuously because most of these rigs have 180-185 degree thermostats. As I said that was exactly what we got until the controller was replaced anf the fan started cycling.

 

[Utclmjmpr]

Jeff, thanks for the heads up, when I drive the coach we average about 9-10 MPG, when the wife drives we get closer too 12, go figure.>>>D

 

[Jeff]

Jeff, thanks for the heads up, when I drive the coach we average about 9-10 MPG, when the wife drives we get closer too 12, go figure.>>>D

And she doesn't beat everyone off the stop sign, right? ;D ;D ;D

 

[garysu]

Jeff

Thanks, I feel much better now.That totally makes sense.

Gary

 

[BernieD]

Utah

I have a 2001/2 Spartan MMGT chassis. I have a 2 speed (on/off) fan. Later years, Spartan went to a continuously variable speed fan. My fan also is driven by hydraulics.

Jeff

My fan thermostat is set at 201?. Doesn't kick in till then. The coach runs between 181? and 190? most of the time with no radiator fan running.

Gary

Our first coach was a Damon UltraSport on an FL chassis with a CAT engine/rear radiator and fan. The whole first year we had it, it overheated just looking at a 6% climb. Turned out, one of the issues was the design of the air flow thru the engine compartment. Damon had to add more venting in the rear cap to increase the flow. That's when I learned to use cruise control.

CAT engines seem to like to run at higher RPMs when climbing, maybe because it has less torque than Cummins. I manually downshifted the tranny much more aggressively with the CAT to keep the RPMs up and to limit shifting by the tranny. The Cummins with more torque and a maximum torque reached under 1400 RPMs works differently and I just letthe tranny and cruise control do their things. Cummins advises to let the engine lug, that's the way it was designed. Now I am talking about ISL/ISC engines, can't speak for ISB engines.