Cummins ISB 340 Engine Overheating Overheat Fan Clutch Thermostat Cooling etc.

[Britcanuck]

Originally Posted by Banning406

So glad to have found all this information about this problem. I agree whole heartedly that a class action suit should be upcoming. Our 2009 Berkshire 390BH with 340ISB CUMMINS has had the exact problem overheating on hills. We had work done at Cummins in Billings, Montana - radiator boiled out, thermostat replaced, turbo sensor replaced, EGR valve replaced, new antifreeze- $4300 later still heating up on the hills. Started researching and found this thread. Might have to try the direct drive fan.

Sorry to hear of your troubles but there are hundreds of us who have had the same experience. I had similar work done as you did and for a year it was OK.
Last year we were driving between Quartzite and Yuma after driving down from Canada no problem when up goes the temp gauge, on comes the alarm and the mild cussing begins. I pulled over and turned off, waited a few minutes and started up and all was good for 4 months and back to Canada. Go figure - I cant. I have a chum with a Cummins 350 in his Itasca and any incline causes the sympton. He has had EVERYTHING done and no resolution.
It has to be a software problem. Not as bad as B737 Max but same root cause

[ziaptrn]

Hello all - just to throw in my 0.02.
We own a 'new to us' 2008 Winnebago Journey with the 6.7L ISB EPA07 350hp engine and 55k miles on ISC rear-radiator chassis.

The previous owner had Freightliner replace the fan clutch due to all of the above symptoms before we purchased the rig.
We began experiencing the same tendency to overheat (although I never actually let it overheat - just watched the gauges perform EXACTLY as described). First I verified cleanliness of radiator and CAC and so on - all was well.
Cutting to the chase...I just returned from Camp Freightliner in Gaffney where their service department took a look. They suggested installing a "Guard Dog" instead of replacing the clutch, as the clutch itself is new (within 2 years) and there are no oil leaks, signs of slippage, etc.
The Guard Dog is a sort of override fan controller and is a small box that clips in to the harness that drives the fan.
Problem solved. Zero overheating and the fan cycles up and down as appropriate (like it should have in the first place). Cost for Guard Dog was $300.00. The Guard Dog is a product made by Horton
Horton Vehicle Products | Horton
I gave the techs at FL in Gaffney the SS Code 3737 and we discussed everything from just pull the fuse and leave the fan locked all the time, to replace the fan clutch, to a direct-drive solution.
Time will tell if I made the right decision, but at $300.00 it was a risk I was willing to take starting low and going slow versus yet another fan clutch still to have issues remain.
So far 3000k miles home and zero problems the entire return trip over 2 weeks.
Just to share my experiences. I'll post again if the 'fix' doesn't hold!!

[Banning406]

Originally Posted by ziaptrn

Hello all - just to throw in my 0.02.
We own a 'new to us' 2008 Winnebago Journey with the 6.7L ISB EPA07 350hp engine and 55k miles on ISC rear-radiator chassis.

The previous owner had Freightliner replace the fan clutch due to all of the above symptoms before we purchased the rig.
We began experiencing the same tendency to overheat (although I never actually let it overheat - just watched the gauges perform EXACTLY as described). First I verified cleanliness of radiator and CAC and so on - all was well.
Cutting to the chase...I just returned from Camp Freightliner in Gaffney where their service department took a look. They suggested installing a "Guard Dog" instead of replacing the clutch, as the clutch itself is new (within 2 years) and there are no oil leaks, signs of slippage, etc.
The Guard Dog is a sort of override fan controller and is a small box that clips in to the harness that drives the fan.
Problem solved. Zero overheating and the fan cycles up and down as appropriate (like it should have in the first place). Cost for Guard Dog was $300.00. The Guard Dog is a product made by Horton
Horton Vehicle Products | Horton
I gave the techs at FL in Gaffney the SS Code 3737 and we discussed everything from just pull the fuse and leave the fan locked all the time, to replace the fan clutch, to a direct-drive solution.
Time will tell if I made the right decision, but at $300.00 it was a risk I was willing to take starting low and going slow versus yet another fan clutch still to have issues remain.
So far 3000k miles home and zero problems the entire return trip over 2 weeks.
Just to share my experiences. I'll post again if the 'fix' doesn't hold!!

Thanks for the information! I had heard about the guard dog but want sure what it was.

[TDebrocke55]

I have a Bounder 5.9L ISB, 2001Freightliner chassis. When I contacted Source they have no info on Bounders. (really?). Anyway, they sell the fan but not the direct drive to eliminate it. How did you mount the fan to your Cummins? Where did you get the drive adapter?

[teptraveler1]

Originally Posted by TDebrocke55

I have a Bounder 5.9L ISB, 2001Freightliner chassis. When I contacted Source they have no info on Bounders. (really?). Anyway, they sell the fan but not the direct drive to eliminate it. How did you mount the fan to your Cummins? Where did you get the drive adapter?

If a direct drive fan is what you are wanting, locate the 5A fan clutch fuse and remove it. You will then have a direct drive fan. This is info obtained from a Freightliner rep at the Winnebago Grand National Rally. Thanks to ziaptrn I now know the location of the fuse on my motorhome. Next time I have an overheating issue the fuse will be gone. If Bounder is anything like Winnebago, it may not be in the most accessible location.

[Dwayne1]

I pulled my fan clutch fuse yesterday and took a 40 minute drive, heat gauge held right where it was supposed to.

[scooterbob]

Cummins ISB 6.7 2008 46K miles
Have been reading all post on this thread and I have all the symptoms of overheating, Have replaced thermostat and cleaned radiator .guess it is time for a clutch fan.

[scooterbob]

Is there some type of sensor or thermostat switch that turns the fan on and off ? When I run the engine it seems like there is a lot of air from the fan coming through the radiator but more on the top then the bottom. I would like to make the fan run all the time if possible.

[scooterbob]

Anyone have a copy of the Freightliner service bulletin SS Code 3737 they can post?

[scooterbob]

Located and removed the 5 amp fuse as shown on socket F-15 hopefully everything works out

[nathaniel]

Read all the replies and lots of great information so I am curious if the thread is still being looked at and if anyone has tried putting a toggle switch in the dash to by6the fuse to keep the fan on high when approaching steep grades to keep temp low and keep the fan from cycling from low to high? Was thinking this would help trans temp control as it takes so long to cool it back off once it gets in the 200 range? Am I over thinking this?

[scooterbob]

I am thinking the same thing a toggle switch

[scooterbob]

Removed the 5 amp fuse and today drove about a hundred and seventy-five miles. Temperature stayed right at 190-192 the whole time. Couldn't really tell if there was any change in fuel mileage because the wind was blowing a gale.

[scooterbob]

Today I rigged up a switch to the 5:00 amp fuse makes it a lot easier to turn on and off so I don't have to take the covers off on the side of the road.