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Old 05-26-2010, 08:53 AM   #1
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Fleetwood Owners Club
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Water Temp rising to 3/4 during hill climb: Is this normal?

I have driven up a few hills and noticed the water temp is sensitive to the hill. Normally, the water temp gage stays right in the middle, but as soon as I hit a grade of maybe 4%, the water temp will start going up and up. I'll back off the pedal, downshift several gears until it levels off. As soon as I get to the crest of the hill, the temp will immediately go back to normal.

No alrams, no indicators, nothing.. Just the water temp gage issue
I checked the radiator air-flow,,, no problems
Coolant mix,,, 50/50 and full
2008 Fleetwood Providence 40E (42 feet)
Mileage: 3,500
Cummins 8.3 ISC 360hp 1050 ft lbs 268 kw (Power band: 1,800 to 2,200 RPMs)
Allison MH3000
Gross Combined Weight Rating (GCWR) 41,000 lbs
My current Combined Weight is (MH and Toad): 32,000 lbs

I called Cummins, Fleetwood, and two Freightliner places. They say this is normal.. I think the water temp gage would have gone into the red if I had not backed off and off and off and downshifted 3 gears from 6th to 3rd.

I ended up climbing the hill at about 25 MPH. We are going on our first long trip soon through Colorado with concerns about some serious mountain climbing. Turbo maybe? Water Flow? Just reaching the motor's max?

I must admit, Fleetwood should have put the 8.9 ISL 425 hp in this motorhome. The 8.3 ISC seems to be at its capability. I have read the Cummins 8.3 ISC is one of the best medium duty engines around with people easily getting 600,000 to 800,000 miles out of them. It is a typical workhorse motor for various commercial vehicle applications.

Is there a chart that shows what size motor fits the load?

Sorry to babble.. How can the same 8.3 ISC motor have hp ratings vary from 250 hp to 360 hp with large torque varriances? That's a lot of difference for the same size motor block.

I have a Ford 2006 F-350 6.0L diesel and it never heats up climbing very steep grades.

Fleetwood Providence 2008 40e
Ford F-350 4x4 Diesel 6.0L 2006
Honda CR-V 2006
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Old 05-26-2010, 09:13 AM   #2
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That would certainly not be normal for my CAT C7 350hp. My temp changes very little when hill climbing. Have you cleaned your radiator lately? Maybe dirt is reducing air flow.

Joe & Loretta Fischer
2017 Roadtrek Zion SRT
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Old 05-26-2010, 09:16 AM   #3
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first, the dash gauge is imo to optimistic, mine does the exact same thing.
when it did it on our maiden trip i about freaked
if you have the info bar that scrolls through the 2.5 million data points, you can select the coolant/water temp, and then watch it for real temps
my temps will climb to 212-212 then the fan kicks in and they quickly drop to 180-185 and will hold that for sometime.
then slowly climb back to 210-212 and the cycle starts all over
last summer 65-67 mph tooling across north new mexico, climbing 4% grades
it never went ant higher than the flat land temps.
this was in 5th and 6th, with the occasional drop to 4th, and 55mpg ish
i asked cummins about the 212 and they assured me it was well within range and the dash gauge is reading ok at 3/4 hot like yours
we are at 38k-40k loaded out with toadie
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Old 05-26-2010, 09:28 AM   #4
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What do you mean when you say you have checked radiator air flow and it is fine? If you have a rear radiator I suspect you need a good exterior radiator cleaning. Your ISC is working hard on those hard pulls and the radiator is not able to deal with the heat. When you down shift you are keeping your rpm's high in your power curve and the fan speed high while decreasing the demand on your engine.

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Old 05-26-2010, 09:40 AM   #5
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This unit is a rear-radiator. I took a garden hose to the radiator.. Nada... It was clean. I can see right through the radiator from the inside. While standing behind the MH, the air-flow coming out is a tornado. The fan blade is stiff and is always on while the motor is running. I'm not sure if the fan is a variable clutch or not. It always sounds like it is at max.

While on this subject, I'm hearing side hydraulic driven radiators take 25-75 horsepower. The main reason for side-radiators are due to the motor cooling demands and there is not sufficient room in the rear to accomodate a HUGE radiator.
Fleetwood Providence 2008 40e
Ford F-350 4x4 Diesel 6.0L 2006
Honda CR-V 2006
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Old 05-26-2010, 12:37 PM   #6
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Putting a garden hose to the radiator will not clean a rear radiator system. Oil comes back from the motor and the slobber tube and coats the radiator and dirt mixes with the oil and water will not touch it. Go buy 2-3 cans of spray engine degreaser like Gunk. Spray the entire radiator area from the front and the back to make sure it gets in between the fins. Let it soak for about ten minutes then blast it with high pressure water from a hose with a nozzle on it. Now you know it is clean. My temp would go up climbing hills until I did this. It still goes up a little which is normal and I just downshift to keep it cool.
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Old 05-26-2010, 12:51 PM   #7
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It is normal. When our coach was about two weeks old and we were headed up I-77 it was doing exactly the same thing. This is a Cummins 425hp in a Freightliner chassis with rear radiator.
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Old 05-26-2010, 12:56 PM   #8
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With only 3500 miles on the coach I'd be surprised if the radiator has had time to get dirty. My maiden voyage up the I5 Grapevine to L.A. turned into a debacle that ended in being towed back to Bakersfield to a Cummins dealer. Bottom line was that I was only a little low on coolant and it triggered the "Stop Engine" light.

The Cummins tech told me to be sure and "drive the tach" when climbing hills in hot weather. He said to keep the rpm up to 2000 and adjust the gear and speed to accomplish that.

Since then I pull up the actual eng temp on my information center to keep a close eye on it during hot weather climbs and I follow the techs advice and have had no problem. Pulled the Colorado hills over the 11,100 ' summit at about 50 mph, 218 degrees, with the Explorer towed behind. I have the 400 ISL.
Rick, Nancy, Peanut & Lola our Westie Dogs & Bailey the Sheltie.

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Old 05-26-2010, 04:59 PM   #9
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Hi Batman_777,
I have the ISC 330 HP engine and am a little over 37K total lbs. My ISC does the same a yours (since new). Spartan has cleaned out the radiator, I've tried the previously posted method to clean the radiator, I've also used compressed air to clean out the radiator. At this point, I do not think it is the radiator. I run the RPM solution mentioned in an earlier post. It helps.

I was out West last year. The only real problem I had was the Eastbound pull out of Laughlin, NV on route 163/68. Like you I was down to 25 mph with the temp near the top of the gage. FYI, the outside temp was well over 100 degrees F. It was late July. By watching the temp gage and keeping the gearing so the temp did not get high enough to derate the engine we were as slow as any truck climbing the hill. All other pulls (RMNP, etc,) were no problem.
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Old 05-28-2010, 07:07 PM   #10
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The secret to keeping your temps down while going up steep grades is to keep your rpm's up in a DP.

Use your Allison Control Pad to downshift and get your rpm's up prior to climbing the grade. You will not start to bog down and your temperature will not rise appreciably if you try this technique. If you normally cruise in sixth at say 1750, downshift to get your revs up to around 2200- 2400 and maintain that engine speed up the grade.

The Allison will not let you over-rev going up or down. Keeping your coach in a lower gear going down the grade will keep you off the brakes, control your speed and also will not cause your engine to over-rev.

I have the mechanical C8.3 forerunner of the ISC. By doing the above I climbed Fancy Gap and the temp in August only rose from the normal 190 to slightly over 200, never slowered below 55 MPH.

1998 American Eagle 40EVS
Cummins C8.3 325 HP
Allison 3062 Six Speed Transmission
Spartan Mountain Master Chassis
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Old 05-28-2010, 09:38 PM   #11
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cat c7 all the way baby I never seen over 201 and that was up hill towing a big 24 foot enclosed car trailer loaded with bikes and tires and tool boxes,etc, very heavy trailer, good luck finding a solution to your problem. Joe
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Old 05-29-2010, 04:49 PM   #12
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Our Diplomat does the same thing. Hey if your motor is working harder it only stands to reason it's going to run hotter.I hose my rad out on a regular basis and as of today it runs cool.
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Old 05-30-2010, 05:28 PM   #13
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You might think you have the air flow but you don't. It is not normal for the temperature rise you are talking about. The CAC is dirty and can only be washed from the front side. Spray simple green or similar cleaner on it. Let sit and wash good from inside with normal water pressure and nozzle. You will see a difference.
Jerry & Carol
Max, the Snauzer
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Old 03-18-2011, 03:53 PM   #14
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I have a 2008 Excursion 40E 8.3 W/360HP (2007 EPA engine), 11,500 miles and temp guage is at 3/4 (209) driving 62-64 on flat I-75 in FL. It drops to 201-203 if I drop back to 55. Techs they this is normal "within range", but what will happen at 6% grade and 95+ temp?

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