BIGGDOGG
Alberta
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Joined: 07/14/2009
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This topic comes up fairly regularly, so I thought I'd share my experiences this past winter and spring driving from Alberta to Arizona with a 300 HP Cat DP.
While driving south last fall, all went well until we reached the high plains south of Salt Lake City, where the elevation is high and so is the speed limit. I put my foot down and kept pace with other traffic, actually passing some vehicles on the climbs up the long mountain pulls. Transmission stayed in 6th all the way up. As the ambient temperature rise, so did the engine temperature, and twice we had to pull over to let the motor cool down.
I took the motorhome to Freightliner in Chandler and asked them to clean the radiator fins and shroud, change the coolant and thermostats, and extend the slobber tube. This they did as well as regular maintenance service. They called and said there was a significant temperature differential between the top of the rad and the bottom and they recommended a rod and core as there appeared to be a restriction inside the rad. They cleaned the CAC and the rad while they were disassembled and buttoned everything up.
Driving back to Alberta last week was a different story altogether. Coupled with the service work and a complete change in my driving habits, we a stress- and trouble-free journey. I set the cruise control to sixty miles per hour and let the Allison transmission do the downshifting as necessary. I tried to keep the RPMs at about 1750, and as such experienced a MUCH better fuel economy as well. We got about 9 MPG going south, and 12 MPG coming north.
I have to thank many on this forum for sharing their experiences and insights, and I hope this little story will help some other new DP owner to be a little more confident in the mountains.
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Deetour
Washington
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Joined: 06/01/2011
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Its great you didn't cheap out and only do half the job. Well done sir!
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Gale Hawkins
Murray, KY
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Joined: 07/22/2007
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Good points.
10+ years seems to be about the max life of a new radiator before it starts to fail in one manner or another.
Some forget if the chassis radiator does triple duty (engine block and oil cooling plus transmission cooling that a failing radiator can shorten the life of both the engine and transmission.
The recoring of our 1992 P30 454 chassis lowered transmission temps by about 15F degrees. The PO had replaced the transmission 17K miles before we bought it so I am guessing it the old one had left some junk in that part of the radiator or the cooling fins were seperating from the cooling tubes.
Reworking an old radiator is never a waste of money if it is an OTR MH. Thanks for the message.
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wolfe10
Texas
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Joined: 10/08/2000
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Actually, radiator life is a LOT longer if coolant is changes as it should be, only distilled water and coolant used AND core kept clean.
"Core kept clean" on a DP means cleaning the FRONT of the CAC annually!
Brett Wolfe
1997 Safari Sahara 3540
EX: 1993 Foretravel 36' U-240
FMCA Forum: www.community.fmca.com/index
Diesel RV Club:http://www.dieselrvclub.org/
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Tom/Barb
Oak Harbor
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Joined: 10/16/2009
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What you did works, when you think about the load of air that you are pushing on the front of the coach you'll know why the fuel milage goes down above 60 miles per hour. I loose about 3 miles per gallon between 60 and 65.
2000 Newmar mountain aire 4081 DP, ISC/350 Allison 6 speed, Wrangler JK toad.
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RLS7201
Some Where
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Joined: 10/26/2002
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BIGGDOGG wrote: They called and said there was a significant temperature differential between the top of the rad and the bottom and they recommended a rod and core as there appeared to be a restriction inside the rad.
This seems like flawed logic. If the radiator is dissipating heat correctly, shouldn't the coolant temperature decline as it flows from top to bottom? Thus the radiator its self will be significantly cooler on the bottom.
Richard
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Gale Hawkins
Murray, KY
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RLS7201 wrote:BIGGDOGG wrote: They called and said there was a significant temperature differential between the top of the rad and the bottom and they recommended a rod and core as there appeared to be a restriction inside the rad.
This seems like flawed logic. If the radiator is dissipating heat correctly, shouldn't the coolant temperature decline as it flows from top to bottom? Thus the radiator its self will be significantly cooler on the bottom.
Richard
This has my attention since your post. 
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Klueck
Florida
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Joined: 11/15/2008
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wolfe10 wrote:Actually, radiator life is a LOT longer if coolant is changes as it should be, only distilled water and coolant used AND core kept clean.
"Core kept clean" on a DP means cleaning the FRONT of the CAC annually!
and how exactly is that done,(cleaning the front of the cac annually) if you don't mind.
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topflite51
In The Desert of Nevada
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Joined: 05/13/2004
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Gale Hawkins wrote:RLS7201 wrote:BIGGDOGG wrote: They called and said there was a significant temperature differential between the top of the rad and the bottom and they recommended a rod and core as there appeared to be a restriction inside the rad.
This seems like flawed logic. If the radiator is dissipating heat correctly, shouldn't the coolant temperature decline as it flows from top to bottom? Thus the radiator its self will be significantly cooler on the bottom.
Richard
This has my attention since your post. If the radiator is sinificantly hotter on the top of the core than on the bottom, that would be an indication of poor flow and the radiator would need to be 'rodded out' or recored.
 David
Just rolling along enjoying life
w/F53 Southwind towing a 87 Samurai or 01 Grand Vitara looking to golf or fish
Simply Despicable 
Any errors are a result of CRS.
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zmotorsports
Utah
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Joined: 11/29/2007
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RLS7201 wrote:BIGGDOGG wrote: They called and said there was a significant temperature differential between the top of the rad and the bottom and they recommended a rod and core as there appeared to be a restriction inside the rad.
This seems like flawed logic. If the radiator is dissipating heat correctly, shouldn't the coolant temperature decline as it flows from top to bottom? Thus the radiator its self will be significantly cooler on the bottom.
Richard
If the temperature differential (Delta T) is too much this is an indication that the flow through the radiator is insufficient to cool properly. Usually a temperature differential of around 15-25 degrees is an indication that you have good flow through the radiator and the radiator and coolant are expelling heat correctly.
When the flow is insufficient through the radiator it backs up the heat into the engine and an overheating condition occurs.
Mike.
2003 Monaco Dynasty/ 26' Haulmark Edge trailer
2011 Jeep Unlimited Rubicon
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