gt5-33
Tamarac, Florida
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Joined: 06/08/2004
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I have a 1996 newmar Mountain Aire with the 460 Ford V8 Engine. Just recently I have had the following problem. The water temp will rise up to the upper end of the normal operating range at speeds of 40+. In the city and/or stop lights the water temp remains in the middle of the normal range. Why does the engine get hotter at highway speeds. Did not do this in the past. Thanks for sharing, Tom
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John&Joey
Northern MN
(Baby it's cold outside)
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Joined: 05/20/2007
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Is the fan running during city driving and not highway?
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topflite51
In The Desert of Nevada
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Joined: 05/13/2004
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Thermostat only partially open
Plugged radiator externally not allowing enough airflow
Plugged radiator internally not allowing enough waterflow
 David
Just rolling along enjoying life
w/F53 Southwind towing 87 Samurai looking to golf or fish
Simply Despicable 
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Diplomat Don
Moorpark, Ca
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gt5-33.....There are going to be several things to check, usually starting with the cooling system as mentioned above. You also need to check the catalytic converter. They routinely got plugged on models a few years older than yours. They will cause the symptoms you're having. If it is plugged, you should also see some loss in power.
Don & Mary 
2005 Monaco Diplomat 36SKT
400 Cummins
2007 Dodge Dakota 4WD
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geezer34nh
New Hampshire
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It is really simple. Gasoline when burned produces about 125,000 BTU’s per gallon. When you increase speed you are burning more gallons per hour developing more heat. As the radiator ages it develops a crud in the tubes restricting the flow of coolant. This stuff cannot be flushed out. So as you increase speed the system cannot get rid of the heat fast enough and up goes the temperature.
Brad & Lucy aka the Geezer & The Hedgehog
1990 Foretravel 38' DP
Kitty Kat: Earl
Whitey Ford the Explorer riding the car trailer
Navigation: CoPilot 9 on a lap top
ASE Master Technician
SAE
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Gale Hawkins
Murray, KY
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geezer34nh wrote:It is really simple. Gasoline when burned produces about 125,000 BTU’s per gallon. When you increase speed you are burning more gallons per hour developing more heat. As the radiator ages it develops a crud in the tubes restricting the flow of coolant. This stuff cannot be flushed out. So as you increase speed the system cannot get rid of the heat fast enough and up goes the temperature.
Brad is point on.
It seems in the MH enviroment at about 10-15 years of age the effectiveness of radiators can take a nose dive due to several factors. They can look fine and NOT leak but are failing internally as Brad states and externally (fins breaking loose at the tube connect but it can not be seen until the radiator is pulled apart.
Recoring or replacement the radiator can be a good way to save buying a new transmission.
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96Bounder30E
Orange County, CA
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Thermostat.......Thermostat.......Thermostat.......Thermostat.......Thermostat.......
Thermostat.......Thermostat.......Thermostat.......Thermostat.......Thermostat.......
Thermostat.......Thermostat.......Thermostat.......Thermostat.......Thermostat.......
Thermostat.......Thermostat.......Thermostat.......Thermostat.......Thermostat.......
Thermostat.......Thermostat.......Thermostat.......Thermostat.......Thermostat.......
If you doubt what I am saying........look at what I'm driving.....I've been there done that......got the $500 T-shirt to prove it!
Search my posts from late 2003 and see the posts I made about that exact same problem........I thought there was no way it could be a $6 thermostat so I spent $500 replacing everything else......in the end a $6.00 thermostat was all it was
Eric
96 Bounder 30E-F53(460)
stock Ford intake w/K&N air filter
used Thorley headers
new Banks resonator, muffler, tail pipe and 4" polished SS exhaust tip
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John&Joey
Northern MN
(Baby it's cold outside)
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96Bounder30E wrote:Thermostat.......Thermostat.......Thermostat.......Thermostat.......Thermostat.......
Thermostat.......Thermostat.......Thermostat.......Thermostat.......Thermostat.......
Thermostat.......Thermostat.......Thermostat.......Thermostat.......Thermostat.......
Thermostat.......Thermostat.......Thermostat.......Thermostat.......Thermostat.......
Thermostat.......Thermostat.......Thermostat.......Thermostat.......Thermostat.......
If you doubt what I am saying........look at what I'm driving.....I've been there done that......got the $500 T-shirt to prove it!
Search my posts from late 2003 and see the posts I made about that exact same problem........I thought there was no way it could be a $6 thermostat so I spent $500 replacing everything else......in the end a $6.00 thermostat was all it was
Like you, I go with the simple easy fixes first. About 90% of the time it's the problem.
I only talked about the fan because it comes on when things get very hot and then it drops the temp in a heart beat. Might not be coming on at highway speeds but during city driving.
Like bounder, check my rig also.
"I sure enjoy the four seasons; Spring, Summer, Fall, and South of I10."
- 1996 Cruise Master (Pre Coachmen)
- 33.5 foot wide body (no slides)
- 460(7.5L EFI) V8,E4OD, F53
- 2002 Saturn SC2, Roadmaster Falcon 2 tow bar, Brake Buddy
Past RV Campsites.
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Dutch_12078
Great Sacandaga Lake, NY
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Joined: 10/07/2008
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The thermostat, or the lower hose sucking in and restricting the flow, are both low cost repairs that could resolve the problem. A couple of squeezes on the lower hose to see how soft it is can rule that one in or out fairly quickly. My '95, and I'd expect your '96 as well, does not have a catalytic converter, so that shouldn't be an issue.
Dutch
'95 Coachmen Catalina 322XL
F-53 chassis, 460 V8
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RLS7201
Some Where
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The 2 main cooling problems of that year 460 were thermostats and fan clutches. If it cools in city driving, then the fan clutch is probably OK. No catalytic converter that year 460. Very little history of radiator problem on 460s. If your radiator cap is holding 15 psi on the cooling system, then hose collapse is not an issue. As suggested by 96bounder30e, change the thermostat.
Richard
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