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Old 09-15-2010, 10:11 PM   #1
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overheating problem cummins 300

Have a 2000 fletwood discovery with the 300 cummins gets hot when going up hills then cools down on leavel ground.Started doing this after they fixxed dash air also runs hotter than it did before they fixxed the air.Dont know what it will do in mountains yet but going to soon any advise would help.Turn the air off and that dont help.


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Old 09-15-2010, 10:46 PM   #2
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The first thing to check would be the rad. Some 300 chasisis had a slobber tube that would allow the fan to spray oil into the charge air cooler (and the rad), the oil would cause any dust blown through to stick and eventually you've got a rad operating at reduced efficiency. You can search the issue and get lots of hits on what to do. I tried the simple green method sprayed in from the engine side with the motor running to distribute it around the rad. I'll know soon how well it worked but visually it looks a lot better than it did. Good luck.

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Old 09-15-2010, 10:53 PM   #3
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look on the caterpillar forum for 3126 overheating (notorious)
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Old 09-19-2010, 03:07 PM   #4
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Originally Posted by atomic98 View Post
look on the caterpillar forum for 3126 overheating (notorious)
He as a Cummings. Not a cat.
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Old 09-19-2010, 03:44 PM   #5
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Originally Posted by ninos View Post
He as a Cummings. Not a cat.
In the case of a 2000 Discovery the engine make, makes no difference. What matters is the radiator location, and this DP has a rear radiator! If the 300 Cummins has a breather tube and it's not extended it will contaminate the radiator just like a Cat. The solution is to bring the slobber/breather tube aft of the fan and fan shroud Once that is done the method of cleaning a rear radiator is the same whether the MH is Cat or Cummins powered.
2001.5 Fleetwood Discovery 37U 330HP Cat
Toad-2008 Yamaha Royal Star Tour Delux
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Old 09-20-2010, 02:53 PM   #6
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barring it being gummed up..an easy way to check the rad for clogging is to let the engine run up to temp so that the thermostat ( another thing you might want to check ) opens. shut the engine OFF and run your hand up and down the cooling grid. it should be warm or hot all the way up and down. if you encounter a cold spot that part of the rad is clogged. also ( i am not familiar with MHs) do you have a separate tranny cooler? if not a lot of tranny collers run through the rads and that makes them heat up more. lastly you might try a different rad fan. BUT if you say this happened only after "they" worked on the dash air...i would check the rad and then take it back to "them".
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Old 09-21-2010, 06:11 PM   #7
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Cleaned radiator and extended tube will let u know soon how that helped plan on going to maryland from missouri this sunday.Thanks for all the advise first trip in motorhome new to all this but ready for the experience.

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