Overheating At Idle

[SusanCamille]

I Have A 2008 NEWMAR 4304 Spartan Chassis 425 HP
It starts to Overheat in gear at idle, I cleaned the radiator, And Changed the two Hydraulic filters. It runs fine while on the road, The fan will go to high speed at 1000 RPMs..
Does Anyone know why this happens?
Any suggestions would be most helpful..

Thanks for Your Time;
Randy Burzynski
(SusanCamille)

[harleychief]

Randy, a diesel should cool at idle not heat. You said it happens when you're in gear, does it happen out of gear? Either way it is a control (electrical) problem, not mechanical. I would check the codes and see what popped if you can and then get it to Cummins.

[SusanCamille]

harleychief,
I'm not sure if it would cool down by taking it out of gear, Iv'e always raised the RPM's too 1000, the fan turns at a higher speed, then cools down. There is a 12 Volt wire going to the hydraulic fan motor pulling wire kicks fan to high at 1000 RPM's Unless already calling for fan, Do not believe it is electrical.