Overheating when in idle

General things to check for, presuming there's no leaks:

Is engine fan turning on when at high end of operating temp? (make sure no belt slippage also)
Any clogging or airflow obstructions to radiator face/fins?
Allow engine to cool enough to take radiator cap off, start engine and wait for temp to increase & thermostat to open (to circulate coolant).
Do you see any air bubbles in the coolant (in radiator)? If so, possible head gasket/o-rings problem.

 

If it overheats @ idle, check for fan coming on @ correct temperature, clogged fins on radiator. For some reason the air is not flowing through radiator fast enough.

 

You need to replace the radiator, flush the entire system then bleed the system once you replace the coolant.

No matter what, the problem isn't with anything but a really clogged radiator.

 

i could see a clogged radiator if he was driving down the road. but not sitting at an idle.

 

What he said! The radiator may have leaked and when it was patched up it blocked out several passages ways thus not giving the radiator enough area to flow at an idle to cool the coolant. I hope this helps.

 

Check and make sure your belt tensioners are still strong. You may be getting enough air movement and rpms at highway speeds, but not enough at idle, and the ISX pump is driven off of the belt.

 

don't forget that the '05 is most likely a CM870 or early 871 with an Air operated turbo actuator. If its got excess boost because its stuck or the control box is going bad, at idle, it can contribute to overheating it too.

 

I understand the confusion but it really doesn't work that way,

See even at idle the engine produces a lot of heat, the thermostat keeps the temps regulated but if it is open, it means that the engine has to circulate the coolant to cool, having a plugged radiator it can't get rid of the heat and because the water pump isn't what they call a positive displacement pump, it sits there just spinning. The low speed of the water pump isn't supposed to produce enough pressure to push the coolant through with it blocked so the engine overheats, if it did, then it would bust a radiator or hose.

I had this exact problem - overheats at low or no speed and it was the radiator.

When I took the radiator off, I cut it open to see if it was bad and 80% of it was blocked in the bottom 6 inches of it. This truck had 528k on it and overheating was a problem for a long time.

By the way, even in 80 degree weather, the fan should stay off unless you have the A/C on, which the fan produces enough air flow to lower the condenser temps down.

 

I have D12 engine and at idle,when EGRs cycle, it gains temperature to the point when fan has to kick in to cool down the engine,

my mech said its totally normal for EGR engines.. unless you have no or blocked EGRs!!