Cummins ISC overheats at idle **most of the time**

Here is a video of the coolant flow for an ISC 8.3. Note in the early part of the video where they talk about a vent line and vent tube. See post #7 from BoxCarKidd.
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Didn’t come up with much of anything additional searching QS.

There are revisions to the water pump. I’m still pulling the pump and putting in the latest part. Inspect the water inlet for foreign objects.

 

I know it is a bit of a stretch but the only thing I could thank of. If an air vent was not working properly possibly it creates an air pocket at idle. Then when at road speed coolant flow is fast enough to to flush the air out.

 

Thanks for all the help guys

And boxcar. That might be the first thing I check because Ive always thought that the issue might have to do with an air bubble being created by something to restrict flow.

But all this is great advice so thank you all. The video references a top mount radiator reserve tank but this truck uses one on the fire wall. However I'm sure it's still basically the same in terms of cooling and vent lines. I'm going to tear into this in January and I'll see what I can find, so thanks again