Does it do this when running with the other locos? That could be diue to the speed not being right. If it does it while running alone as well it could be something putting a bind on the drive or it could be a short in the motors windings. I've had that happen before.
Dr. Frankendiesel aka Scott Running BearSpace Mouse for president!15 year veteran fire fighterCollector of Apple //e'sRunning Bear EnterprisesHistory Channel Club life member.beatus homo qui invenit sapientiam
If you can do a load test on all three engines, you are certain to find the one drawing 30-60% more amperage than the other two. It would then be a matter of determining the cause. Sticky motor, tight, misaligned, binding, dirty drives...maybe a combination? Hardened oils mixed with dog hairs and house dust can't be a boon to axle rotations.
I dissassembled and cleaned the end drive of my Walthers indexed 90' turntable a few months back. It had maybe 20 minutes of accumulated use ("rotating-the-bridge" minutes). I was dismayed, and quite surprised, to find hairs and ground foam bits and other 'stuff'' mixed in and around the tiny white plastic gears. Maybe your slightly used diesel has 3-5 hours of use.
-Crandell
A motor heating up is usually an indication of a binding in the mechanism. However, if you're running the loco in question in tandem with others, you may have a speed mismatch, where the other loco(s) are putting a drag on the one overheating. If you're having this problem when running it by itself, you may need to disassemble the mechanism and hunt down the place where the mechanism is binding.
I have three identical Atlas/Kato C-424s in BC Rail colours. All are lightly used preowned that I converted to DCC. Two run beautifully together and were easy to speed match. The third smells hot when warmed up and then slows down. Yet it seems very lightly used and I can't believe the brushes or anything could have worn out. It is lubed up, but not overly done.
What are the usual areas to look for when a loco runs hot and slow?