M7 mystery noise help please.

[AndyG]

My R3531 is a beautifully smooth runner-and here comes the 'but'. From a cold start it runs almost silently, but after a few minutes a gear-grinding/whining noise develops and gradually grows in volume, eventually becoming unbearable. This happens when running in either direction, but appears to be quite random; sometimes I can get through a running session with no issues, and sometimes the noise develops when running forward but not in reverse, and vice versa. I should add that the running quality is not affected, and I pair the loco with the pull-push set. Can I also add that I'm hesitant to start fiddling around inside with all the separately added parts needing to be removed and replaced. As of now the M7 makes an attractive ornament in my cabinet, and deserves better... Thanks for any suggestions.

Edited October 9, 2018 by AndyG

[34theletterbetweenB&D]

That set of symptoms suggests heat build up in a bearing. Most probably the motor bearings as that is where the rotational speed is greatest.

 

Willing to take the body off? If so run the model until the noise has got going, then check if either of the motor bearings are hot. If a bearing is hot, apply a tiny dot of light oil and see if that kills the noise very quickly after restarting the motor. If so, then you have cracked it.

 

If not, then further thoughts will be required.

 

As a next step see if you can locate whereabouts on the model the racket is emanating from. (If it is inside the motor, then motor replacement is the likely course.)

[hallmodelspares]

I would also check any motor mounts to see if there is any play which may move the worm enough to cause a slight rub of the motor worm on the casing when running. as its able to move well I would rule out the gear being the cause