I have R3531 (30129), a lovely model, smooth running and reliable, and which I run with the Hornby pull-push set. However it has a strange issue; from cold, and run bunker first, it has a whining/grinding noise which doesn't affect the running quality, and which gradually fades to silence after being run for 5-10 minutes. Occasionally this also happens when running chimney first, but less frequently. I hesitate to be taking the thing apart to see what might be going on (I have no idea what to look for anyway!), so can anyone suggest what it might be? I thought it might be poor gear meshing, but as it seems to disappear with running I'm a bit baffled...
Thanks.