Hardened Oil Syndrome

If a person buys a NOS engine that has never been run from an auction site, what are the chances it will NOT run when power applied due to this H O S thing I have read about?  I asked the seller and they admitted it could happen and they would give back some money as reimbursement if I took the engine to a local hobby place.  I fix old turntables and stereos with stuck motors and sliders and controls using spray solvent tuner cleaner.  Would these Z motors respond to a couple shots of that?  In general, how serviceable are these Z engines?  I have fixed some N engines with TLC and delicate soldering and cleaning; are these the same only smaller?  Or does no one even try?  Thank you. 

HOS normally occurs in the gears of the loco not the motor. A shot of tuner cleaner will probably work well. Just let it soak in some. I've also used a few drops of Labelle #108 oil to loosen the old Marklin oil. You can also try putting it in a ultrasonic cleaner if you have one. I would suggest that you don't take the bottom plate off of a steam loco to clean it unless you enjoy fighting with small gears to get all of the wheels quartered correctly. Marklin engines don't need a lot of service. A tiny drop of oil on the gears, an occasional cleaning and, eventually, a change of motor brushes should be all you need to do.

Wow this is encouraging! But to replace brushes, don't the bottom wheels and gears have to come off? Or can you get to them from above or sides? Do you have ebay account for buying and selling Z stuff? And where do you get brushes? or just make your own? Do you want to talk outside here on email or whatsapp or something? I got my brand new track yesterday and it is sitting on top of my TV cabinet just waiting for a good deal on a running train.

You'll need to remove the shell (body) to replace the brushes. I only buy things on eBay. You can get the brushes on eBay but I prefer to get them from either Z Scale Monster or Z Scale Hobo. You can also buy new motors at either place. Z Scale Hobo is an authorized Marklin repair dealer (I think) so he usually has a better inventory. He also does repairs and general maintenance. Remember my advice to us a a Z Scale approved power supply/controller. I burned up several locos using an old N Scale power supply/controller.

You'll need to remove the shell (body) to replace the brushes. I only buy things on eBay. You can get the brushes on eBay but I prefer to get them from either Z Scale Monster or Z Scale Hobo. You can also buy new motors at either place. Z Scale Hobo is an authorized Marklin repair dealer (I think) so he usually has a better inventory. He also does repairs and general maintenance. Remember my advice to us a a Z Scale approved power supply/controller. I burned up several locos using an old N Scale power supply/controller.