I got a deal on a 456 Coal Ramp/3456 Hopper Car at my LHS. However, someone tried to free up the plunger on the hopper car with WD-40 or some other solvent. This slightly softened the plastic on the hopper doors, adding to the stickiness. I disassembled the door/plunger assembly and wiped the doors and the door openings on the car body with a dry paper towel, then I drenched the plunger assembly in WD-40 to dissolve the 60 year old gunk. Once free, I wiped the plunger assembly dry. Now the car works fine. NEVER USE ANY KIND OF SOLVENT ON PLASTIC. I got LUCKY on this, you may not!!! Take the time to take it apart to clean it!!!