Arnold, I agree with you 100% about the possibility of damage to tethers from frequent connect/disconnect. I always pick my steamers carefully as a loco/tender unit and have not experienced any problems. Just don't twist the two units as you move them (and don't let your grandson do it!).
Regarding the quantity of smoke fluid, it sounds like you're not using enough. I use 10-15 drops as a minimum after the smoke output diminishes to a wisp. I arrived at this formula after lots of trial and error, but I won't be surprised of some Forum members disagree.
Bryant, if smoke is blowing out of the engine - even from the bottom and sides - the fan is probably working. The most likely culprit is a bubble in the stack. I always blow down the stack after I fill it. Some engines are more prone to bubbles than others.
John
