I have a 1984 spotscoach III with 454, aux tank is on right side between door an batteries main tank is in rear. Both tanks when above half tank at time while running and other times with nothing running, gas comes out the hole where you put gas in? it has done it in cool weather and hot? So i joke it makes gas any help would be great?

That's a strange one indeed.  Must be something pressurizing the tanks somehow.  Better have someone check it.

How is the coach sitting when this happens, level or at an angle? If its level then I'm with Cooperhawk something is causing pressure to build in one of the tanks forcing the fuel to the other. I would also check where the two tanks connect if its at the bottom the coach wouldn't have to be at much of an angle for the fuel to run in the other tank.

you could find some one in your town that has a inner engine inspection camera.Such as for checking the internal part of the heads after a race to see if the engine is legal. Then maybe they could look in side of your tanks for you.
The device would probably be in the hands of the "TECH' guy at the local roundy round race track. IT is a common item for Race track owners or thier "tech" guys.
WiDELOAD 55 .

I"M NEW and LOOKING FOR ANY AND ALL INFOP about a PROPANE POWERED unit on a 1979 Winnebago.
I'm looking to buy this unit. and would just like as much info as i can muster up.

I would check the gas caps. One could be a vented model and the other a non- vented. That would maybe under some conditions to blow gas out the tank vent lines. One that I had was someone had switched the two small lines, one for the return from the fuel pump and the other one for the generator. It was all i could do to put fuel into the tank! I would check that as well. I once i had figured out what had happened I had found a older styled canister fuel vent and hooked it into the carburetor. Mines old enough that it had that style on trucks but was missing from mine. It just vented right into....air...Someone before me had most likely taken it out and disposed it but the holes for the vacuum senders were there and an old book for Chevy helped. Getting vented caps should do it but I would also look to see where the fuel lines and exhaust system runs.

I am late with a reply but I happened to be researching fuel problems today and found the attached information that describes problem you encountered so I thought I pass it on.
Mickey