George, or others, do you have suggestions for the best place (spelled cheapest) to purchase the vented gas caps? For some time now I have been using some automotive caps (chrome--look good & don't rust) and they are vented. The only thing is gaskets of the type we all recognize that fit "legal" caps don't fit the type above. I have a slight leak on the right tank, don't know if it is the cap or just what. Also get water in the gas if left in rain or washed. Have tightened screws w/ no success. Thinking about possibly going with Monarch Caps--guess that would eliminate water in fuel, need for new vented caps, etc.
Will appreciate comments.
Ole Pokey
Gas Caps & Gaskets
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
Frank, The filler neck is threaded (not unlike a pipe) into the fuel tank adapter. The adapter is held with screws to the tank. All this is sealed with sealant. (Usually Pro seal or PRC, but I've also seen Permatex used successfully.) If you've moved those screws you may have damaged the formerly water-tight seal and need to re-do the whole thing.
The Monarch caps (ugly in my opinion, but effective) might be your best solution, but don't do that thinking it will solve all your water problems until you address the sealant that's been disturbed. The problem MAY be resolved if you also purchase Monarchs kit that fills that "moat" with a cover.
Otherwise, if you wanted to stay "original" (that's just a joke, folks. Frank has a 172 converted to a taildragger) you'd have to purchase genuine Cessna caps. http://www.cessnaparts.com/
The Monarch caps (ugly in my opinion, but effective) might be your best solution, but don't do that thinking it will solve all your water problems until you address the sealant that's been disturbed. The problem MAY be resolved if you also purchase Monarchs kit that fills that "moat" with a cover.
Otherwise, if you wanted to stay "original" (that's just a joke, folks. Frank has a 172 converted to a taildragger) you'd have to purchase genuine Cessna caps. http://www.cessnaparts.com/
I agree that the original caps look better, but since the AD regarding a vented cap came along you can forget about looking original in that respect. I NEVER had any fuel flow issues until my mechanic caught the fuel cap thing. Since I wound up with only one original cap and one vented one I had constant fuel flow issues due to one vented cap. So I figured, if I HAVE to have a vented cap (which is not original and looks stupid in combination with a real original one) I might as well have two vented caps and solve my fuel flow problems. Viva Monarch! 
BTW, The "moat" cover from Monarch does a fine job at preventing water from getting into the tank as it is sealed with some sort of sealant or epoxy (I forget exactly what). If you do it, just be sure that you don't forsee any need to get into the fuel tank bays anytime soon. Once you glue those bad boys down you can forget about getting them off in one piece. I asked the guy at Monarch about removing them if necessary and he said he'd never seen one survive removal without some damage. On the up-side though, he said that he'd send me a replacement at no charge if I needed to do it. Nice guys.
BTW, The "moat" cover from Monarch does a fine job at preventing water from getting into the tank as it is sealed with some sort of sealant or epoxy (I forget exactly what). If you do it, just be sure that you don't forsee any need to get into the fuel tank bays anytime soon. Once you glue those bad boys down you can forget about getting them off in one piece. I asked the guy at Monarch about removing them if necessary and he said he'd never seen one survive removal without some damage. On the up-side though, he said that he'd send me a replacement at no charge if I needed to do it. Nice guys.
Doug
Fuel Caps
Thanks guys for the input. George, I am trying to keep my "172 TD" ORGINAL, whatever that is!
George, didn't someone post a thread some time back with a different way to put on Monarch moat covers so that the neck or whatever could be removed w/o destroying the sealed down moat cover?
I had the water problem before I attempted to tighten the screws & had no success in turning them. Plane was painted & screws painted over. Still think it must be a cap leak.
Ole Pokey
George, didn't someone post a thread some time back with a different way to put on Monarch moat covers so that the neck or whatever could be removed w/o destroying the sealed down moat cover?
I had the water problem before I attempted to tighten the screws & had no success in turning them. Plane was painted & screws painted over. Still think it must be a cap leak.
Ole Pokey