FlyingMonkey Posted October 26, 2014 Report Posted October 26, 2014 I cleaned out my drip trays (they had a light film of gummy residue) the other day, then flew almost every day this week. I then re-checked the trays, and there was a light fuel film there: The question is, what is normal for these trays?
Tom Baker Posted October 26, 2014 Report Posted October 26, 2014 Andy, my opinion is they should stay cleaner than that. I see signs of the leak on the carb itself, but it could be coming from the rubber flange.
CT4ME Posted October 26, 2014 Report Posted October 26, 2014 That's what was happening on my old bird, until carb cleanup and new gaskets. I'd say "normal" is clean, but not unusual to see some grime. That's why there is a tray there.
FlyingMonkey Posted October 26, 2014 Author Report Posted October 26, 2014 Sigh...Lockwood just replaced all the carb rubber and gaskets in June.
Tom Baker Posted October 26, 2014 Report Posted October 26, 2014 Andy, I see fuel stain on the carb higher than the bowl gasket. It shows above the Idle mixture screw, but looks dry higher up. Where the little BB is looks like the sealer is chipped away and discolored. Could be you need to reseal that.
procharger Posted October 26, 2014 Report Posted October 26, 2014 If your carbs are out of sync vibration can cause them to puke a little.
Tom Baker Posted October 26, 2014 Report Posted October 26, 2014 Also make sure the clamp on the carb socket is tight.
FlyingMonkey Posted October 26, 2014 Author Report Posted October 26, 2014 BTW, it is the same on both sides: Is this considered dangerous or an airworthiness issue, or just a minor issue?
FlyingMonkey Posted October 26, 2014 Author Report Posted October 26, 2014 Andy, I see fuel stain on the carb higher than the bowl gasket. It shows above the Idle mixture screw, but looks dry higher up. Where the little BB is looks like the sealer is chipped away and discolored. Could be you need to reseal that. What type of sealant is used there?
FlyingMonkey Posted October 26, 2014 Author Report Posted October 26, 2014 If your carbs are out of sync vibration can cause them to puke a little. They were balanced in June at annual, and the engine has been running smoothly to my reckoning.
Tom Baker Posted October 27, 2014 Report Posted October 27, 2014 What type of sealant is used there? Roger says epoxy, but I'm not sure what variety.
FlyingMonkey Posted October 27, 2014 Author Report Posted October 27, 2014 Since Lockwood touched the carbs last, I sent them a note with the pics I posted. Maybe they will have an idea what's happening. I will look everything over next time I'm out there and see if I can figure it out. I might have to run the engine with the cowl off to get fuel flowing through and see if I can see where it's seeping. It's time for an oil change, so I need run the engine to warm the oil before changing it anyway.
FlyingMonkey Posted October 27, 2014 Author Report Posted October 27, 2014 Thanks Roger. The cork gaskets? Should I get a set of floats too and have my guy check them at the same time?
Anticept Posted October 27, 2014 Report Posted October 27, 2014 What, they put in cork!? If you can, get the phenolic gaskets next time you replace them. Cork sucks. I had 200 hrs on a new set of carbs and the cork was already degrading rapidly on both.
FlyingMonkey Posted October 27, 2014 Author Report Posted October 27, 2014 What, they put in cork!? If you can, get the phenolic gaskets next time you replace them. Cork sucks. I had 200 hrs on a new set of carbs and the cork was already degrading rapidly on both. Oh, I don't know, I just know some Rotax bowl gaskets are cork. Not sure what they are supposed to be for the 912ULS. I'm guessing these are the right ones, but it does't say what they are made of: http://www.cps-parts.com/catalog/rtxpages/15-00905.php?clickkey=41852
Anticept Posted October 27, 2014 Report Posted October 27, 2014 I have no idea. I got gaskets from leading edge air foils and they are phenolic (edit: maybe fiber per roger?). The only time I had seen cork was with the new engine, and they suck.
FlyingMonkey Posted October 27, 2014 Author Report Posted October 27, 2014 I have no idea. I goet gaskets from leading edge air foils and they are phenolic. The only time I had seen cork was with the new engine, and they suck. I was just going to order some from CPS or Lockwood (I think CPS is cheaper by a buck). They are factory Rotax gaskets, so I guess they are whatever they are supposed to be...fiber, phenolic, viton, unobtainium...whatever.
FlyingMonkey Posted October 27, 2014 Author Report Posted October 27, 2014 Thanks Roger...ordered from CPS so they should be fiber.
Runtoeat Posted October 27, 2014 Report Posted October 27, 2014 Andy, I had wet drip trays and had fuel stains running down my engine mount from where fuel leaking from my carbs flooded my trays enough to run thru a hole in the side of the tray where a nylon zip tie to connects that helps hold the tray in place. I had new float gaskets installed and this seemed to eliminate my fuel weep. As usual, Roger's advice is sound. One thing I notice though is the small ball which is epoxied in looks kind of funky in your picture. Hard to tell by you picture and it might also be the clamp on the rubber carb socket needs tightening, but if you still experience wet drip trays after installing new bowl gaskets, you might check out these two items.
FlyingMonkey Posted October 27, 2014 Author Report Posted October 27, 2014 Andy, I had wet drip trays and had fuel stains running down my engine mount from where fuel leaking from my carbs flooded my trays enough to run thru a hole in the side of the tray where a nylon zip tie to connects that helps hold the tray in place. I had new float gaskets installed and this seemed to eliminate my fuel weep. As usual, Roger's advice is sound. One thing I notice though is the small ball which is epoxied in looks kind of funky in your picture. Hard to tell by you picture and it might also be the clamp on the rubber carb socket needs tightening, but if you still experience wet drip trays after installing new bowl gaskets, you might check out these two items. Thanks Dick...my slight leak is obviously nowhere near as severe as yours was. I will get my mechanic to replace the gaskets, and we will check all of the connections and the epoxied ball when we are in there. The question that has not yet been answered: How much fuel in the trays becomes a safety of flight issue? Mine seems to just be a little film with no ppoling at all, but is any fuel in the tray a grounding condition? The weather is so perfect right now here, I hate to not fly while waiting for gaskets to arrive!
FlyingMonkey Posted October 31, 2014 Author Report Posted October 31, 2014 Hmm...I checked yesterday and could not see any stains or other indication on the carbs of where the fuel in the tray had come from. I cleaned the trays out with Simple Green, and then went flying and checked again after landing, No fuel in the trays following that flight (6 touch and goes, about 0.8hr total). The day I did noticed the fuel in the trays, I had done some particularly aggressive maneuvering, including some ~2g turns and unloading to 0.2-0.5g for a couple of seconds at a time once or twice. Is it possible my carbs are fine in normal flight, but higher than normal positive g or less than 1g (but not negative) could cause a tiny amount of fuel to seep out?
Ed Cesnalis Posted October 31, 2014 Report Posted October 31, 2014 Do you usually remember to close your fuel valve but sometimes leave it open while in the hangar between flights?
WmInce Posted October 31, 2014 Report Posted October 31, 2014 Do you usually remember to close your fuel valve but sometimes leave it open while in the hangar between flights? If left open, that puts static pressure on all fittings, due to head pressure from full tanks. When the fuel is flowing, it does not seem to cause any problem, but sitting statically, I have seen fuel seeping from the gascolator. That valve should always be off when the airplane is sitting. The exception being, when a fuel sample is taken during preflight inspection. Following such a sampling, if the airplane is not subsequently flown, valve should be returned to off.
Tom Baker Posted October 31, 2014 Report Posted October 31, 2014 If left open, that puts static pressure on all fittings, due to head pressure from full tanks. When the fuel is flowing, it does not seem to cause any problem, but sitting statically, I have seen fuel seeping from the gascolator. That valve should always be off when the airplane is sitting. The exception being, when a fuel sample is taken during preflight inspection. Following such a sampling, if the airplane is not subsequently flown, valve should be returned to off. In my opinion as a mechanic, and you can take it for what it is worth. If you have fuel seeping from the gascolator at any time you should have it looked at, because that is not normal. There are many other high wing aircraft that leave the fuel on all of the time, and they don't have leaking gascolators.
sandpiper Posted October 31, 2014 Report Posted October 31, 2014 I keep my fuel valve closed when parked, especially inside. Sometimes I forget and have never seen any leakage when this happens. My main reason for keeping it closed when parked is to prevent spillage caused by a carb malfunction. I remember reading something on this forum, or maybe the old one, where someone had this problem. I also keep blocks under my axles when in my hangar. This is in case of a flat with fuller tanks which could cause fuel to leak from the low wing vent. Once in place, I rarely have to adjust them. They stay put and I always park in the exact same spot. I haven't tested to see if fuel would actually leak with a flat. Any volunteers?
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