alun Posted August 12, 2009 Report Share Posted August 12, 2009 i had the most water ever yesterday when draining the left tank. the whole fuel tester was full with about a cm of fuel on the top. took about 7-8 goes at draining before it was clear. its not like we had a whole lot of rain either. any idea where this could be coming from? the fuel tanks caps were on propertly (as in flat), the plane is just back from annual and the rings were done in Feb before that. I just wonder if there is a way that something could be draining into the wing from somewhere else? thanks guys Quote Link to comment Share on other sites More sharing options...
N57039 Posted August 12, 2009 Report Share Posted August 12, 2009 Good description by Jim. FYI (on my M20J anyway) the big 0-rings are MS29513-338 and the little ones are MS29513-010. All four of these together represent all of $4.00 worth of parts, so there is no excuse for not changing them at least annually. It's an easy job to do (under your A&P's supervision, of course). When it's apart to change the little o-ring, spray everything liberally with Tri-Flow, and you'll get a very smooth operating closure. BTW, I use a Scotch Brite pad to clean up the contact surface of the large o-ring on the wing opening. Quote Link to comment Share on other sites More sharing options...
Piloto Posted August 12, 2009 Report Share Posted August 12, 2009 A good way to check leaks on the caps area is: Have someone blow air by mouth into the tank vent. Spray a bubble detergent like SD-20 around the cap perimeter and check for bubbles. If after replacing the caps O rings you still have bubbles you may have a leak in between the cap adapter ring and the skin. This leak occurs when the adapter ring is rusted thru. You can either replace the ring or apply sealant from the inside. Also remove the drain valve to insure the tank is water free, José Quote Link to comment Share on other sites More sharing options...
wmrunyon Posted August 13, 2009 Report Share Posted August 13, 2009 Gentlemen, Great input on protecting the fuel cap seal. Triflow is great stuff and worked quite well lubricating the moving parts of the cap making its function smooth and easy. When my plane came out of annual this past spring (at a MSC), i noted on preflight that the O-rings had not been replaced. So i brought it up and they scurried about and replaced them acting a bit perturbed. In past annuals at a different MSC it had been part of the annual, which i brought up. They responded it was not part of the Mooney Inspection List. Needless to say, they were cracked and i had just expected them to be replaced. About a week later i got another invoice for the O-rings, two of them. I was so stinking mad, as i assumed they replaced all four. I should have watched them! Dangit. So i flew back recently to make the point, and made them do the inner rings. From what i understand, its the inner rings that are more prone to be the source of a leak than the outer rings. What i found amazing, they did not know there was an inner ring on the fuel cap. I had a long chat with the head A&P explaining the level of anticipated service and attention to detail we expect in our planes. I continually wander what else they missed? Quote Link to comment Share on other sites More sharing options...
alun Posted August 13, 2009 Author Report Share Posted August 13, 2009 i heard back from my maintainance guy today. they have only replaced the outer rings so hopefully that will cure it. thanks for all the help guys! Quote Link to comment Share on other sites More sharing options...
fantom Posted August 13, 2009 Report Share Posted August 13, 2009 Note that the inner ring is more difficult than the bigger, outer ring to replace, so some shops just ignore them. Quote Link to comment Share on other sites More sharing options...
carusoam Posted August 14, 2009 Report Share Posted August 14, 2009 Check the collar that the cap seats in. They have a tendency to rust through without much notice. See my post on the other thread for fuel caps for additional detail. Quote Link to comment Share on other sites More sharing options...
Magnum Posted August 15, 2009 Report Share Posted August 15, 2009 I had a water problem, too. My Mooney is always hangared and I rarely fly in rain. My mechanic washed her and after that I had a lot of water in one tank, the problem was that the cap was not tight enough. Easy to fix, but I was shocked how long it takes to get all the water out. For the next 5-6 flights I found water in this tank although I always drained several times. I was glad to have two tanks, so I used the other one for T/O and landing. Since then I tape the caps before washing... :-) Quote Link to comment Share on other sites More sharing options...
carusoam Posted August 15, 2009 Report Share Posted August 15, 2009 Cap tightness is adjustable also... Not only are there two O-rings, but the bottom assembly can be rotated to make the overall tightness increase or decrease by the height of one thread for each rotation. (from experience) When all is well, there should be no water in the tanks, even if you park outside...Condensation is measured in drips, not in cup fulls... I noticed how serious the leaky collar ring was by observation while flying in the rain. I could see bubbles of air leaking out at the rings. The first hint was cupfuls of water. The second hint bubbles while flying in the rain. Time to get help, water in the fuel is pretty serious. draining water from the fuel takes 15 minutes - 1/2 hour of drain and replace, slosh the plane, drain and replace, slosh the plane. Sitting on your butt on the wet pavement, pushing on the nearest tire, listen for the slosh. Of course, don't slosh too hard, the water droplets break up and won't find the drain for an even longer time. An amazing amount of water can be hidden somewhere in the tank. Even after following this procedure, I have still found a few ccs water in the tank after the flight. Quote Link to comment Share on other sites More sharing options...
alun Posted August 28, 2009 Author Report Share Posted August 28, 2009 well the inner o rings were replaced and so far a big improvement. hopefully that's the cure. Quote Link to comment Share on other sites More sharing options...
hais Posted April 30, 2022 Report Share Posted April 30, 2022 If you have leaky caps, is it possible to accumulate enough water when flying in rain to cause engine failure? Quote Link to comment Share on other sites More sharing options...
carusoam Posted April 30, 2022 Report Share Posted April 30, 2022 13 minutes ago, hais said: If you have leaky caps, is it possible to accumulate enough water when flying in rain to cause engine failure? Most likely not, because…. On the top side of the wing is this large vacuum source… enough to lift the plane… What you will see…. Is air bubbles being pulled past the seal… a less than subtle hint that your fuel caps need adjustment… there are two O-rings, not just one… the water has difficulty getting past the flow of air… But, prior to flight… it is possible for water to be going past the same leaky seals… There is a ton of water that gets collected up hill and runs down past the fuel caps… so if water is leaking in… you can acquire a lot of water in a single rain storm…. So…. If you are getting water in the tanks…. Now is the time to check the seals and their adjustment…. Or the fuel neck that the cap seal is in contact with… PP thoughts only, not a mechanic… Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted April 30, 2022 Report Share Posted April 30, 2022 Wow…. We have discovered one of the earliest MS threads! Alun hasn’t been here in quite some time… haling out of the old England… Runyon and N57039 both sold their planes… Fantom has gone light sport (?), but still visits MS often… Magnum was last seen in Germany a few years ago… Piloto has resurfaced as Gagarin… and will be back again soon…. Say the strong rumors around here… I’m on a mission…. Best regards, -a- Quote Link to comment Share on other sites More sharing options...
hais Posted April 30, 2022 Report Share Posted April 30, 2022 58 minutes ago, carusoam said: Most likely not, because…. On the top side of the wing is this large vacuum source… enough to lift the plane… What you will see…. Is air bubbles being pulled past the seal… a less than subtle hint that your fuel caps need adjustment… there are two O-rings, not just one… the water has difficulty getting past the flow of air… But, prior to flight… it is possible for water to be going past the same leaky seals… There is a ton of water that gets collected up hill and runs down past the fuel caps… so if water is leaking in… you can acquire a lot of water in a single rain storm…. So…. If you are getting water in the tanks…. Now is the time to check the seals and their adjustment…. Or the fuel neck that the cap seal is in contact with… PP thoughts only, not a mechanic… Best regards, -a- Thanks. I sumped water from left tank. Since it was only left side and I flew through rain, I thought it must have been the fuel cap. I'll have the o-rings replaced. Quote Link to comment Share on other sites More sharing options...
hais Posted April 30, 2022 Report Share Posted April 30, 2022 51 minutes ago, carusoam said: Wow…. We have discovered one of the earliest MS threads! Alun hasn’t been here in quite some time… haling out of the old England… Runyon and N57039 both sold their planes… Fantom has gone light sport (?), but still visits MS often… Magnum was last seen in Germany a few years ago… Piloto has resurfaced as Gagarin… and will be back again soon…. Say the strong rumors around here… I’m on a mission…. Best regards, -a- Mission to bring them all back? 1 Quote Link to comment Share on other sites More sharing options...
Will.iam Posted April 30, 2022 Report Share Posted April 30, 2022 I had no leaks at my fuel caps before the annual but after the annual and filling up my wings on cheap $2.80 100LL at the time to tanker and test a fuel patch done under wing step as it seeped when full revealed in flight leaks around my fuel caps due to the blue stain streaks forming aft of the main caps. I was upset that working O-rings were removed and replaced as it’s easier to just go ahead and replace than just inspect but they had been done just last annual I can’t believe these o-rings fail that quickly, so i ordered some fluorosilicone high end o-rings that will last more than a few years and they are blue instead of black after installation no more in flight fuel streaks. 1 Quote Link to comment Share on other sites More sharing options...
Guest Posted April 30, 2022 Report Share Posted April 30, 2022 4 hours ago, hais said: Thanks. I sumped water from left tank. Since it was only left side and I flew through rain, I thought it must have been the fuel cap. I'll have the o-rings replaced. Mooney SB M20-229A is your guide. https://www.mooney.com/wp-content/uploads/2020/12/SBM20-229A.pdf Clarence Quote Link to comment Share on other sites More sharing options...
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