Steve1300 Posted April 12, 2008 Share Posted April 12, 2008 We are currently working on some pump housing showing leaks. The plane has been in cold weather, so we also have some blade leaks, but nothing abnormal. The other herk forum has lost the old posts from back when this question was asked, so I am hoping that some of you ol\' prop guys will repost your answers. The pump housing actually looks simple when the covers are off, but they aren\'t simple when tracing the source of leaks when part of the propller assembly. I am interested the causes of \"lip seal leaks\" and those that just look like lip seal leaks. We have three props now that appear to be lip seal leaks and none of them were overserviced. Perhaps, when we get some of you to post some help for me here, I can save the whole thread so it doesn\'t get eaten up by the ether-net. Thanks in advance........:) Quote Link to comment Share on other sites More sharing options...
Lkuest Posted April 12, 2008 Share Posted April 12, 2008 I\'m sure the prop shaft seal leak has been mistaken for a rear lip seal leak many times. My rule of thumb is if the prop shaft leaks with aux pump pressure, it\'s the prop shaft seal. If it leaks as soon as you let off the aux pump, it may be a clogged breather preventing the venting of pressure out of the atmospheric sump or simply a worn rear lip seal. I\'m kind of ignorant though when it comes to clogged internal passages/filters/screens causing leaks. Quote Link to comment Share on other sites More sharing options...
Steve1300 Posted April 17, 2008 Author Share Posted April 17, 2008 Thanks for your input on that. We are having to deal with front cover leaks which I can only attribute to a pressurized atmospheric sump. We never find bad o-rings,but the fluid is getting past them. I am thinking that most \"lip seal leaks\" are not lip seal leaks at all. That\'s why there are other actions that have to be taken instead of changing the lip seals. Anyone else willing to get into the discussion? Quote Link to comment Share on other sites More sharing options...
Lkuest Posted April 17, 2008 Share Posted April 17, 2008 I\'ve had a Guard guy tell me he found an atmospheric dipstick mounting nut loose cause a leak from that area. Unfortunately, you have to take the front cover off to retorque it. Another thing to look out for is to make sure before installing a rear lip seal that the drain holes on the pump housing are at 6 o\'clock, otherwise there will only be one way for the vented fluid to go, and that\'s out of the rear lip seal. Quote Link to comment Share on other sites More sharing options...
duckhunter04 Posted May 1, 2008 Share Posted May 1, 2008 We had a period of time that one of the guys in my shop was putting the double lip seal on without putting the greese in between the lips. If the first lip seals works then the second one will heat up due to lack of lubrication and distort both lips. That cost us a few manhours but after he learned the correct way which is to read the book we have taken care of most of our can seal leaks! This is just one of the possible causes I have seen. Quote Link to comment Share on other sites More sharing options...
rysponycar Posted November 27, 2008 Share Posted November 27, 2008 I believe the cause of on an over pressurized atmospheric sump is the pitchloch regulator. I have had prop lip seal leak one after another so I took out the pitchlock regulator and disassembled it. Found the all the cups to be pretty blocked. Cleaned each individual one and put her back together. Installed and hasnt leaked from the lip again. I hope this helped? Quote Link to comment Share on other sites More sharing options...
FCCBohica Posted December 3, 2008 Share Posted December 3, 2008 I\'m sorry to tell you, but the pitch lock regulator has nothing to do with the atmospheric side of the pump housing Quote Link to comment Share on other sites More sharing options...
duffymp Posted December 8, 2008 Share Posted December 8, 2008 This has been a LONG time problem and there really is no exact fix to the problem. It may any one of many problems associated with that cover. The lip seal not being pressed in properly, dip stick seal or nut not torqued, cover plate seal, valve housing cover breather being clogged. A long time ago Hamilton Standard did a big study at Pope AFB in trying to determine exactly what the cause was. Out side of the normal stuff discussed earlier they found that almost 80 percent of prop leaks are caused by an over serviced propeller. During the study at Pope we found that some of the propellers had almost an extra gallon of fluid in them.... This is why it is so important to not just throw 2 quarts in everytime the low oil light comes on with out checking the servicing first. The book has the established way of checking servicing but you will find that a lot of the old heads do it differently. Remeber that a little fluid goes a long way. Quote Link to comment Share on other sites More sharing options...
pjvr99 Posted December 9, 2008 Share Posted December 9, 2008 An interesting \'aside\' to this story - in the cell, one of the things I watch during servicing, is the 115v 400Hz digital voltmeter. In a properly serviced and functioning prop, there is a drop of 0.6 volts when feathering or unfeathering. Yesterday I noted the voltage drop was still 1.1v. I believed that during servicing an air-lock had occurred, which is normally cleared by running the engine for 10 minutes. However after an hour of run time, I had some streaking down the inside/back of the blades and some mess on the lower afterbody. I decided to deservice/remove half a gallon of fluid. Lo and behold!! the voltage drop is suddenly 0.6v and the feather time dropped to 17 secs from 19. All this from a prop initially refusing to take more than 4.5 gallons of fluid ..... Quote Link to comment Share on other sites More sharing options...
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