Results 1 to 25 of 25

Thread: Oil Leak on C85

  1. #1
    cubman's Avatar
    Join Date
    Apr 2002
    Location
    BNW (Boone IOWA)
    Posts
    44
    Post Thanks / Like

    Oil Leak on C85

    I am struggling to locate the source of an oil leak on my PA11. It is a C85-12f that was rebuilt last year. It appears the oil is coming from the rear (accessory case) area or perhaps the kidney tank. Push rod tubes, prop seal, etc. look dry. Has anyone ever used one of the UV oil leak detection kits to locate a leak?

  2. #2
    d.grimm's Avatar
    Join Date
    Oct 2004
    Location
    toledo, oh
    Posts
    470
    Post Thanks / Like
    I washed mine clean, ran it for a few minutes and dusted baby powder over the suspected areas.
    worked and cleaned off remaining powder with compressed air.
    Dave
    Likes Hardtailjohn liked this post

  3. #3

    Join Date
    Jul 2010
    Location
    Elizabeth, WV
    Posts
    491
    Post Thanks / Like
    Does your C85 have an O200 crank? And if so was the case drilled for a through bolt to strengthen it? If so the drilling may have nicked the oil vein in the case and you now have a leak from that through bolt on one side of the case under a cylinder. If that leak is too bad to live with you'll have to replace the case with an O200 case.
    You can't get there from here. You have to go over yonder and start from there.

  4. #4

    Join Date
    Sep 2003
    Posts
    6,535
    Post Thanks / Like
    Mine leaked a bit. At 50 hours I re-torqued all case and pan bolts, as well as cylinder nuts. Stopped it. Also watch that plate behind #2 - three nuts. It has pressure oil under it.

    Did not know we needed a through bolt. My STC was from 1996, although I assembled the engine in 2017.

  5. #5
    Cub Builder's Avatar
    Join Date
    Mar 2011
    Location
    North Central AR
    Posts
    640
    Post Thanks / Like
    Quote Originally Posted by cubman View Post
    I am struggling to locate the source of an oil leak on my PA11. It is a C85-12f that was rebuilt last year. It appears the oil is coming from the rear (accessory case) area or perhaps the kidney tank. Push rod tubes, prop seal, etc. look dry. Has anyone ever used one of the UV oil leak detection kits to locate a leak?
    As previously stated, wash it clean, dust with foot powder, run for a few minutes and check again. The the powder will absorb the oil at the leak to show where it's at. It's not unusual for the oil tank on the C-85 to crack just below the mounting flange. But could also be a gasket under a mag, seal or gasket on the tach drive, gasket on the starter mount, seal or gasket on the generator/alternator or even that gasket under the accessory cover. I've seen people change the generator and cut the gasket that is for the generator and the tach drive so they would only have to replace the generator half of the gasket. The back side of that gasket at the seam between the generator and tach drive covers the end of the counter shaft of the oil pump and will leak like crazy if one tries to split the gasket. Generally speaking, it's not hard to locate the leak, and once found, not hard to fix.

    It's also not unusual to find the tack drive seal or the generator seal to be installed backwards. The inner lip on those two seals should face towards the engine.

    -Cub builder
    Likes Hardtailjohn liked this post

  6. #6

    Join Date
    Aug 2017
    Location
    short final
    Posts
    36
    Post Thanks / Like
    IMG_2990.JPG
    I'd check gaskets if you have any superior airparts. This one is on a valve cover, but have seen several lately that had shrunk and split on different engines and components.All of them had been on recent overhauls. Chasing oil leaks sucks.
    Thanks Philly5G thanked for this post
    Likes Philly5G liked this post

  7. #7

    Join Date
    Jun 2018
    Location
    England
    Posts
    316
    Post Thanks / Like
    Quote Originally Posted by Another Cubber View Post
    IMG_2990.JPG
    I'd check gaskets if you have any superior airparts. This one is on a valve cover, but have seen several lately that had shrunk and split on different engines and components.All of them had been on recent overhauls. Chasing oil leaks sucks.
    I replaced my valve cover gaskets with silicone ones last year, the port side perfect and no leaks, the starboard side still spatters oil over the side cowl........ hmmmmmmmmm


    Sent from my iPhone using SuperCub.Org mobile app

  8. #8

    Join Date
    Aug 2017
    Location
    short final
    Posts
    36
    Post Thanks / Like
    The ones i have had trouble with are the red paper type. Have found the trick with the silicone, or any rubber for that matter, to be clean dry surfaces. As in cleaned with mek or acetone. Then precisely torque them and not over them
    Thanks flynlow, Philly5G thanked for this post
    Likes BC12D-4-85, Philly5G, Hardtailjohn liked this post

  9. #9
    wireweinie's Avatar
    Join Date
    Aug 2013
    Location
    Palmer, AK
    Posts
    2,283
    Post Thanks / Like
    Clean and dry with the silicone ones. If you use cork or paper gaskets, they need to be glued to the valve cover with 3M 1300 before installation. It's a trick I learned years ago, working with valve covers on cars.

    Web
    Life's tough . . . wear a cup.
    Thanks flynlow, Philly5G thanked for this post
    Likes BC12D-4-85, Philly5G, Southern Aero liked this post

  10. #10

    Join Date
    Sep 2003
    Posts
    6,535
    Post Thanks / Like
    I have some 1/8" thick cork from 1966 that seals perfectly. My latest engine got the red silicones, and they don't leak either. You need a cheapie expander tool to seal the pushrod housings.

    Do the torque recheck first.
    Thanks Philly5G thanked for this post
    Likes Philly5G liked this post

  11. #11
    cubman's Avatar
    Join Date
    Apr 2002
    Location
    BNW (Boone IOWA)
    Posts
    44
    Post Thanks / Like
    Thanks to all for your suggestions. This is one of the reasons SC.org is so great!

    Here's the latest. Everything forward is dry (prop seal, cylinders, case, etc.) Kidney tank ok too. Source of the leak appears around/near the alternator. I replaced a heavy generator when we rebuilt the engine. Just cleaned FWF again and will run it for a few minutes to try and isolate the exact source. Unfortunately, won't be able to get to work on it for a few day. I'll post the what is found.

    Cubman

  12. #12
    cubdriver2's Avatar
    Join Date
    Apr 2003
    Location
    upstate NY
    Posts
    9,649
    Post Thanks / Like
    An old white T-shirt works also. Rip it into 1/2" strips and tie them around suspected areas. The baby powder works but makes a mess and sometimes picks up oil blown around.

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
    Thanks Philly5G thanked for this post
    Likes Philly5G liked this post

  13. #13

    Join Date
    May 2017
    Posts
    361
    Post Thanks / Like
    When you build up an engine, check torque on every fastener, then re-check the next day! Itís amazing how much the torque will relax overnight after setting the torque the previous day.


    Sent from my iPhone using Tapatalk
    Thanks Philly5G thanked for this post
    Likes Philly5G, bob turner liked this post

  14. #14

    Join Date
    Jun 2018
    Location
    England
    Posts
    316
    Post Thanks / Like
    Quote Originally Posted by cubdriver2 View Post
    An old white T-shirt works also. Rip it into 1/2" strips and tie them around suspected areas. The baby powder works but makes a mess and sometimes picks up oil blown around.

    Glenn
    Sounds like a great idea and Iím going to try it as sounds a lot less messy than the talc! But is there a risk of fire? or is this suggested for shortish ground runs?


    Sent from my iPhone using SuperCub.Org mobile app

  15. #15
    cubdriver2's Avatar
    Join Date
    Apr 2003
    Location
    upstate NY
    Posts
    9,649
    Post Thanks / Like
    Wrap it around things and tie it, then go fly

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  16. #16

    Join Date
    Jun 2018
    Location
    England
    Posts
    316
    Post Thanks / Like
    Quote Originally Posted by dgapilot View Post
    When you build up an engine, check torque on every fastener, then re-check the next day! Itís amazing how much the torque will relax overnight after setting the torque the previous day.


    Sent from my iPhone using Tapatalk
    I came back today via the bicycle shop and bought a 25 inch/lb torque wrench


    Sent from my iPhone using SuperCub.Org mobile app

  17. #17

    Join Date
    Sep 2003
    Posts
    6,535
    Post Thanks / Like
    I think the smallest fasteners need 100 in-lbs. I will check. The cylinders need 35 and 42 foot lbs. a good Snap-On torque wrench is called for there.

    Do the oil kidney by feel - by the time you finish all the case nuts, you will have the "feel" necessary.
    Thanks Philly5G thanked for this post
    Likes Philly5G liked this post

  18. #18

    Join Date
    Jun 2018
    Location
    England
    Posts
    316
    Post Thanks / Like
    Checked and retorqued all the valve cover bolts to 20 pound inches, test flew for 3 short flights and greatly reduced spatter


    Sent from my iPhone using SuperCub.Org

  19. #19

    Join Date
    Sep 2003
    Posts
    6,535
    Post Thanks / Like
    Seriously - after an engine rebuild, a retorque is recommended by most good rebuilders after a few hours at operating temperature. Rocker boxes,while prone to leaks, are way down on the list.

    Please don't hammer me with the difference between rebuilt and overhauled. I should have used "assembled".
    Thanks Philly5G thanked for this post
    Likes Philly5G, Hardtailjohn liked this post

  20. #20
    BC12D-4-85's Avatar
    Join Date
    Feb 2016
    Location
    Fairbanks, AK.
    Posts
    1,436
    Post Thanks / Like
    As noted oil free surfaces for silicone gaskets are important (they'll leak). Once they leak cleaning is necessary before retightening. Eventually cork or fiber compresses and metal valve covers can deform and bell out at the fastener holes so check that surface that for flatness.

    Gary
    Thanks Philly5G thanked for this post
    Likes Philly5G, Hardtailjohn liked this post

  21. #21

    Join Date
    Jun 2018
    Location
    England
    Posts
    316
    Post Thanks / Like
    Quote Originally Posted by BC12D-4-85 View Post
    As noted oil free surfaces for silicone gaskets are important (they'll leak). Once they leak cleaning is necessary before retightening. Eventually cork or fiber compresses and metal valve covers can deform and bell out at the fastener holes so check that surface that for flatness.

    Gary
    Yes, my plan was to try a retorque with my new torque wrench (which worked beautifully!! - Bike Hut 2-20 NM) and test and if still spattering remove the covers and silicone gaskets and clean and refit, but just tightening to the recommended 20 foot inches has made enough of a difference, so no need to remove and refit, but will continue to monitor and r&r if the spatter increases again


    Sent from my iPhone using SuperCub.Org mobile app

  22. #22

    Join Date
    Nov 2007
    Location
    NW Mn
    Posts
    38
    Post Thanks / Like
    I had success finding an oil leak on my c85-12 using the uv leak detector and black light. I had cleaned, ran, cleaned flew, cleaned, retorqued all with no luck. When I used the leak detector I found a small crack at the weld where the oil sump is welded to the mounting flange. I got the detection fluid at the local Chevy dealership and they were kind enough to let me borrow their black light. Good luck
    Likes C130jake liked this post

  23. #23
    cubman's Avatar
    Join Date
    Apr 2002
    Location
    BNW (Boone IOWA)
    Posts
    44
    Post Thanks / Like
    Here's the latest on my oil leak. Took the alternator off and replaced it with a plate. Flew it for 15 minutes yesterday. Unfortunately, removing the alternator didn’t resolve the oil leak. Now looks like it might might be coming from up around the tach cable or below the left magneto.


  24. #24

    Join Date
    Jan 2003
    Location
    nd
    Posts
    3,116
    Post Thanks / Like
    theres a washer under the tach cable adapter, people use a brass crush washer there and thats not whats suppose to be there, it uses a solid brass washer, a continental part number. and remember if you mess with that tach adapter the threads are backwards. or maybe just a mag gasket?

  25. #25
    cubman's Avatar
    Join Date
    Apr 2002
    Location
    BNW (Boone IOWA)
    Posts
    44
    Post Thanks / Like
    I determined the leak was coming from around the alternator, tach or maybe right mag by using the UV leak detector. Replaced the alternator with a plate - still leaked. Replaced the gasket and added washers to the tach housing (maybe the nut ran out of travel before getting tight against the gasket). Flew for an hour this morning - no leaks.
    Thanks wireweinie thanked for this post

Similar Threads

  1. C-85 oil leak
    By JimC in forum Super Cub Sick Bay
    Replies: 1
    Last Post: 05-02-2007, 12:45 PM
  2. oil leak help
    By Taledrger in forum Super Cub Sick Bay
    Replies: 6
    Last Post: 08-24-2005, 08:57 PM

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •