Filler cap Tilley AL21 leaking air

Discussion in 'Fettling Forum' started by bp4willi, Feb 14, 2021.

  1. bp4willi

    bp4willi Germany Subscriber

    Offline
    Joined:
    Jan 21, 2014
    Messages:
    662
    Location:
    Niers, Germany
    Hi all,
    I need your advice for an AL21 filler cap.
    Its leaking air.
    Air leak is not from the pump.
    Air leak is from the thread.
    I used 3 different rubber rings for seal.
    Nothing helps. Neither force at tightening the filler cap on tank.
    Tank thread seal surface looks ok too.

    How is the joint of filler cap and pump. Is that screwed?
    What else might be wrong ? Or helpful ? IMG_20210214_141226.jpg IMG_20210214_141119.jpg IMG_20210214_141330.jpg
     
  2. David Shouksmith

    David Shouksmith United Kingdom Founder Member

    Offline
    Joined:
    Sep 6, 2010
    Messages:
    7,735
    Location:
    North-East England
    The thing with o-rings is that they're meant to have some means of being held in place and they don't always work well where there's a degree of freedom of movement possible - as in the case of a Tilley pump clamp washer. I can understand using them in a short-term / nothing else to hand situation and they might just get you out of a hole but not as a direct replacement for the correct washer or seal. I think that's where your problem arises. Probably what's happening is as you tighten down the pump, the torsional forces are distorting the o-rings, thus the leak of air and loss of pressure.

    I'd say cut yourself a correctly sized and shaped washer from a sheet of rubber - good quality nitrile will do the job but Viton is better. Failing that, contact Ross at The Fettlebox...
     
  3. george United States

    Offline
    Joined:
    Nov 8, 2011
    Messages:
    2,894
    Location:
    USA
    Plain and simple, O-rings were not designed for this purpose. Try and find a flat gasket @bp4willi.
     
  4. bp4willi

    bp4willi Germany Subscriber

    Offline
    Joined:
    Jan 21, 2014
    Messages:
    662
    Location:
    Niers, Germany
    I tried as well with a flat gasket, shown in last pic.

    How is Filler cap and pump tube connected? Screwed, soldered, pressed??
     
  5. podbros

    podbros United Kingdom Subscriber

    Offline
    Joined:
    Dec 27, 2015
    Messages:
    1,618
    Location:
    Wirral
    Hi @bp4willi ... The older ones definitely screw on, but yours may be a later model so not sure?

    Is the base date stamped at all?

    @JEFF JOHNSON

    Hey, just a thought, it's not 'bottoming-out' at all, is it ??? :-k
     
  6. David Shouksmith

    David Shouksmith United Kingdom Founder Member

    Offline
    Joined:
    Sep 6, 2010
    Messages:
    7,735
    Location:
    North-East England
    OK, I thought that was the old one that you'd removed - I was misled when you said "rings".

    Fresh Fettlebox seals are 3.1mm thick - what thickness material are you using? The 'bottoming-out' theory is a possibility if your pump cap is the screwed together type. It's a fine thread and sometimes they're a bit difficult to get apart. When you get it apart, there should be a seal-supporting ring in there, too.

    Sorry to be a bit sketchy - it's a while since I've needed to faff about with these seals and there are probably different versions of the pump assembly. Jeff will know better...
     
    Last edited: Feb 14, 2021
  7. JEFF JOHNSON

    JEFF JOHNSON United Kingdom Subscriber

    Offline
    Joined:
    Nov 28, 2010
    Messages:
    11,183
    Location:
    Shetland Islands UK..
    The pump which is shown in the photograph is a late 1960s/1970's replacement pump and the build quality of those pumps is not that good, so my advice is to try an older Tilley pump which you know is functional and in my opinion, the Fettlebox clamp washers etc., are of very good quality, there are others for sale on Ebay which are made of an inferior substance.

    This link shows several of those pumps.

    1960s or 70s replacement pumps
     
  8. Henry Plews

    Henry Plews Subscriber

    Offline
    Joined:
    Jun 23, 2014
    Messages:
    1,734
    Location:
    North Yorkshire
    @bp4willi If your pump is the same type as on my ex-Bundeswehr AL21, it's soldered.
     
  9. bp4willi

    bp4willi Germany Subscriber

    Offline
    Joined:
    Jan 21, 2014
    Messages:
    662
    Location:
    Niers, Germany
    Thanks for the hints, info and advice.
    The flat gasket has 2mm. Will see if i have 3mm in the spares.

    But i have the impression that the leak is somewhat different....

    I couldn't see any cracks. But few scratches in the filler cap, where the gasket is put.
     
  10. bp4willi

    bp4willi Germany Subscriber

    Offline
    Joined:
    Jan 21, 2014
    Messages:
    662
    Location:
    Niers, Germany
    @Henry Plews
    It has sprayed on "BUND".
    Need to check for numbers...
     
  11. podbros

    podbros United Kingdom Subscriber

    Offline
    Joined:
    Dec 27, 2015
    Messages:
    1,618
    Location:
    Wirral
    Ah, ok.. well if you clean the top gently with a brass wire wheel or wire brush to get rid of any dirt so the finish is brighter?
    Then heat Carefully and briefly ... You know what I mean?? !!!

    If there are any cracks the heat will open them slightly and oily residue will reveal them..

    But be Very Careful!!!

    Or you could use a spray.. Crack and Leak Detector spray for welding?

    but heat is best
     
  12. bp4willi

    bp4willi Germany Subscriber

    Offline
    Joined:
    Jan 21, 2014
    Messages:
    662
    Location:
    Niers, Germany
    @Henry Plews
    No numbers stamped on the tank nor elsewhere.

    @podbros
    No dirt in the filler cap. Cleaned up with alcohol. Added some very liquid cyanacrylat glue, to fill any small scratches.
    Next test tomorrow.

    Should i heat up filler cap when tank pressurised?? Doesn't it damage the gasket?
     
  13. podbros

    podbros United Kingdom Subscriber

    Offline
    Joined:
    Dec 27, 2015
    Messages:
    1,618
    Location:
    Wirral
    Hi,
    Sorry I meant to gently heat the threads on the tank filler , my fault for not being more clear :doh:

    I am sure your method is safer :thumbup:

    If you think the filler cap is at fault I am sure someone here would be able to supply a part for it?
     
  14. Graham P

    Graham P Australia Subscriber

    Offline
    Joined:
    Mar 3, 2012
    Messages:
    903
    Location:
    Albury area NSW AUstralia
    I have an AL21 Marked Bund Z/B 8273 which appears the same, but pump tube is brass(nickel plated) your pump appears to be aluminium as do its fittings.
    Try some soapy water around the tube collar area with tank pressurised ..
     
  15. bp4willi

    bp4willi Germany Subscriber

    Offline
    Joined:
    Jan 21, 2014
    Messages:
    662
    Location:
    Niers, Germany
    Thanks for finding the cause.
    The hint with soapy water was excellent.
    The gasket was not causing the issue of pressure loss.
    I discovered, the joint from tank to threaded filler fitting was leaking.
    I had to solder this.
    Soldering with gas torch of course damaged the colour.
    But now it holds the pressure.
    IMG_20210216_225739.jpg
     
  16. primaxel

    Offline
    Joined:
    Aug 31, 2017
    Messages:
    76
    Location:
    Germany
    @Graham P
    AL21 Marked Bund Z/B 8273 = ZB = „Ziviler Bevölkerungsschutz“.
    Lamp was used at THW (Technisches Hilfswerk), Fire Department, Red Cross or another Zivil organisation.
    :thumbup::thumbup::)

    Regards Frank
     
  17. bp4willi

    bp4willi Germany Subscriber

    Offline
    Joined:
    Jan 21, 2014
    Messages:
    662
    Location:
    Niers, Germany
  18. primaxel

    Offline
    Joined:
    Aug 31, 2017
    Messages:
    76
    Location:
    Germany
    :thumbup::thumbup::thumbup:
    running welk!!

    regards Frank
     
  19. Fireexit1

    Fireexit1 United Kingdom Subscriber

    Offline
    Joined:
    Jun 13, 2020
    Messages:
    792
    Location:
    Brighton UK
    Good repair work !
    C
     

Share This Page