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 ?
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...
I tried as well with a flat gasket, shown in last pic. How is Filler cap and pump tube connected? Screwed, soldered, pressed??
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 ???
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...
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
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.
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
@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?
Hi, Sorry I meant to gently heat the threads on the tank filler , my fault for not being more clear I am sure your method is safer If you think the filler cap is at fault I am sure someone here would be able to supply a part for it?
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 ..
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.
@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. Regards Frank
