Hi all, another question which I'm hoping may have a simple answer i've just missed! Apologies if this has been covered else where I had a look but couldn't find reference to this specific issue. I've been lent an original Optimus mini pump (and cap) which i intend to use with one of my Optimus 99's or 80's. It hadn't been used in many years so I intend to replace the consumables and have ordered the 2 replacement O - rings for it. However in the meantime I thought I'd give it dismantle it, clean it and give it a go! when I removed the pump end from the barrel there appeared to be residue of silicone (not a paste but of a rubbery consistency) on the treads. Before disassembly the pump was a little stiff but when it went back together all seemed well until it became apparent that it wasn't creating sufficient pressure for air to pass through the cap nrv. I did a dunk test with my finger over the end and sure enough it was leaking from the between where the barrel and the pump end meet. Upon inspection I've noticed that the thread on the pump end doesn't run all the way to the mating surface. it looked almost as if a third o-ring should be fitted there so I tested this theory out and it does indeed seem to solve the problem, my questions are: Did any iteration of the mini pump ever have a third o-ring? Or are these threads meant to have sealant applied to them when putting a mini pump back together? Or alternatively is this pump faulty in some way?
My used one is a little stiff, looks like some grease maybe on threads. My NOS is too tight to unscrew, so maybe just some grease and tightened good will resolve. Duane
Sure looks like it needs one, don’t it? It’s been many years since I messed with one, as I recall it included a packing.
Ah ok, so silicone sealant on the body is correct! Seems strange in a way as it looks as is there’s a gap for an o-ring. once the new pats arrive I will add a little of this to the thread in that case. thanks for your help!
Before you use silicone rubber or RTV on the threads, try some silicone grease and nip it up snug. I find that is plenty to make the seal and means easy dismantling again if need be Alec.
I believe this is the area the OP is talking about. You can see where he added an o-ring in the picture on the right.
Not necessarily, its a relief cut at the shoulder so it screws home against the body. They are generally a pitch-and-a-bit and just undercutting the root. Alec.
Maybe, but it leaks when screwed home against the body without a packing. Or goop. They were just cheap, it’s hardly a precision made product.
Indeed, the four I've dismantled had silicone or a loctite type compound that crumbled away. Don't over think it. Alec.
I tried using silicone grease instead of the o-ring last night and it certainly makes an improvement. I’ll do some more tests before I decide how to leave it set up. The o-ring set up certainly seams to work as well. thanks for all the advice, I’m also pleased to hear that my potential set up wasn’t to daft!
I have a small collection of these, two of which are unused. None have “packing” at the place in question in this thread topic. Tony
