so which part are you talking about ?
Hey Guys, Ive had my VBM *Domobar Super for a couple of years now, its an awesome machine and has been very reliable. Recently I noticed when I filled it up again that there is a light hissing sound. I opened up the unit and had a good look around with a torch, but could see nothing wrong. The hiss seems to be coming from an attachment to the boiler but there is no visible steam being released. I used to have it on a timer but have left it on permanently for the last year. I back wash with a citric acid cleaner monthly and it has never given me any problems I seem to be refilling the water container more often so there must be a leak somewhere!
Any thoughts. I would hate to be without it for a few weeks to get it fixed. Is there anything I can try myself?
so which part are you talking about ?
My guess is 9. My VBM was hissing from there after transport and it just needed a tap to reset it.
Had my VBM for only a couple of months now, and it hisses each time I fire it up as the water in the boiler reaches its operating temperature, it seems. Doesnt seem to cause any hassles with ours.
9 is OK...Originally Posted by 726E781A0 link=1280897967/2#2 date=1280900157
Sounds like 9 the anti Vac valve..Originally Posted by 4D75756A7F7F1A0 link=1280897967/3#3 date=1280921873
If from any where else... Then it needs to be taken for a service...
Mind you the Anti Vac valves to grunge up and can get that bad they do not seal when they should..
Then it needs to be taken for a service ;)
First, there is no need to "back wash" (aka backflush) with citric at all. Citric acid is used to descale- remove of mineral deposits from the boiler, HX, and related piping. You can check for mineral buildup by removing the mushroom (remove the two socket head screws on top of the group and remove that assembly). Even then, there are better alternatives to citric acid which is not as effective and the commercial products made for the task.
If the hissing is constant then further investigation is necessary. if it is only when yo tun it on after it has begun to warm up for two or three minutes or so, then stops, this is the anti-vacuum valve and that behavior is normal.
Thanks for the info. Now if I could only improve my coffee making skills...
To summarise and explain further:
a) Most likely cause of hissing is the anti vacuum valve. It should only splutter and hiss when the machine is turned on from cold, and before it has seated properly during warm up. Hissing from any where else requires you take it to your local servic agent.
b) anti vacuum valves can be reset by giving them a tap while the machine is pressurised...which necessitates removing the top plate from the machine exposing other internal parts including wiring. *If I were to effect this service, I would switch machine on until fully pressurised, then switch OFF and pull the plug from the electric socket so there is absolutely no possibility of live electricity in the machine. I would then remove the top to get access to the valve.*Simply switching off the machine is not good enough as it leaves electricity to the main switch (if not somewhere else) in the machine. After that has been done, I would tap the nipple of the anti vacuum valve with something hard to force it to reseat itself. Unless the valve is worn, it should then stop leaking. Sometimes more than one tap is necessary.
I am VERT CAREFUL in doing this, as every time the nipple is tapped and reseated it will release steam pressure for a second and the last thing I want or need is a steam burn to my hands, arms or face
After this is done I put everything back together properly and resist the temptation to fiddle...before switching the power back on.
Leaving your machine on 24 hours allows it to cycle ad infinitum and wears out components by cycling them to the end of their designed in working life even though the machine is not being used to make coffee.....ie it is wearing out while just sitting there doing nothing waiting..... The first thing to go will be the pressurestat particularly on machines that use the smallest cheapest miniature pressurestats with 2 cent microswitches without relays. Clients always say...."but the machines hardly ever made any coffee" !
In agreement wth Randy, backflushing the group with a descaling agent is a waste of time. Not only....but it could possibly be damaging to some internals of the valve due to its acidic (therefore corrosive) nature. *Use only a proprietary group flushing detergent, as the function of back flushing is to strip out oily deposits that eventually block up the valve and stop its proper function, not scale.
Hope that helps,
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Originally Posted by 1F2B3C2A31061A363F3F3C3C590 link=1280897967/7#7 date=1280963189
i like to tap my nipples with a long wooden spoon when needed :)
If that doesnt work, when the nipple is cold, hold it firmly between the thumb and forefinger and while pulling on it, give it a little slow twist. This reveals any grittiness... :oOriginally Posted by 78747D707079150 link=1280897967/8#8 date=1280970651
Bloody hell.... spluttered while drinking a coffee, now I have a mess to clean up.Originally Posted by 30030C061B3D254C620 link=1280897967/9#9 date=1280976600
RandyG you got to stop that...
I think something other than a leaky nipple is your issue there AM ;)Originally Posted by 5F70797B6C537F707F797B737B706A1E0 link=1280897967/10#10 date=1280976880
If tapping the valve reseats it and stops the hissing, then its only just started to leak and will be rebuildable. After taking the necessary precautions to avoid burns (let the machine cool right down), undo the top of the valve (17mm spanner) and pull out the brass plunger. Theres a teflon seat that comes out with the plunger, and an O-ring (generic size 007) that does the sealing. Replacing the O-ring, which will have perished due to the heat, should fix it nicely. Use a viton O-ring to ensure it lasts. If it has been leaking for a while however, the teflon seat will have eroded slightly due to the corrosive nature of steam, and its likely that the valve will start to leak again soon despite the new O-ring. In that case youre up for a new valve, which from memory only runs to about $18 anyway.Originally Posted by 0B3F283E25120E222B2B28284D0 link=1280897967/7#7 date=1280963189