Hello this is a vibration pump model only 18mths old,

When I pull a shot the machine ramps up to 10.2 bar ( which is where I have set the OPV to ) now the pump keeps the pressure to 10ish bar give or take a little until I release the lever to finish the extraction all normal.

The problem I have is that occasionally when the machine ramps up to 10.2 almost instantly the pump goes to an almost silent humm and the pressure drops back to about 8 bar it seems as though the pump is not working as hard,the shot continues to pour at that lower pressure and the pump can hardly be heard pumping, after the shot I put the blind filter in same thing happens,run it 3 or 4 more times same thing,

Turn off machine let it cool, turn it back on after a couple of hours warm it up run a shot back to normal.

Now this happens randomly but does seem to only happen if the machine has been on for a number of hours has me thinking something is getting too hot,

I did mention this when I had it serviced but was told the pump is fine and they did not seem to understand the problem I was having,

Anybody out there know what this could be and why it's happening

Thankyou

MNSTA

Today I have pulled about 8 shots, ramps up to 10.2 pump tone drops to a near silent hum and the brew pressure drops back to 8 bar,this is happening every time now,

Any ideas ?

Sticky OPV, initially staying closed, then eventually limiting the pressure to 8 bar, is the likely culprit. Disassemble, clean, exercise the spring, reassemble.

Browse through this thread - Pump humming instead of vibrating? .

This situation has been brought up about a dozen times (that I can remember) and the easiest solution may very well be to replace the pump.

Thanks Jim I pulled the OPV apart took out the spring seemed to be nice and clean

Put it back together ran a couple of blind shots and it seems ok

I'll see how we go over the next week if the humming comes back I'll replace the pump

Thanks for the reply to eric may well be the pump.

Thanks

MNSTA

I read that this possibly could be caused by water getting to hot in the tank some pumps are only rated to a certain water temp this could explain why it only happens to me when the machine has been on for a number of hours,
Next time it happens I will take out the tank empty the warm water and refill with cold to see if it solves it.

MNSTA.

Ok this issue is happening when the water in the tank heats up

ran some shots this morning all ok then the pump did its humming thing again after the machine had been on a few hours and the tank water was warm, pulled out the water tank and refilled with cold water ran some more shots and no problem,

So the water getting warm is making the pump humm

Spoke to an expobar tech and he had never come across this problem

I am going to replace the pump and hopefully solve this problem.

Vibe pumps have a little plastic ball valve, a one cent part, that prevents back flow. If it deforms from overheating, you need to replace the pump, since there are no spares. That's been the most frequent cause of the demise of my vibe pumps, and, as Eric noted, probably most other people's.