Problems with a Lelit Combi OPV

[Aaron]

My Parents have a lelit combi, badged as a Quaha Napolitana. It has been going strong for close to 20 years making a couple of coffees a day.
Just recently it has started behaving like there was not enough pressure to push the water through the coffee, no matter how lightly it was tamped or coarsely it was ground. I suspected the Pump, but before i pulled the machine apart I thought i had better check the OPV valve. Sure enough when i went to make a coffee, after I had switched on the pump, i opened up the water reservoir and found the water pouring out of the OPV discharge tube. So I am guessing the pump is fine but the OPV needs replacing. Does anyone see any flaws in my logic so far?
So my question to the greater snob community is, is this a normal thing? do these Valves fail? is it a case of just pulling it out and giving it a clean or is it not worth bothering with and i should just replace it?
I must admit i was quite chuffed that i could diagnose the OPV just by looking and hearing a description. (if indeed that is the problem)

[artman]

Sounds like a sound diagnosis. Are you getting decent volume from the group without a PF? This would eliminate a blockage somewhere along the way that could also activate the OPV. Run the pump with no PF and make sure you are not getting any flow through the OPV into the tank.

The OPV is just a rubber seal with a spring pre load. You should be able to unscrew it and see if anything obvious is causing it not to seal, there is not much to them. Not expensive to replace either.

Cheers

[Aaron]

Yes, when there is no PF water flows through the group and none flows back to the tank. so it looks like its the OPV, thanks Artman.
I was thinking, if i pulled the existing valve and managed to clean it, id have to recalibrate it when i put it back together right? That sounds like too much trouble for a $25 part that's 20 years old.

[artman]

Yes. But you should probably re calibrate with the new valve also. You could accurately measure distance/turns the valve is set at and reassemble to the same spot. Taking the old one apart is a good way to learn how they operate and would be interesting to see why it failed.

Cheers

[Aaron]

Well I bought a new Valve but when I received it, it is completely different looking to the one that is currently installed.
I will try and post a couple of pictures
Also, Artman, to recalibrate i'd need a pressure gauge and needle valve setup on the PF wouldn't I? I couldn't get a scace gauge as this is a weird sized PF. (and they cost nearly as much as the entire machine)

[TC]

It's pretty much always the way with the old Imat, Nemox, Mokita et al. My experience is that pretty much everything is subtly or significantly different.

Sorta like buying parts for a current commodore and then trying to fit them into a 15YO model

[artman]

You could just screw a pressure gauge to the PF where the spout normally sits to calibrate your pressure. Not having any flow won't make it exact but it will be close enough.

Cheers

[Aaron]

Here's some pictures of the OPV in place - its nestled all amongst a heap of wires so its hard to take a photo.
I have also included a shot of the replacement OPV which i ordered.
The opv is attached directly to the out-flow of the vibe pump. The white nylon pipe you can see in the first pic goes to the boiler and the top of the OPV has had the bypass pipe that flows back to the reservoir removed.

[Aaron]

I understand there are a lot of variations in these units, but fundamentally are all OPV valves equal? meaning as long as it can be made to fit somewhere inline between the pump and the boiler, all of these various opvs will do the same job regardless of their shape right?

[artman]

Yep that is correct. Essentially they are just a spring preloaded bleed valve, that's my understanding.

Cheers

[Braithe]

Hey guys
Believe it or not I too picked up a Mokita Combi (same as Lelit but older). It's the older 57mm portafilter model (I believe they upgraded?), which is a pain but anyway.
The grinder is quite fine for what I'm used to, however it doesn't like it that fine. It needs to be on about 6, and then it will take some tamping. Otherwise there's not even a drip and the water gushed back when the brew switch is turned off.

The previous owner obviously didn't know about the drain pipe into the drip tray (Gaggia Classics have the metal tube, this has some obscured plastic tube), and subsequently most of underneath the trip tray is rusted.
But I'll have a crack at checking the OPV; have adjusted my Classic's heaps so I hope it's as pain free.