My ECM Technika IV (a HX machine) uses a rotary vane pump plus a water tank (no direct water connection). I had somewhat too much drip from the expansion valve drain as described in the article "ECM Technika IV drip" (ECM Technika IV drip) by Keno (who seems to have the very same ECM model as I do). As this happened within my two-years guarantee, a service professional has adjusted the pump pressure (probably by adjusting the bypass valve). Result: the expansion valve drain did not drip any more and the pump pressure was reduced from 11.5-12 bar to 8.5-9.5 bar. So far so good.
After a few months I noticed the pump pressure was raising to 12 bar, but no drip from the expansion valve drain. To be obvious: in the meantime I did not adjust anything in the ECM: not the bypass valve, nor the OPV.
After having noticed this final 12 bar I adjusted the bypass valve through the adjusting screw at the bottom of the machine as has been advised in the original instruction manual (as well as on many other locations). I adjusted this bypass valve screw two full turns (720°), which is much more correction than I expected. Result: the pump pressure was reduced from about 12 bar to about 9 bar.
But after another month the pump pressure was raised again to 12 bar. I am fearing now that something in my ECM goes wrong and that it does not make sense to adjust the bypass valve again.
Possibly, the OPV is doing where it has been designed for: to act as a "safe release", which is a condition I would prefer to avoid.
Suggestions welcome, Leendert.

Unfortunately, I found no answers or suggestions on my question about the excessive high pump pressure. A high pump pressure: well possibly I can live with that, but since my former post the expansion valve drain is not dripping, but is leaving a steady flow of water (actually, much more water passes the expansion valve drain than arrives in the cup !).
So, I adjusted the bypass valve again (another full turn), as well as the OPV (for the first time: one full turn). Since my first action the bypass valve has got three full turns (1.080°) and my OPV one full turn (360°). Result: the pump pressure is 10.5 bar during making a shot (which I feel is not much difference from the initial 12-12.5 bar) and the ECM Technika IV is leaking excessively via the expansion valve drain.
I think this is beyond my level of understanding and I fear that there might be a failure in my machine that causes the high pressure plus excessive leaking. So unless someone has an advice, I consider sending my ECM to a qualified service center.
Suggestions welcome, Leendert.

Since my first action the bypass valve has got three full turns . . .

Then, the pressure adjusting valve (bypass valve) is sticking/stuck.

I would avoid, if at all possible, sending the machine to a service center. It would be much safer if you could carry it there yourself.

Dave and Eric,
Thank you for responding. The first few days I do not have the time to work on my ECM pump. Later I will see what I can do and I will update my experiences. Leendert.

The pump will be similar to this:

I dismounted the rotary pump (Fluid-O-Tech, CB054Z), I opened the balanced bypass nut (20), got in my hands the balanced bypass screw (22), bypass plunger (19) and spring (14). My pump does not have the lock nut (21).
I found nothing wrong, apart from the bypass plunger which is a little bit hard to move and the bypass nut has been turned out by me that much that the spring has no function (does not push) any more.
I am still where I was before dismounting the pump: much more water comes out of the expansion valve drain than arrives in the cup, in whatever setting of the bypass valve or the OPV. My best guess for what's going wrong: the firmness of the bypass plunger. I do not know whether this is the actual reason, nor whether I can simply put some grease on it.
I agree with Eric: "... avoid, if at all possible, sending the machine to a service center ...", but I want to arrive at a solid solution. One option (it might be exaggerated, but it is pretty affordable, about US $100) is to simply replace the Fluid-O-Tech pump. I found it pretty hard to turn my pump by hand, turning the pump with a screwdriver is easy. Turning the pump motor by hand is really a breeze.
Suggestions welcome, Leendert.

you need to pull the bypass valve (number 13 on the diagram above) from the pump body and clean it. what you have here is only mechanism that adjusts the bypass counter-pressure. just make it clean and lube the O-ring, nothing interesting to see there. move on to the valve...

I assume you put a light film of food-safe lubricant on the by-pass plunger o-ring.

If you end up replacing the pump, be sure to duplicate exactly what you have.

Thanks everybody for your help in learning how to dismount the Fluid-O-Tech, CB054Z rotary pump. I removed the bypass valve (or open valve, № 13) and lubricated (using silicone grease) this valve, as well as the bypass plunger (19) with the O-ring (18). Removing the open valve was pretty difficult, actually I damaged this valve a little bit.



Now, my ECM makes espressos on 9,5 bar, no water leaves the expansion valve drain while pulling a shot. So far, so good. But once I switch the brew group lever, it takes about 4 to 6 seconds for the water to leave the E61 brew group. I can understand that for the very first time, but this happens every time I put on the pump via the brew group lever. I do not know whether I should worry about it.
Suggestions welcome, Leendert.