Well, I may have spoken too soon. The one thing about this that wasn't adding up was the fact the pump goes to 9 bar, then clicks and gets quiet (but is still vibrating), and pressure falls down to 4 bar. Then the pump gets loud again and builds to 9 bar, clicks to quiet, down to 4 bar, etc.
I started thinking that the difference in pump noise might be related to the pump being under load or not, which led me to wonder whether the OPV was malfunctioning. All I could think was that the OPV was opening at 9 bar as it should, but instead of moving open gradually, maybe it was opening and not able to close again smoothly enough to keep pressure at 9 bar? This still doesn't make total sense to me, but I pulled the OPV apart nonetheless. The moving part (spring and rubber seat) was not crusty, but the rubber seat was deeply dented where is seals against the brass tubing inside the OPV. On a hunch, I pulled the rubber seat and flipped it over, effectively giving it a new face to seal with. I am still waiting for the machine to warm up again, but initial tests are promising--the blind filter disc will hold 9 bar without losing pressure, which it wouldn't do before the switch. I know that I changed the OPV one time previously with the pump switch, and I'm wondering whether perhaps this was a coincidental fix that looked like pump failure. The other times, I've changed the pump and that has cured the same symptoms--I wonder if anyone can give a logical explanation as to why a pump switch might help overcome a malfunctioning OPV, i.e. with the seat deeply scored? Partly I'm wondering whether it was just coincidence, i.e. the seat might have gotten cockeyed across the brass tubing, and in the process of replacing the pump and readjusting the OPV the seat got straightened out. I still have all my old pumps so perhaps I now have a collection of spares. If in fact this is the solution, it might be a boon for the list, since I see this problem pretty frequently. Replacing the seat would be very simple, since the adjustment screw (and spring/seat) can be removed from behind the drip tray, without even removing the outer cover. I wonder if the seat is available by itself as a spare part? There really is nothing else in the OPV that could fail, as far as I can tell. Maybe a couple of o-rings, but those are easy and not common failures anyway. Thoughts? Best, bmc -- You received this message because you are subscribed to the Google Groups "Brewtus" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/brewtus?hl=en.
