The valve just before the OPV is the pump priming valve. That valve and the OPV are tee'ed together and lead back to the reservoir on Quickmill machines and others I have seen. But who knows what has been done to your machine prior to your ownership. In any event, I would lead the OPV back to the tank and let the priming valve discharge into the drip tray or tee them together and go back to the tank.

The OPV also serves as a thermal expansion valve and will drip as the machine heats up - momentarily.

Your OPV is screwed down waaaay too much. You may have bottomed out the spring.

Yeah...I took it apart earlier and lubricated the o-ring. I screwed it down to lubricate inside the valve...took a phone call in the middle of it and forgot to go back and loosen it.

Since you knew the o-ring...would you happen to know the part numbers for the two springs in the OPV?

To the best of my knowledge, they are NOT available as singular parts. Why not simply replace the o-ring?

The one spring below the white plastic adjuster holds a glass ball against a seat. The only other spring the OPV contains (to the best of my fading memory) is a check valve spring in the discharge port. The OPV adjusting spring has a free length of a tad over 0.50". I'm not saying these springs can't tire out but I'd stick with the o-ring first and hope that my AS number is correct.

Oh...I plan to replace the o-ring tomorrow. I took the valve apart and lubricated the old ring waaay earlier in the day...before you joined the discussion.

I'm also thinking about plumbing in a gauge for brew pressure too...but still wading through all the info on the subject.

Ok...I worked on the machine over the weekend as time allowed. Here's what I've done...

1. Replaced o-ring on OPV set screw.
2. Cut the plastic water line leading from the OPV and into the boiler, added a tee, and installed a pressure gauge.

I finished everything up last night and the good news is that I am now leak free. However, something still isn't right because it is taking quite some time for the pump to fill the boiler and I'm only getting a trickle of water out of the group head.

This wasn't the case when I first plugged in the machine after finishing my work. I ran the machine several times with no PF to check for leaks and to make sure everything was working properly. Everything seemed to be ok...so then...I tested the machine with a blind basket to make sure the machine wouldn't leak when under pressure. I ran the machine with the blind basket 3-4 times. Each time I tested with the blind, I would then remove the PF and flush a bit of water through the group before going back to the blind. After the 4th time testing with the blind, I tried to flush the machine again and nothing but steam came out of the group. Then, I ran a bit of water out of the hot water dispenser to force the pump to come on and fill the boiler. I ended up having to turn off the machine because the pump ran for about a minute and still hadn't filled the boiler. Just FYI...the reservoir hose was not stuck to the side or bottom of tank...and yes, I am using the in-tank water softener. However, I removed it to make sure it wasn't part of the problem...removing it didn't change anything.

What's going on...I don't understand why the pump isn't filling the boiler or why I'm only getting steam and a trickle of water out of the group head?

Any thoughts or suggestions would be greatly appreciated!

If the pump is trying to fill the boiler but runs for 60 seconds, either your fill solenoid is not getting the voltage it needs to open or the fill solenoid valve is stuck closed. Disconnect and tape over one of the heating element leads to prevent power from reaching the element.

Check the water level in the boiler with a small wooden dowel through one of the fitting on top. Level should be around 2/3 full when all is well.

Ok...if the fill solenoid is stuck in the closed position...and assuming the pump is working properly...Wouldn't the OPV be diverting water back to the water reservoir?

I would assume that, if the pump is pumping properly, the back pressure from the closed/stuck valve would result in water being diverted back to the reservoir. If that is true, something else is causing the problem because there isn't a drop of water being diverted back to the reservoir.

???

. . . because there isn't a drop of water being diverted back to the reservoir.

Yes, you are correct.

You do understand that "filling the boiler" and "filling the grouphead" are two different hydraulic circuits?

Your newly installed pressure gage should read around 2 bar when trying to fill the boiler and around 4 bar when simply flushing the grouphead. It does seem as though the pump is simply not pumping. I would check that water level in the boiler real soon and perform any further troubleshooting with the heating element disconnected.

You do understand that "filling the boiler" and "filling the grouphead" are two different hydraulic circuits?

Yes...I do.

Your newly installed pressure gage should read around 2 bar when trying to fill the boiler and around 4 bar when simply flushing the grouphead.

Yes...as best I can remember those numbers are essentially what the pressure gauge was reading when filling and flushing...prior to the tests with the blind pf. After that 4th pull with the blind, the gauge was reading 0...even when the pump was pumping to fill the boiler. No pressure in the lines at all.

perform any further troubleshooting with the heating element disconnected.

Good point...will do.

So what could have happened to cause the pump to suddenly quit pumping? Air lock maybe? I did not over stress the machine when testing with the blind. I didn't allow the machine to run any longer than a typical backflush.

Any thoughts on how to fix?

Fill the pump's suction line with water using a "turkey baster" or similar device. Assuming this is the original pump, the seals and little parts inside may be tired and a replacement may be in order. I would keep an eye on the pressure and, assuming the turkey baster "trick" works, measure the free flow from the grouphead - should be AROUND 450 ml/minute.