Riviera leaking past piston seals - Page 2

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
User avatar
peacecup

#11: Post by peacecup »

The piston rod is inserted somehow on these machines, and it might be possible to remove it, cut it, and re-thread it. Or does it need to be longer? In that case replace it with a new one - should be possible to source a steel bar that diameter, thread it and bore it.
LMWDP #049
Hand-ground, hand-pulled: "hands down.."

pizzaman383
Supporter ♡

#12: Post by pizzaman383 »

Is it possible that the pistons aren't the original dimensions? The locations of the seals, the water feed hole(s), and other dimensions is critical. I can't see how wear and tear could cause the hole/seal alignment problem you have. You may need to machine new pistons.
Curtis
LMWDP #551
“Taste every shot before adding milk!”

RobAnybody

#13: Post by RobAnybody »

this particular machine has a bit of a history which may explain one or two things:
Riviera Two Group piston seal problem
LMWDP #647

User avatar
cuppajoe (original poster)

#14: Post by cuppajoe (original poster) »

Yes, this thing has been a PIA from the beginning. Someone has got to it and apparently had no idea as to what they were doing, so I have no idea as to what's been done and what parts have been used.

Here's the situation - The distance from the screen to the inlet port is 17mm and the distance from the bottom of the piston to the top of the middle seal is 19mm. So with the piston at rest and the face of the piston just shy of the screen there is no way for the inlet to be above the middle seal, so no way for the middle seal to do its job. The distance from the bottom of the piston to the middle of the spacer between the middle and upper seals is 22mm, so the inlet needs to be about 3mm higher.

There is no way to shave enough off the bottom of the piston to solve the problem. I've checked these measurements against another group and it was within 1mm. If these are within factory spec, I'm surprised they don't leak out of the box. Zacconi does not have a three seal piston listed, nor other spring group parts. The spring machine was discontinued for awhile, but is now listed in their catalog. Hopefully this indicates they will start offering parts.

If no other solutions show up, my last ditch effort is to try adding another layer of teflon tape behind the middle seal. So far I've not found a source for a thinner seal.

Thanks again.
David - LMWDP 448

My coffee wasn't strong enough to defend itself - Tom Waits

User avatar
peacecup

#15: Post by peacecup »

I thought these groups were identical to the Ponte Vecchio/Sama three-seal groups. If you upload of photo of the piston with the measurements I can compare it to mine, and see if a PV piston would fit correctly.
LMWDP #049
Hand-ground, hand-pulled: "hands down.."

User avatar
cuppajoe (original poster)

#16: Post by cuppajoe (original poster) »

Thanks for the offer, I'll disassemble a group. So far I've been working with groups from other machines. I've had the problem groups apart eight times, so have been trying to avoid another round.
David - LMWDP 448

My coffee wasn't strong enough to defend itself - Tom Waits

RobAnybody

#17: Post by RobAnybody »

you might be on to something! the ponte vecchio piston does look a lot like the pison in the riviera!
here's a picture of the PV piston from lamacchinadelcaffe.com
if you compare it to the original posted earlier:


hopefully the dimensions also match!
LMWDP #647

User avatar
cuppajoe (original poster)

#18: Post by cuppajoe (original poster) »

Here's the piston. Apologies for the draftsmanship, straight lines with a trackball are impossible.
David - LMWDP 448

My coffee wasn't strong enough to defend itself - Tom Waits

miab

#19: Post by miab »

The water inlet into group must be above middle gasket on piston when at rest. You made an adjustment where the piston sat right in the bore but you say it is too low where shower screen is. Did you mean the bottom gasket protrudes out bottom? If not but it hits shower screen loose then get deeper shower screens. If it just puts pressure on the shower screen but doesn't knock it out then that is actually the ideal scenario.

Maybe a shim where piston rod screws into piston and deeper shower screen is best.

pizzaman383
Supporter ♡

#20: Post by pizzaman383 »

How far up from the bottom of the cylinder is the water inlet hole?
Curtis
LMWDP #551
“Taste every shot before adding milk!”