MrLexse

When I tried to flush the downstream lines from my PSD pump, I took apart the slave cylinder to check its condition. This is what I found.
Are the blue seals in the slave cylinder supposed to be continuous rings (like "O" rings) or are they designed with breaks in them (like cylinder rings)? I only ask because the breaks are so clean and angled that they seem intentional. Assuming they are supposed to be continuous, and these are gone, are there replacement rings available, either in a re-build kit or separately?

ROG100

I can't answer your question about the rings but there is not a rebuilt kit available for the PSD slave as far I know.

NoVector

I thought the same thing--they're like a 30 degree angle. The guy who figures out what replacement rings fit is going to be very popular someday.

AO

I would say they are supposed to be continuous. As I look at NoVectors pic, ou can clearly see the bottom seal is about to give. They look like some kind of nitrile o-ring but I have no clue what the spec is. I would assume some other slave rebuild kit might work?

Curious, what made you take this apart? I would think this could be a problem for any of us with PSDs.

928 Loon

Mine had the 30 degree angled ends as well. I assume this is the way they are designed.

Mine was shot because the pin was seriously corroded and about 5-10 mm shorter. Also, the cylinder was pitted inside. I'm not sure how this happened but it was IMHO unsalvageable. I don't see why you couldn't repair the one you've taken apart as it looks pretty good.

FYI, a replacement for these bad boys is about US $400. which is a shocker.

Cheers, Cameron

MrLexse

I did a forum search and came up with another picture of a "split" ring with a similar looking split (30 degree) ends. The middle one is different than either of the outside two and appears more like an "O" ring. I haven't seen one of the middle ones split yet. I'll take the $400. gamble and reassemble the piston with the split end rings and see how I fare. It's easy enough to get to and replace later, if it doesn't work out.

MrLexse

On second thought, before re-assembly and re-installation of the slave cylinder, I think I will look into the possibility / availability of a generic replacement ring. The challenge is to get a seal that can stand up to the hydraulic fluid pressure generated by the PSD (180 bar-2500 PSI). Anyone have a suggestion?

Jim Devine

Should be some help here if you want to dig a little...

http://www.physics.harvard.edu/servi...g_handbook.pdf

On page 4 it says they can make any "O" ring -
Call them & send a sample- might get lucky

AO

I will ask Tim Murphy this weekend. He works in Hydraulic Power and may have some insight. Also know some guys over at Bosch that might be able to lend insight, but they work in braking which is a bit different.

MrLexse

Jim Devine-
From page 196 in the O ring Handbook: seems as if the end seals (back up rings) are supposed to be split, as it describes the application very accurately.

Tom in Austin

Amazing what we learn here on RL! Makes perfect sense now that back-up rings on either side of the solid one are used to manage the pressure acting on it. Wonder what the science is about the size and offset of the gaps?

I am looking forward to the specs we end up with so everyone can replace the old ones on their PSD piston.

MrLexse

Okay, I went to http://www.epm.com/. They offer to size replacement seals and determine the material they are made of, if the original seals are sent to them. I Emailed them, describing the seal "environment" (automotive brake fluid @ 2500 PSI) and asked if they would accept the entire piston with the seals in place. If they will, I'll send it. If things work out, they'll be able to identify suitable replacements for the OEM seals, and we'll have a source for "rebuild" seals going forward. I'll let you know what happens.

AO

Lex... If you send them the piston with seals, are you sure you will get it back? Be careful and diligent.

If they can match them, put me down for a set. I'm sure I will need them sooner or later.

Rob Edwards

Also happy to buy a set or three.

Dave928S

Put me down for a set too! I'm sure you'll find many more here are interested.