Does the profile of the center part of your pump that hold the pistons look like this?

http://i54.photobucket.com/albums/g8...g/o-ring-1.jpg

If it does, you might be missing a O-ring. You may have a different model of pump. As I mentioned, my pup did not have the flat seal on top (red) so others who open their SLS pump up and see a standard O-ring on the top may have a pump similar to mine which does require a o-ring on the center portion that hold the pistons.

It's been a little while, but if memory serves, then yes, it looked like that. Are you saying there are FOUR o-rings in your pump along with the shaft seal? My pump had THREE o-rings and no shaft seal. Removal of each of the individual pistons from the hub was not necessary to access any of them. I did remove the whole piston/hub assembly in order to replace two of them. That red seal WAS originally a typical round o-ring. It was just flattened from time. I think there is a semantic issue going on in this conversation.

I thought there were there seals plus shaft seal but looking at your break down I think there may have been four. One seal for the two halves (you do not show the top part of the pump in your pick but IIRC there was a grove for the seal). One ring on the bottom of the back housing in the groove along the outer edge of the 'bowl' (bottom right of your pic) under the steel piece that holds the pistons, one around the steel piece (black thing on top part of my pic) and one on the top part of the steel cylinder that hold the pistons (see groove on top in your picture).

All I know for certain is there was a O-ring on the steel cylinder (top in my picture) and under that cylinder that required the removal of that cylinder.

When I rebuild the spare I'll document it better because now you have me curious..

That piece you show IS the part I am calling the hub and contains the four pistons. Yes, I removed the hub and replaced the two o-rings (the one around the hub that you show pictured and the one behind it) as I described in detail in my posts.

http://i13.photobucket.com/albums/a2...bybapa/Duh.jpg

See the steel ring with the big red arrow pointing to it? It is not necessary to remove the steel ring from the center of the hub and remove the four pistons individually from the hub and doing so just adds work.

OK, I get it now.

How did you get the center assembly out with out removing the pistons? I saw where you were talking about a flat surface and a piece of wood but mine was in their tight. I had to use a dowel in the piston holes to pry it out.

I had a piece of wood on the cement floor, flipped the pump over so that the hub was facing down toward the wood and smacked the pump squarely against the wood. Because the hub weighs a fair bit and is recessed deeper than the aluminum case, that creates quite a bit of force to pop it out. With it flush to the case, it was loose enough to just fall out from it's own weight. If it is still stuck, then I imagine one could use two pieces of wood so that they are staggered on either side of the hub so that it has more room to pop out. Of course you'd want to make sure the hub could fall onto something soft so it doesn't get marred.

Hi,
I changed the O-rings last week, I found 3 of them. I agree that two 2mmx63 and one 2mmx53 do the job. I just measured them with a caliper, called a local hydraulic outfit and got them picked up by somebody who happened to be passing.
I paid less then 10 euro for the rings, used silicone in place of the paper gasket, had it off, repaired, refitted and bled inside 30 minutes. This is a very simple repair, just remember to treat your 1200 dollar piece of aluminium with respect!