PS pump cylinder head O-ring seal.

[Bernie Benz]

Repost from <http://forums.audiworld.com/9080/msgs/431403.phtml>

Hi guys. Nothing better to do right now than lurk on this site.

Problem with the rebuild kit parts kit and my original O-ring size  
recommendation is that both were designed for the wrong interface  
seal surface under pressure. This O-ring under pump pressure must  
seal against the ID of bore in the pump housing, not the OD of the  
cylinder head. If the latter, the O-ring must be moved by pump  
pressure to seat against this bore ID, Not a good static seal design.  
Use a 2-019 rather than the previously recommended 2-018 generic o-ring.

Further, when reinstalling the cylinder head with a new O-ring, the  
ring must be well greased, not just with PS fluid, to prevent  
differential area elongation and resultant localized cross section  
reduction because of the cylinder head rotation. This cylinder head  
need not be torqued beyond screwdriver tight to provide the required  
initial o-ring squeeze.