So I think the bottom line is the question is about a proportioning valve.
Yes At low pressures (up to 500 psi) Fluid should flow freely in and out.
There is a company making rebuild kits for some proportioning valves - I have not noticed whether that includes the bendix


http://www.imperialclub.com/Repair/Lit/Master/233/index.htm

Last edited by Mattax; 05/26/20 11:12 PM.