Piston rod adjustment

pinzinator · Post by **pinzinator** » Sun Jan 25, 2009 9:36 am

I rebuilt the master cylinder in my 710M using the factory kit, and now the front brakes don't seem to release all of the way, despite the shoes being adjusted all of the way back. The shoes have less than 1000 km. The repair manual states that the piston rod should be adjuted to 1 mm clearance, which maintains a neutral position of the pedal, I assume. The book does not say how to make this adjustment, does anyone know how to do this? Does the master cylinder need to be removed to do so? While installing the master cylinder I did not notice that the rod began compression of the MC piston before tightening the 2 mounting nuts, everything seemed OK. If I bleed the front brake line at the master cylinder the brakes release slightly. The brakes springs are new and correctly installed.

Jim LaGuardia · Post by **Jim LaGuardia** » Sun Jan 25, 2009 7:26 pm

Sounds like you have a sticking/plugged residual pressure check valve.
They are located at the beginning of the brake line below the master cylinder.

pinzinator · Post by **pinzinator** » Sun Jan 25, 2009 7:40 pm

Jim I just took the Pinz down off the jacks a short time ago. I went over everything again and discovered that I did not have the brake shoe return springs intalled correctly after all. I have no idea how I got it wrong when I installed them recently, as they barely pulled on the shoes. No damage, just a lot of dust. The rears never were a problem. Your suggestion of a check valve makes sense, I agree. The brake pedal has a little slop to it before engagement, so I don't think the piston rod adjustment is an issue.

Jim LaGuardia · Post by **Jim LaGuardia** » Sun Jan 25, 2009 8:01 pm

Thats good because to adjust the rod, you have to remove the pedal block assembly

pinzinator · Post by **pinzinator** » Sat Feb 07, 2009 12:06 pm

The problem turned out to be something internal in the rebuilt master cylinder, something would not release the pressure to the front brakes over time. A very competent mechanic rebuilt it, so I would rule faulty workmanship out. It was a factory kit, so who knows? I bought a new master cylinder from EI and now everything works as normal. Looking back, I would not rebuild any brake componants again, just buy new. Also, when buying a new master cylinder you may want to consider buying a new reservoir, especially if yours is starting to show any age.