if your talking about the cup that pushes on the pad, open to the pad, flat to the caliper. Otherwise it would take ALOT of brake fluid to bleed out with a giant void towards the caliper. Would probably NEVER get all the air out.

 

Nope not the one I'm talking about. I'm referring to the master brake cylinder. The rear brake pedal pushes on its innerds to make the brake pads work.
I'm thinking I need a new one, I put it all back together and its seeping a bit, I noticed last year it was wet there and thought it was coming from some where else.
Also if someone can give me the oem number for the rear master brake cylinder.

 

Well, my '86 uses a 41755-86 Master Cylinder. The rebuild kit is a 42374-86. That's probably all you need.

 

Thanks Dr Hess, what warrants a new rear brake master cylinder compared to just using the rebuild kit?

 

Flat part of the rubber cup goes against the piston in the master cylinder.

 

Perfect thanks John. Is there any special trick to installing the kit?

 

Kit came today and I installed it and bled as much of the old fluid out as I could. I also through in some new pads so I shall see how it works out.