Brake Master Cylinder rebuild?

Trot

Trot

New member
Howdy all,

I'm going to be tackling the annual on my 260 (once the dust settles after closing on a house and moving in). In addition to the usual annual stuff, I'm thinking of looking into rebuilding or having someone rebuild my left brake master cylinder. It works, but it's soft and sometimes takes a pump or two to stiffen up and grab. I'm thinking it might just need a new O-ring set and refilled. The area around the pedal on the wood floor panel shows evidence of a very minor seepage.

Anybody know where to find any information on these old Paramount master cylinders? I can not find anything online and I've been looking for months. I think the model numbers are either VHR-15-750 or VHR-15-625. I can't get a good look until I pull it out.

Also these brake calipers are unlike any I've ever messed with before. Attached are some pictures I took. Normally there is a filler tip to pump fluid from the bottom up, but these don't have that. Anyone ever messed with these before and know how to service them? The Cleveland sticker on it says it's date of manufacture is March 1969, and model number is 3000-250.

Thanks in advance all, any help is much appreciated!

-Trot
 
those are symptoms of air in the system.. so new O-rings, flush and refill, bleed.

nothing is ever easy.
 
Just a comment Trot - that is a rather non-standard safety wire installation, usually reserved for castellated nuts where the safety wire goes over the top or used in minimum clearance areas. Not being critical, just an observation.

art
 
No, I never found the exact match to what my bird has. I just keep refilling the master cylinder on the left brake and watching close to make sure fluid doesn't leak out and ruin my carpet. Someday I'm sure I'll have to retrofit more modern master cylinder pedals but right now I'm a broke corporate jet pilot so that upgrade will have to wait.
 
I had VV-15-625 cylinders in my Cruisair. They were from a Bonanza I think. Anyway, I did rebuild a few of them. Some parts are available, however, the o-rings are standard MS (or AN) parts. Check out:

http://csobeech.com/files/Bonanza-Deb-MC-Overhaul.pdf

Larry Lowenkron
 
the bleed screws work different than modern ones, there's no nipple and no valve. you have to take an approriate size and thread machine screw and cut the head off and drill a tiny hole down the shaft. take off the plug screw, screw in your new brake bleeder tool and screw it in, put the hose of the 8606 pump over the screw and pump away, just don't pump too much so the master cylinder overflows or the pump reservoir gets low and you start pumping air.

when you reverse the process to put the plug back in, be quick. the less fluid you lose, the better. the process works amazingly well.

the way the master cylinders are built, if it's leaking around the shaft, just take it apart and find an o-ring to fit, and put it back together. if it's spongy even after the cylinder is bled, the other o-ring is leaking. if it needs bleeding, you can't really tell if you need o-rings. since they bathe in 8606, the o-rings last a really long time.

be sure to tighten the plug well, there is no way to safety it. and speaking of safety wire, when you are done, thread some safety wire through the hole in your brake bleeding screw and permanently attach it to your toolbox somewhere safe, where you can find it next time you need it.

just my opinion, your results may vary.

bobg
 
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