Master Cylinder

Greetings!
New to the forum. Love it! I did look through some previous postings on master cylinders and didn't really find what I was looking for.
Here goes...
I have a '69 CJ5 w/ a Buick 231 V6 and very recently did a drivetrain upgrade. Replaced the Dana 27 w/ a Dana 30 and replaced the off-set Dana 44 w/ a larger center pumpkin 44. The brake size went from 9" to 11". I am having to double pump the brakes in order to stop and it will not hold when on an incline. I thought that maybe the MC is bypassing from the posts I read but wonder if I need a proportioning valve. Any thoughts?
Thanks!
Pete

 

A proportioning valve just sets the front-to-rear fluid volume ratio, so the rear brakes don't lock up, and the fronts get more action. Have you adjusted the shoes so they drag slightly 360 degrees when you rotate the wheels? Wheels should still roll free, but with shoes just touching.

 

I think the double pump could be from two different things - (1) your mc is shot (bypassing, leaking) or (2) your mc is not large (volume) for the disc brake calipers. I've got the dana 30 front end with discs and it's great but I do sometimes need to double pump. It will hold on any incline so I suspect that you may still not have thing adjusted up enough or things aren't quite "warn in" yet.

I would recommend the proportioning valve - it can help set the front/rear balance.

Do you have the single or dual mc?


1970 CJ-5, 225 V-6, headers, HEI, PS, D30 Fr, 44 Rr, ARB's, SM420 w/ Novak, D18 twin stick, 33" TSL Radials, Ramsey REP 5000, Sky Jacker Soft Ride,

 

Hey-I will first adjust the rears to see if that helps...thought they were self adjusting, like when you back up a (Ford)
I've got the MC that mounts on the frame rail, dual cylinder, has a bolt that holds the cover on, the one that costs the most! Do they charge so much for the bolt?!?

 

Think I found the problem. The pasenger side wheel cylinder looks like it is leaking and one of the hard lines coming off of the rubber brake hose is too.
What's weird is I checked the fluid level in the MC and both sides are down about half. I don't see any leakage coming out of the front. Would bypassing cause fluid to go from the front half of the MC to the back half? Will I still need a new MC if I get the leak fixed? If not, can I use one from a newer clamp lid style?
Thanks

 

I'd fix the problems you found and then look very close at the rest of the system also.
Have someone pump the pedal while you look for other small leaks.
Wear some eye protection too. Brake fluid meets eye = pain.

 

What they said, x2. Get the basics fixed first, then re-evaluate. Re: "self-adjusting brakes" - most drivers don't realize that to advance the things only one click, you need to reverse at speed, and darn near jerk your neck off in a hard stop. I guess that the engineers figure that you will jerk to a stop in reverse every now and then.

 

Thanks guys for the info!
I probably won't get to looking at the system for a while but when I finally do resolve the problem I will post a reply.