• Welcome to the new SAOCA website. Already a member? Simply click Log In/Sign Up up and to the right and use your same username and password from the old site. If you've forgotten your password, please send an email to membership@sunbeamalpine.org for assistance.

    If you're new here, click Log In/Sign Up and enter your information. We'll approve your account as quickly as possible, typically in about 24 hours. If it takes longer, you were probably caught in our spam/scam filter.

    Enjoy.

Brake Master Cylinder issue?

Boobtube

Boobtube

Silver Level Sponsor
OK, I had my brakes all back together and began the bleeding process. What seems to have occurred is that the newly acquired master cylinder has a different depth for the push rod which is causing the piston to stay partially engaged and not allowing pressure release. This locks up the calipers and makes the pedal frozen. This MC came from British Victoria and it wasn't quite right when I got it. I had to remove a millimeter from the washer on the pushrod to get it to fit inside the cylinder and had to make a new spacer on the firewall mount to allow the slightly wider dust seal to fit through. The pushrod engages the piston partially when clipped into the MC. So now, I will acquire a new MC from SS but I wonder if removing the millimeter of the washer on the pushrod will be a problem. Will the circlip be able to keep it in place or do I need to get a new pushrod with a new washer(since it's all one piece)? Are they still available anywhere? I couldn't locate them.
I have learned my lesson with Brit. Vic.--good prices but nothing seems to fit. Their upper ball joints were oversized as well. You'd think if you are going to make replacement parts why not match to original specs.
 
Boobtube

Boobtube

Silver Level Sponsor
This was the original pushrod that I installed on the new master cylinder. It doesn't come with one. The portion before the bulge is long and pushes the piston in some when installed. I don't really want to grind down.
 
Barry

Barry

Diamond Level Sponsor
On my S-V, both the brake and clutch pedal arms have two holes for the clevis pin that attaches the master cylinder push-rod. There is probably a difference of 1-2" to 3/4" between the two holes and that can make a big difference in the effective length of the push-rod.

Don't know if all Alpines have the two holes for the clevis pins, but .....

Just my opinion, YMMV.
 
65beam

65beam

Donation Time
Boobtube said:
OK, I had my brakes all back together and began the bleeding process. What seems to have occurred is that the newly acquired master cylinder has a different depth for the push rod which is causing the piston to stay partially engaged and not allowing pressure release. This locks up the calipers and makes the pedal frozen. .
Click to expand...

You mention the front brakes are not releasing. Are the rear brakes releasing? If so then you have something holding pressure to the front brakes.
 
Boobtube

Boobtube

Silver Level Sponsor
Here is what I discovered. I didn't realize that master cylinders usually come with the push rod already attached. With the Brit vic MC, this was not the case and I had installed the push rod from my rotted original MC into this one. The problem is that the OEM push rod does not work correctly in this MC. It pushes the piston partially in all the time even in it's resting position. So 65beam, you are correct, the pressure is not releasing because of this piston never coming fully out. The rear brakes do release.
I figured out I have two choices, I can either cut down(shorten) and polish the front end of the pushrod that contacts the MC piston or get a correct MC from Sunbeam specialties. I decided to go with the SS MC because I'd rather just go with what actually fits right rather than having to modify everything.
Changing the portion that connects to the pedal would not alter the geometry that is within the MC that is held in place in front of the Circlip. Thanks all. It is a case of junk parts sabotaging my restoration. I suspect Brit Vic found a MC that was really for some other application and said, "hmm, close enough for a Sunbeam," when it really wasn't right.
 
Boobtube

Boobtube

Silver Level Sponsor
Got the new MC

I wound up buying a new one from SS and it works nicely. To make the VB one work, I will need to modify the plunger. I had used the plunger from the original rotted master cylinder because the VB one doesn't come with it already attached as the SS does. The plunger has a bulb shape at the end with about a 1/2" of rod that extends beyond the bulb part. That extension was pushing the piston partially in and not allowing the pressure to release from the MC. I will need to cut off that extension and smooth the bulb for it to sit properly. I guess the VB master cylinder will just sit on my garage shelf now.
 
M

mikephillips

Donation Time
On Sunbeams there were at least two different pushrods as the "dish" in the outer end of the piston got deeper from the IV to the V. To compensate the pushrod got a longer extension on the cylinder end to fit into the piston. Either pushrod will work as long as it matches the cylinder end. You have a later pushrod and the VB cylinder sound like it was the earlier design piston. So either requires an earlier pushrod or later piston to all work.
 
You must log in or register to reply here.
Top