67 dual master cylinder woes....

I'll try to keep this concise as I can. My brake system is all new except for the lines: Upgraded to front discs, new wheel cylinders and hardware in the rear. The brake system worked with minimal fade while at a stop light. I just rebuilt the front end and while I was at it I put a rebuild kit in the master cylinder. When I rebuilt it I noticed the residual valves were pulled out. I put a new one in the rear port and used an external 2lb on the front for the discs.
Bled everything out, brakes worked fine, put about 300 miles on.

One morning I went to drive it and noticed the pedal was soft, but working. The next day it was a little softer again to the point where I had to double pump to get a good stop. A few days later (no driving in-between) the pedal went right to the floor. With 7-8 pumps I can get it to brake. In all cases, if the pedal held it did not fade.

Puzzled, I adjusted the rear brakes and bled the lines, I even checked the self adjusters to be sure they are working right. Everything looks fine. No leaks anywhere. I pulled the master cylinder and disassembled it, nothing looked suspicious. No debris, no torn rubber.

Puzzled. Ideas?

It's a common problem on the 67 master cylinder. The bore is prone to heavy pitting. The way to solve it is to have it sleeved. White Post Restorations can sleeve it for you.

Duane in Tennessee

Donivan - The free play adjustment is setup correctly as the piston is at the rest position when the pedal is up. The pedal goes right to the floor unless you give it 7 good, quick pumps then it will actuate and hold with no fade.

Duane - I was thinking on that same path however I am having trouble reasoning why it would work better than before (no more fading at a stop) for 300 miles then go down so quickly. I would think the pitting issue would be a gradual failure. I did do a light hone on the cylinder before putting the new piston in. Perhaps the new rubber was too good and wore away any thing that was keeping it sealed?

sounds like maybe a wonky seal diaphragm in the master...

White Post - $175 for a rebuild/sleeve! and they might think about giving me a $20 credit towards my $40 rebuild kit.

I just had my MC done by white post,,,
I swear they gave me a new one!
Jim in NJ aka Casimier

White Post does a nice job,complete with a new finish on it.

Thanks for all of the input. I sent it off this morning, I'll update when I get it back. Price seems a bit higher than the guy in CA who just retired but no choice at this point.

It has been a frustrating series of issues to iron out over the past year. Hope to drive it for a bit after this.

How much do they charge to resleve??

See ^^

It doesn't take much pitting to loose the seal. It may look and feel ok but it just won't hold. I've also been told the dual MC can be a bear to bleed correctly. Possibly been an air pocket in it?

I too am sad Joe retired. I have a pile of MCs I was planning to send to him.

Duane in Tennessee

I'm sure the work is good but White Post has some of the worst customer service. I'll be using someone else if I ever have to do this again.

You guys know Vic in Calif. can hook you up on the 67 dual too, right? I ve seen White Post work and it's excellent, can't speak for the cuts. service though. You will be very pleased with what you receive back from them.

Thats a good point, I forgot Vic was set up for that. I would much rather spend my money with another vanner.

As far as White Post, if an owner of a business tells me I'm wasting his time I'm not too keen on being their customer. They also admitted they buy rebuild kits for these for less than $2 which makes me think they are charging a lot for the service. Maybe they make enough money from Jay Leno and don't need to worry about it.

Follow up...

I got the MC back and immediately noticed a shotty paint job on the lid. I inspected under the boot and found they bent the retainer clip. To top it off they delayed my shipment and did not send me back the parts I asked them to. I know some of you swear by them but White Post gets a big thumbs down after this experience.

I fixed the clip, bled the master, and got everything installed. Bled the rears first and we noticed the same issue. I would think being a dual it should have instant pedal even without the fronts bled. We had to pump multiple times to get pressure but again would not fade but if it was left alone for a minute the pedal would go to the floor.

Bled the fronts and it wasn't until I got all of the "foggy" fluid out of the last line that the pedal was good. I had some older brake fluid (just been sitting on the shelf half empty) I used on the last bleed that was a little opaque. I wonder if this had something to do with the issue? I would think since it is just air that it would be spongy, not loss of pedal.

In the end the brakes are better than they ever were. I still have an issue with the front pads glazing up though and I get a high pitched squeal while cruising. This has been chronic since I installed them. Should I try a different pad material?