Recentering shuttle in brake distribution block

[Ted Z.]

Dear friends: Let me start by thanking those who advised me through installation of new distribution block. It took two attemps but the newest is now in place and not leaking. Well, sadly, the job is still not done.
I attempted to gravity bleed the system but ony the fronts are dripping (quite significantly). The rears are not dripping. I gave a little pedal to stimulate but still inactive. (The rears bled very well before new block.)
My previous research tells me the shuttle in the d-block may need to be recentered.
Can someone please advise me on the steps to recentering. As you know, the block is solid and there is no way of centering the shuttle externally.
NOTE: until the shuttle is centered, I cannot bleed brakes. Most forums say power bleed, the vendor said not to power bleed. ???
Vendor said open caliper bleeders on the side that's bleeding. This creates the fault which triggers the shuttle to recenter while pedal is being depressed.
I would welcome specifics like pedal pressure; do I hear a clicking noise; how many trys does it take; do I open only one front bleeder, or both fronts; do I retighten bleeder valves before brake pedal is released? etc. Thanks in advance. Ted Zywicki (64289)

[Tom E.]

[Owen L.]

Re: Recentering shuttle in brake distribution block

I've no experience re-centering the shuttle, but have read that several really hard jabs of the brake pedal will do it. I believe it's addressed in the chassis or service manuals.

[Jeffrey S.]

Re: Recentering shuttle in brake distribution block

The shuttle will absolutely come off center when bleeding the brakes. In fact, the service manual indicates that the way to test the switch, after establishing that the electrical system is in good order, is to open a bleeder and have an assistant press the brake pedal. If the warning light lights, the switch is good. After closing the bleeder and depressing the pedal the shuttle should recenter itself. If the shuttle is stuck, opening one side of the system at a time (front and rear) and pressing the pedal could unstick it.
Jeff

[Tom E.]

[Ted Z.]

Re: Recentering shuttle in brake distribution block

For sure Tom. I think the confusion lies in the fact that the block is not a proportioning valve. But, I'll take all the feedback I can get and then sort. My take is I open the bleeders on the side that does gravity bleed ( front); depress pedal; (this shifts shuttle back to center as it detects a leak) then open rear bleeders that werent getting b-fluid and hope they bleed. Can you correct or add anything to this thinking? Thank you.

[Ted Z.]

Re: Recentering shuttle in brake distribution block

Good news/ bad news. I used some of Jeff's tips and shuttle must be centered. Brakes are now effetively gravity bleeding at all 4 wheels; right rear is slowest.. with gradsons help I I buddy bled all valves and craked MC ports under pressure to make sure good pressure. i now have about 1.5 inches of pedal. I started car (currently on blocks),put in gear and rears are grabbing. First positive sign in months.
Rear brakes a little clunky when i depress pedal. is this normal?
Some how I dont feel pedal is high enough even though this is a PB car.

[Owen L.]

Re: Recentering shuttle in brake distribution block

Are you supporting the rear under the trailing arms so they're not hanging? (Too much angle can cause binding of the u-joints.) Otherwise, a clunking from the brakes is not normal. Are the calipers secure on the arms and are the pads sized correctly such that there's only 1/8"-1/4" of forward/rearward space between the caliper housing and the metal backing plate? Make sure you have a couple-three lug nuts on the disk if the factory rivets have been drilled out.

As far as pedal height, I believe it's adjustable from under the dash. The AIM or service manual will probably have the procedure.

I've found that the brakes require a couple of bleeding sessions with road trips in between to vibrate any bubbles to the tops of the calipers. Pressure bleeding probably also helps force out bubbles.

Did you bleed the master cylinder if it has ever run dry?

[Ted Z.]

Re: Recentering shuttle in brake distribution block

Owen, (my granson's name)
So, I do not have anything supporting trailing arms. I have equal support on both sides of car using cement blocks under frame only.
I HAVE BENCH BLED MC twice. Last night I had Grandson depress pedal and I cracked open MC ports both front and rear barrels. They were bubbly. car guy told me to do this a few times until fluid is clear/no bubbles.
Im getting the feeling the worst is over. Ill take you up on driving and bleeding again. Are you talking about bleeding MC at ports after driving , or, bleeding all 4 corners? For me that would mean gravity bleeding. thanks.
PS: regarding calper install, I used correct length bolts and tightened to torque specs.

[Owen L.]

Re: Recentering shuttle in brake distribution block

Before you power the rear wheels again, move your blocks under the trailing arms so the rear suspension is aligned as if the car was sitting on its tires. The clunking you hear could well be the misalignment that happens when the half-shaft u-joints are binding due to misalignment.

When I said bleed, drive, bleed, I was referring to the calipers only. The master shouldn't require it.

Pressure bleeding can be relatively inexpensive using the Motive tools - or even less so if you have a compressor and can make your own master cylinder cap with a pneumatic hose fitting. (You can even mimic the Motive with a garden sprayer pressure pot.) This makes bleeding a one-person job and more time is spent jacking and removing wheels than the bleeding process itself!

[Ted Z.]

Re: Recentering shuttle in brake distribution block

Thank you. I also recall you mentioning I should lug down the after market rotars. I did not do that the first time I powered the rear wheels.
Since Im not much of a tool maker, I anticpate I will eventually get a power bleed. Do you like the vacuum method?

[John D.]

Re: Recentering shuttle in brake distribution block

Pressure bleeding can be relatively inexpensive using the Motive tools - or even less so if you have a compressor and can make your own master cylinder cap with a pneumatic hose fitting. (You can even mimic the Motive with a garden sprayer pressure pot.) This makes bleeding a one-person job and more time is spent jacking and removing wheels than the bleeding process itself!

Yes this is what ultimately solved this for me. I used a flat plate with a threaded air nipple hole and and clamped it to the MC with a c-clamp.

[Owen L.]

Re: Recentering shuttle in brake distribution block

Thank you. I also recall you mentioning I should lug down the after market rotars. I did not do that the first time I powered the rear wheels.
Since Im not much of a tool maker, I anticpate I will eventually get a power bleed. Do you like the vacuum method?

The only reason to snug the lugs on the rotor is to eliminate any loose parts that could cause the noise you heard.

I've tried vacuum bleeding but had a bear of a time knowing if the bubbles were coming from the caliper and lines or leaking in around the bleeder screw threads. I've read that there is a gray (?) teflon thread tape that may work to seal the threads so that the vacuum method works without that potential leak area.

If you do buy a Motive type pressure bleeder, a lot of folks say to throw away the chains that secure the lid to the master cylinder and use screw clamps instead – a lot less hassle and more secure. Same as John D. mentioned above. I use this method with my homemade lid and it's fine.

[Ted Z.]

Re: Recentering shuttle in brake distribution block

a big thanks for confirming a pressure bleed John Daly.

[Terry M.]

Re: Recentering shuttle in brake distribution block

Banging on the calipers with a dead blow hammer can get the air bubbles off of the caliper walls. I recommend it.