Brakebooster not working or?

[Belgium R/T -68]

After finding a lot of faults on my brakesystem the "only" thing that seems to be left to fix is
the power assistance. I have installed a rebuild stock booster and mc but still no change.
The front discbrakekit is a MP-brakes singlepiston set-up, the distributionblock is a "new" stock
from Inline tube and the booster/mc is from "theramman". Could it be that these different parts doesn't match together or? Should I try the distrblock that came with the discbrakekit? How can
I exclude that my booster doesn't work?

Per

[elacruze]

Um, what were the symptoms again?

[The70RT]

If your booster isn't working It will be like putting on the brakes when the engine is off or when you apply the brakes the engine idles rough.

[Belgium R/T -68]

I have good enginevacuum but my breaks feels the same with or without engine running.
I can stop the car but that's all, wouldn't drive over 40 mph.

Per

[The70RT]

I have good enginevacuum but my breaks feels the same with or without engine running.
I can stop the car but that's all, wouldn't drive over 40 mph.

Per

Sounds like you got a dud to me then.

[Tilar]

   Are you checking the vacuum at the brake booster itself?

[Belgium R/T -68]

Yes, I checked it at the booster. What do you mean with dud?

Per

[Tilar]

"dud" means it is no good or doesn't do what it was designed to do. I think it came from WWII with bombs that didn't go off. They were referred to as a dud.

[doctor4766]

How many inches of vacuum do you actually have?
I believe you need around 18" to sucessfully use a booster.
Found that out when I inadvertantly installed a 509 lift cam and couldn't stop the car on it's first run. (MP cam was incorrectly packaged)

[elacruze]

I have good enginevacuum but my breaks feels the same with or without engine running.
I can stop the car but that's all, wouldn't drive over 40 mph.

Per

if it feels the same with and without the booster, then you've isolated it to the booster/master cylinder area.

I'd check the manifold vacuum with the booster attached and with it blocked off. If the vacuum is less with the booster on, it's leaking.
As said above, there is a minimum effective amount of vacuum for a booster, but I can't say what that is.
It's also possible that the booster is defective internally, and the valving is not allowing the vacuum to activate the assist.
I've never had a booster apart, so I don't know exactly what's is there, but I'll do a little research.

Looking at a few pictures

It could be as simple as your check valve is stuck, not allowing the booster to evacuate. Certainly the valve inside could be faulty. Verify that you have vacuum at the check valve. If you know somebody with a vacuum pump, you could attach that to see if you need more vacuum for that particular booster.
A last thought, it appears that the air that modulates the boost comes from the back of the booster, along the brake rod-are you certain this is not blocked off, or covered with plastic from shipping or something?

[doctor4766]

if it feels the same with and without the booster, then you've isolated it to the booster/master cylinder area.
I'd check the manifold vacuum with the booster attached and with it blocked off. If the vacuum is less with the booster on, it's leaking.
As said above, there is a minimum effective amount of vacuum for a booster, but I can't say what that is.
It's also possible that the booster is defective internally, and the valving is not allowing the vacuum to activate the assist.
I've never had a booster apart, so I don't know exactly what's is there, but I'll do a little research.
[/quote]

Also check that your headlight vacuum line isn't sucking air through a split or disconected hose and robbing you of the valuable vacuum.

We can only assume your braking system has worked in the past since you have had the car , otherwise, if you have fitted up new components to a non factory boosted or non running car there could be a number of other issues to look at...

[Belgium R/T -68]

The car is a discbrakecar from factory but now has aftermarket discbrakes front and drums rear.
Distributionblock is new "stocktype" and not the one that came with the discbrakekit.
The booster is a rebuild stocktype.

If you pump up the brakepedal to full pressure before starting the engine the pedal sinks a
little bit at start up which should indicate that the booster works?

Jacked the car up and the rear brakes doesn't take if you give throttle, on idle well.

12-14" at idle and up to 20" when giving some throttle, vacuum.

Suggestions welcome.

Per

[elacruze]

If you pump up the brakepedal to full pressure before starting the engine the pedal sinks a
little bit at start up which should indicate that the booster works?

12-14" at idle and up to 20" when giving some throttle, vacuum.

Suggestions welcome.

Per

What means 'pump up'? You should not have to press the pedal more than once to get pressure. 14" vacuum seems like marginal at best. What's your base timing? Have you played with idle timing to obtain best vacuum?

If your brakes are brand-new, the drums in particular are pretty weak until broken in, at least 500 miles for full effect.

[Belgium R/T -68]

I mean pumping like 2 times, pedal doesn't move far, then start the engine and pedal sacks a little bit.

Busy with tuning, 16° on idle and total about 32-33° at 2500.

When bleeding rear brakes, oil is coming out not much faster/heavier then at gravitybleeding.
Shouldn't it be pressurised oil coming out? Also after a couple of seconds with pedal pressed down
and bleederscrew open the oil starts to be sucked back.

I have removed the hold off valve to the rear brakes due to wrong fittings on the brakelines.

Per

[elacruze]

Something is definitely wrong, you should be able to shoot brake fluid everywhere like a fire hose, threatening your paint and your cat and panicking you.

[Belgium R/T -68]

Something is definitely wrong, you should be able to shoot brake fluid everywhere like a fire hose, threatening your paint and your cat and panicking you.

Was my thought aswell, can it be the rod that is playing with me?

Per

[b5blue]

In that diagram, see that nut on the end of the rod? That nut is adjusted to be just short of the master cylinders plunger. In the past if I adjusted it too long and it touched the plunger the brakes would not work well. When I had a 509 lift cam in the past, I needed a vacuum reserve can to hold more vacuum, but that was for repeated braking, it worked (once) OK but then quit boosting until it built up vacuum. That old set up with the 509 cam had a similar vacuum reading like you have now so I don't think that is the issue. When you force bleed the rears it should squirt out with a good strong stream of fluid. Residual pressure valve just keeps a small amount of pressure to hold the slave cylinder seals tight in the bore. I'm thinking a restriction somewhere in the system or your rod with the nut in your booster is too long. (or both)   

[Belgium R/T -68]

Will start with the rod and after that loosen connection after connection untill I get oil squirting
out. I guess eliminating faultsources one by one is my only option starting at the rear wheels.

Per

[b5blue]

Unbolt master cylinder, it should move enough out of the way to turn nut in so rod is shorter. Repeat till you can feel brake peddle linkage have just a tiny bit of space before engaging master cylinder when pressing on the brake peddle with your hand. (With the motor off and no vacuum in the booster) You will be able to feel it clearly and with practice get it down to a very small movement before it touches the master's plunger, then it is adjusted well. Be certain the front pads and rear shoes are adjusted just a hair from touching. Good Luck Per!   

[Belgium R/T -68]

Thanks Neal, I could use that.

When the car is jacked up in the front and I move the wheels from one side to another, the brakefluid goes back in to the reservoar everytime the front brakehoses moves due to me steering.
Is that normal?

Per

[b5blue]

No? 

[Belgium R/T -68]

When the car is jacked up in the rear it works like it should but not on the road. Also the pedal takes very deep before the car stops and it's not possible to lock the brakes on the road. in fact the pedal goes deeper down when engine is running (powereffect) then when not running.
Have gravitybleed all afternoon and no air in the system according to my opinion, rod also OK. What do I do next? Brakeshoes not close enough to drum?

Per

[elacruze]

Now we're getting somewhere. You can feel the booster having some effect.

One place that traps air that nobody thinks about is the brake line coils below the master cylinder. I've attached a photo showing the poor placement of my own, back when I didn't know about it myself. If there's a low spot, air can stay in it and not have enough fluid movement to chase it back to the master or to the wheels.

[b5blue]

YUP sounds like air, or you have installed the residual valve backwards. (?)  (Your bleeders are coming out the top in the back right?)   

[Belgium R/T -68]

YUP sounds like air, or you have installed the residual valve backwards. (?)  (Your bleeders are coming out the top in the back right?)   

Don't kick on a man already laying Neal. Actually the residual valve was mounted backwards due to wrong brakelines so it's now just a pass thru.

I will check for air in the "curly" area. Any idea why the oil is forced back up into the reservoar
when I'm turning the wheels?

Something else, how tight do you adjust the rear brakeshoes? They have to be adjusted with drum on I suppose, otherwise the drum wouldn't go on.

Per