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

[The70RT]

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

You can adjust the rear with them off because if you try to put the drum on and you can't, then your too tight. Adjust them for they just barley touch. You may have to adjust a bit after they seat in.

[elacruze]

I adjust brake shoes with wheels on and lugs tight, because it may distort the drum a tiny bit. Rotate the wheel, tighten the adjuster until you hear the shoe begin to touch the drum. Push the pedal to set the shoes, then readjust just until you can tell the shoes are beginning to drag the wheel-enough to just feel the difference when you rotate the tire by hand. This small amount of contact will polish off after only a few miles, without excessive heat.

The fluid returning to the master cylinder is normal, just the volume in the hoses changing slightly as they compress. This should be a very small amount, though, unless something else is going on like your calipers are being pushed back some while turning the wheels.

[b5blue]

I agree!

[The70RT]

I agree as well but it is easier for me to adjust the star adjuster with the drum off and back on a couple times. If you have new drums they come off and back on easily to get the same slight rub effect.

[Belgium R/T -68]

Couldn't a test be to adjust the shoes untill they are tight to the drums because if the pedal then still goes deep it must be air.

Something else, when driving backwards the brakes almost doesn't take at all.

Per

[b5blue]

You can snug them well but undoing can be a challenge! It should stop well in both directions, I wish I could help you Per! 

[Belgium R/T -68]

You can snug them well but undoing can be a challenge! It should stop well in both directions, I wish I could help you Per! 

I will send you a planeticket Neal, then you can see our new lemonbeaglepuppy.

Per

[Belgium R/T -68]

My residual valve or the "hold off valve", the brass valve located on the front to rear brakeline under
the front seat is empty. My brake lines front to rear had the wrong fittings and since in and out has 2
different sizes I removed the valve inside untill I have new brakelines or fittings so I could drive otherwise NO oil is getting to the rears.

Now something hit me, can it be that the now empty brassblock act as an airpocket and that's the reason I can't get the air out?

Untill I get new lines/fittings I could remove the brassblock and use a piece of hose instead to test if there will be any difference?

Per

[b5blue]

A: When can I leave! B: Can I have the pup!    We are on to the problem! Post pic. of what you have, my understanding is this, the distribution block for your set-up now should just be for splitting front brake line from master to left and right. The rear line needs a "proportioning valve" that is adjustable to restrict (reduce) line pressure to the drum brakes, that compensates for the difference between disk (That uses a much higher volume of brake fluid) and drum. (That have much smaller volume fluid needed.) The brass parts/blocks below your master cylinder did 2 or 3 things from the factory when new, 1: All had a "unbalance" detector (Tiny rod that if pushed forward or rearward from a large difference between front and rear brake pressure) that did 2 things, A: Acts as a switch since if it moves it (being held in place by tiny O rings thus insulated from being "grounded electrically") grounds out to the brass block and triggers the "Brake" light on the dash. B: (If I'm not mistaken) Acts as a limiter to restrict flow to the low (malfunctioning) side to give maximum fluid to the side (front or rear) that is working. BE CERTAIN IT IS CENTERED! (If all your electrical is 100% working and the wire is hooked up that, the dash brake light should be on if it is not centered) 2: Splits output from master cylinder for left and right front brakes no matter if disk or drum. (Rears are split for left and right at Tee Block on axle) 3: If the car had disk brakes there would be the "proportioning valve" feature located there. That feature (the factory "proportioning valve) is/was a very generalized part, the same one used for all cars, not "tuned" for each cars specific needs and best working ratio for engine weight, size brakes and such. The residual pressure function (Located inside the factory master cylinder) was intended for the old way they made drum brake slave cylinders, it held some pressure to the slave cylinders rubber seal to hold it tightly in place, preventing it from seeping brake fluid when under no pressure at all. (fully relaxed) It is my understanding that for many years now they have added a thin steel disk to that seal and the residual pressure valve is not needed, it could still be useful by retaining some pressure to effect a kind of "pre-load" in there to reduce reaction feel but if the slave cylinders have been replaced in the last 15-20 years not required. My car, a 10 inch drum (front and back) has just been converted to manual brakes. (Due to booster failure and a lack of money or desire to deal with booster issues like you and others have experienced) I like the results far more than expected, not having that "Z-bar" set-up altering peddle ratio (I drove the car for a month with no booster function     but with that entire assembly all still in there, booster vacuum plugged off) the difference is huge! The Z-bar assembly cripples peddle pressure and without boost took much force to slow the car even for me. (I'm not weak after 30 years working construction every day!) Well there is a review of what I know to tell you, I'm certain some if not all you knew but 2 heads are better than one. Please read the Mopar Action "Disk-O-Tech" online archive as right now you have all of the components they recommend using and it is the source of much of what I have mentioned. (Along with my own findings) You can use this as a guide to alter what you have to get it to function and adjust then you will know how to order replacement lines specified to your exact placement of modifications for a finished system.         

[Belgium R/T -68]

OK, here's what I have now and was sitting on the car from the beginning although these are new
aftermarket. As said, car is factory discbrake. The first pic shows the hold off valve that is now
turned 180° and emptied of the valveparts. There was my idea about that piece now creating airpockets. Second is the block that distributes from mastercylinder.

[Belgium R/T -68]

Here are some options. I have this valve that you can regulate the pressure from front to rear,
maybe that one instead of the hold off valve? Need some extra fittings though because you can't put the brakelinefittings directly into that valve.
Secondly, the distributionblock on pic 2 came with the discbrakekit but since I use stock mastercylinder I didn't think it would brig anything to use that one, don't like the looks of it.
What's best thing to do? Anybody with same factory set up have the same parts?

Per

[b5blue]

YES and Yes!

[Belgium R/T -68]

YES and Yes!

You mean use the valve with manual regulation?

I bought it 10 years ago but never used it so I guess it should be alright?

Per

[b5blue]

Correct, that is the right part to install. I have a "new" old school Mopar racing one it's big, heavy, and ugly and I will be using it for the same thing. Remember if you sort all this out with adapters you can specify the location and size of fittings on the new lines you get and then it will look nice. I do believe your booster is working, you did say it sucked down the peddle when you started the engine. (That's a good sign)    

[elacruze]

I think I missed something...

You have no holdoff valve? If not, the rear brake shoe springs will push the cylinder pistons all the way back and you'll get half a pedal or worse, maybe two or three pumps to get it to firm up. If there's any air in the system it's even worse.

[Belgium R/T -68]

I think I missed something...

You have no holdoff valve? If not, the rear brake shoe springs will push the cylinder pistons all the way back and you'll get half a pedal or worse, maybe two or three pumps to get it to firm up. If there's any air in the system it's even worse.

No, had to remove the valve inside the brassblock because in and out were mixed so I couldn't fit the brakelines correct. So, fix the holdoff valve
and/or mount the MP valve with regulator?

With drums off and pumping the brakepedal, the shoes doesn't moves.

Per

[elacruze]

I'm wondering if your master cylinder is missing some parts!

Try plugging the line ports off directly on the master cylinder, see if you get a tight pedal. Work your way downstream, opening one line at a time until you find the culprit. This is messy and requires the correct caps and plugs, but the scientific bulldozer will not be stopped.

[Belgium R/T -68]

OK, will do it again. Did it before I found out that the hold off valve was wrongly mounted and stopped the oil from going to the rear.

What about that valve now, is it necessary to have one? Does the adjustable one have the same function?

Per

[maxwellwedge]

Try properly bleeding the M/cylinder as well. An improperly bled master will cause those symptoms as well.

[b5blue]

I'm not following what elacruze is saying about a hold off?    The shoes rest against the large stud on the top of the backing plate and adjust on the bottom end, (with the adjuster) this all has nothing to do with a residual pressure valve's function.

[Belgium R/T -68]

I think I have been misinformed at the shop concerning the function of the hold off valve. When I read on different sites selling them the purpose
is to delay the rear brakes a split second and NOT keeping the oil from going back like I was informed so I think the valve was correct mounted.

Will look for correct fittings today to be able to install the MP valve, the adjustable. Since in and out are marked that hold off function should be there aswell?

[b5blue]

Have you read the "Disco-Tech" article yet?  (It covers how that valve is adjusted.) I'm thinking the confusion is terminology the valve would be acting as/like a "hold-off" as it is a restriction in the line, same thing, ether or in name. This thinking would make elacruse's comment make sense to me as we are not talking about "residual pressure" valve. (Perhaps it's just me!  )   

[Belgium R/T -68]

I hate brakes, I hate brakefluid, I have the taste of brakefluid in my mouth. My wife always complains that I stink from it and it sticks everywhere.

Per

[b5blue]

  Tastes better than blood Per!

[doctor4766]

And can't smell any worse than gear oil

[elacruze]

I'm not following what elacruze is saying about a hold off?   The shoes rest against the large stud on the top of the backing plate and adjust on the bottom end, (with the adjuster) this all has nothing to do with a residual pressure valve's function.

Terminology failure.
'Hold off valve' is Per's words. Technically it is a 'Residual pressure valve'. I used his term communicating with him.

"The struggle for definition is veritably the struggle for life itself."
--Thomas Szasz

A 'residual pressure valve' prevents fluid from returning to the master cylinder from the brake cylinder(s) _below a specified pressure._ The brake shoes do indeed rest on the top stud while assembling, but not after the system is adjusted, bled, and put into service. The cylinder pistons move the shoes off the stud as far as necessary to press them against the drum, then the residual pressure valve holds them out there against the effort of the return springs. From Wilwood; (Summit racing)
http://www.summitracing.com/parts/WIL-260-1876/
Ideal for drag racing, Street Rods, and many off-road applications, these inline residual pressure valves from Wilwood retain a minimum brake line pressure to help eliminate excessive pedal travel. These 2 lb. valves are used in disc brake applications where the master cylinder is mounted below the horizontal plane of the calipers, and fluid drainback occurs, causing excessive brake drag. With drum brakes, 10 lb. valves are used to compensate for return spring tension in the drums. They're made from billet aluminum and are color-coded for easy identification."

This, and possibly air as well, sound like part and parcel of Per's problem.

If the brakes are not adjusted close to begin with, and the master cylinder doesn't have enough volume to push hard against the drum before it runs out of stroke, you get no brakes in the rear.

[Belgium R/T -68]

Where do you mount those ones? One for each side?

Per