57 Chevy has no brakes!

[kb426]

If you can borrow a pressure bleeder, that could be the quickest way to see if you have another problem. I use a miteyvac also but I don't feel that it is as good as the pressure bleeder. Good luck!

[ron morrow]

A bunch of yrs ago I came up with a one person bleeder. I took a i qt glass mayo jar with a metal lid (washed it first) drilled two 3/16 holes in the lid. Raising a child with asthma I had 100' left over nebulizer hoses. I put one 8' hose into the lid, extending just enough to seal. I attached a few hoses together to reach the farthest away wheel cylinder and made sure it reached the bottom of the jar. I would loosten the bleeder nut on whichever wheel I was bleeding, slide the hose over said bleeder nut. Start the car, pop the top off the master cylinder and make sure it's full. Disconnect the vacume advance hose off the carb base and attach the short hose. Stand close by and repeatedly refill the master cylinder till the jar was either full or I thought it was completely flushed, at which time I'd go tighten the bleeder nut, reattach the vacume advance hose and Walla!  Flushed and bled in just a couple minutes. It can be moved to any wheel of your choice, empty the jar and start all over.

[wayne petty]

Hello;
been working on this now for this afternoon. Got the new master on, brakes bleed, rear shoes adjusted. When the car is not running, (booster not working) the pedal seems good but a slight bit spongy! When I start the car (booster working) the pedal goes down to the floor with no effort!
What the heck is going on? Could I have a bad booster too?
Someone please give me some pointers!

Bruce

brand new pads and shoes... before you break them in by driving the car a few blocks may have a soft pedal... the surface of the pads and shoes is not pressed flat and worn smooth that happens in the first few applications of the brakes...

oh... and the best 20 bucks i ever spent was for this brass bodied brake pressure bleeder..

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92474

i have changed out the standard hose for some silicone vacuum hose i got off a saab turbo car.   this unit also if you look carefully when you have it in your hand.. can be unscrewed to clean the internals..

most parts stores also sell the same thing.. but they get 40 bucks for it..

Q:     did you turn the surface of the drums and rotors?   are they smooth or is there a small ridge at the edge ?

Theory)  if there is a ridge at the edge of the rotor or drum.. there has been wear..  rotors wear faster at the outer edge than closer to the middle..      brake drums wear also.. but when they wear... they also take on a bell shape... slightly..    both of these wear patterns cause brand new shoes and pads to only contact the braking surface.. this will cause a spongy pedal..    

i will ask .. if your pedal is up... and still spongy.. but it does not go to the floor...  take a few block drive.. if its safe to do so...    then come back and check the adjustment on the rear shoes..  you can do that with a screw driver by going through the adjustment slot.. pushing the star wheel forward .. then levering it toward the back.. see how far it moves..  got more than 1/8" of movement .. you might want to tighten them up till you get it down to about 1/16"  its kinda up to you.. as the self adjusters will usually take up the slack after you back up a few times...

i am also taking it that there is no play in the rear axle bearings... up and down play..??   that will cause all kinds of weird braking problems.. as the drums are not centered do to the offset..  when the brake pedal is depressed.. it has to center the brake drum by lifting the car a fraction of an inch before the brakes can get tight...


you can test the booster for proper operation...
warm up the motor.. so its easy to start..
motor off.. pump the brakes 3 or 4 times... till you are sure there is no vacuum left..    with your foot lightly on the brakes.. start the motor.. see if the pedal pulls down or drops slightly.. almost instantly..  this indicates the booster is getting proper vacuum..

take your foot off the brake pedal...   let the engine run for 20 seconds more...     shut the engine off...     push the brake pedal 3 more times.. it should be higher each time as the vacuum is used up...

if the pedal does not get higher as the vacuum is used up.. sometimes you only get one full and one partial assist..    

this instant loss of boost when you shut the motor off... indicates a bad booster.. if it passes the previous test..

if your pedal stays hard... on both tests... i would look for a vacuum restriction.. or a totally blown booster...

~~~~~~~~~~~~~~~~~~~~~

one thing i have found lately.. the plastic bleeder hose adaptors that screw in.. need to be tightened with a wrench  to prevent air leaks.. i take it that the plastic is too hard..

with the brake bleeder .. i have found that not loosening the screw very much is better... loosen it more than a turn and it leaks more air around the threads...

and for the last thing... i have found .. that just barely cracking one bleeder screw at a time...  and with your hand.. rapidly patting the brake pedal....

you can build up line pressure but since you are not passing the fill port in the master.. there is no fluid being pulled back... this squirts fluid out at the wheel... and works really well..  after some practice... since i work alone.. and most of the time.. my brass bleeder pump is buried in the tool pile .. its just faster...

there are also speed bleeder screws available..  these have a check ball and a spring.. loosen them slightly..  and you can pump the pedal to speed bleed the brakes...

i really love what they use in professional racing classes... a pair of check valves and 2 hoses to each caliper..   this keeps the fluid circulating.. in the bottom hose out the upper hose... it properly done.. the bubbles will come out in the master cylinder...  

i hope that this has helped..

[BFS57]

Hello;
Just to bring us up to date on this! I finally took my car to a shop (claiming to be a hot rod shop). They put a power bleeder on and bleed the snot out of the system.
At that point, I had pedal (very low) next the shop adjusted the rear brakes and adjusted the distance between the booster and master. I paid my bill and drove it around the corner (thank god) to my work. When I arrived, the rear passenger side wheel was SMOKING!!, I jacked up the car and loostened the adjuster on that wheel as I couldn't turn the wheel by hand (in neutral) and did the same on the other wheel.
I drove the car home that evening, good thing it isn't too far (10 miles) I begin noticing the motor working harder and the car not free coasting like usual. Had the smell of brake burn going on! I knew that the booster rod was pressing on the master causing brake drag! I drove it back the to my work the following morning. That next morning I had good pedal when I stated out but soon the pedal was way up at the top! and the brakes were dragging. When I got to work I felt the wheels and they were warm, not blazing hot, but warm, the engine was working harder to make the car go.
When I got to work, I pulled the master top off and the fluid was at the brim! (I thought those guys knew what they were doing!) So, I used a paper towl to wick the fluid down to around 3/8".
Next I took the master loose to adjust the booster rod back down. To my suprise the adjuster in the booster was out about 3/16" so I adjusted it back down to about 1/16". Got in and didn't have good pedal at all!!
One question I have is I know they make a tool to find the exact measurement between the booster and master but I have only seen it at CPP (Classic Performance Products) What do you guys use to get this measurement???
I am going to my work today to try to get this thing working right! Meanwhile, I am noticing a leak at the front line going into the master so I am pretty much resolved to put a new fitting in there because the old one was not too good and I thought I could get away with that but once again, can't fudge this stuff!! (Why did the shop say I had no leaks?/)

Bruce

[enjenjo]

I made my own tool, it's similar to the CPP tool.

[BFS57]

I made my own tool, it's similar to the CPP tool.

Hello;
Don't tell me about it, give me more info, unless it is some sort of secret society thing I know nothing about.

Bruce

[enjenjo]

A link to a post I  made about it.

http://www.roddingroundtable.com/forums/viewtopic.php?t=2609&highlight=brake+booster+tool

[BFS57]

Hello;
I'm back! Still can't get this thing to work right! Got my second master, an aluminum copy of the cast iron corvette style with 1" bore ect. Got it mounted, power bled, and have been "FIGHTING" FOR PEDAL EVER SINCE!
When the brakes don't "drag" the pedal is low but works but I doubt if I could "lock em up" if I had to! When I adjust the pedal travel or booster rod till I have Good pedal, It seems though the brakes want to drag!
Am I overlooking something? I adjusted the rear drum brakes as far as I can go. Of course the rear cylinders and the master all are made off shore so I have my doubts!
Anyone had this problem?

Bruce

[enjenjo]

I want you to try something for me. with the pushrod adjusted right, which you say gives a soft pedal, clamp the front brake hoses shut, and see what happens to the pedal then. Don't drive it this way, for testing purposes only.

[Mikej]

Was the other master cyl. an inch also? If you give it a quick pump do you have more peddle.

[38HAULR]

With the mc/booster rod
What I do is , with the m/c pison in it,s rested state against the rear circlip ,take a measurement from the m/c bolt mounting face to the activating rod seat of the m/c piston.
I then,at the booster, measure the distance from the tip of the activating rod to the m/c face of the booster.
If the rod is too long you will get blocked compensating ports in the m/c, evidence of this is lack of steady drip at the wheel bleeders once open,other symptom is hard pedal and locking brakes.
Rod too short gives excessive pedal travel.
Frank.

[BFS57]

Hello;
Enjenjo, What am I looking for while clamping my front brake hoses off? I found a pair of "insulated" clamps that will do the trick, I just want to understand just what it is I am looking at when doing this?
Question; I know that most power brake conversions use a "combination" valve. I have the front lines from the master going to the front disc and the rear out of the master going to an adjustable proportioning valve.
What is the difference in the two different ways to plumb this system for disc/drum?
You know, If I keep this up, I will be a brake EXPERT!! (or at least know way more than the guys I took my car to)

Bruce

[Bruce Dorsi]

Unless I missed something, there is no mention of a residual pressure valve (RPV) in the rear drum brake circuit.

Depending on the year of the 'Vette master cylinder, I'm assuming it is for 4-wheel disc brakes, so there would be no RPV built into the master.

Drum brakes require an RVP.  .....Without one, a lot of pedal travel gets used to bring the brake shoes out to contact the drums.

[Bruce Dorsi]

Another thought:

Since you are not using a combination valve, you may want to consider adding a "metering" (aka "hold-off") valve into the front brake circuit.

The metering valve is often a component of the combo valve, but they are available as a stand-alone valve.  .....ECI is one supplier.

The metering valve delays application of the front disc brakes until the rear brakes have enough fluid pressure to overcome the shoe return springs and allow the shoes to contact the drums.

If you have a firm pedal but feel the rear brakes are not as good as they should be, your brake shoes may not be fully contacting the drums.  

Years ago, it was common practice to "arc" the linings to match the radius of the drums.  ......This practice has just about disappeared, but if your drums were refaced (cut) or if new shoes have been installed, there may be a mismatch of the arc, and only a small portion of the brake linings are contacting the drums.

[enjenjo]

Enjenjo, What am I looking for while clamping my front brake hoses off?

I'm trying to isolate the problem to find out where to look. What we are looking for is a change in the pedal feel.