Disc conversion problems...

#1
I installed a front disc/ rear drum conversion on my 63 impala. Along with the install I put in the booster mount on the firewall that raises it up. I adjusted the lever on the mount so it approx.1/4 inch away from the firewall, when the pedal is up. Pushing down on the pedal lets the lever max travel.Adjusted the pin on the front of the booster so their is free play. Adjusted the pin on the end of the booster so there is a very slight gap. Had to adjust the pin all the way in. I have bled the brakes six times..the rears are so so, the fronts are barely stopping. When the brakes are bled fluid comes out, no air The fluid level goes down in the master. The pedal is hard, never hits the floor. It is like the fluid is moving but with no force?
 

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1958 delivery

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#4
I installed a front disc/ rear drum conversion on my 63 impala. Along with the install I put in the booster mount on the firewall that raises it up. I adjusted the lever on the mount so it approx.1/4 inch away from the firewall, when the pedal is up. Pushing down on the pedal lets the lever max travel.Adjusted the pin on the front of the booster so their is free play. Adjusted the pin on the end of the booster so there is a very slight gap. Had to adjust the pin all the way in. I have bled the brakes six times..the rears are so so, the fronts are barely stopping. When the brakes are bled fluid comes out, no air The fluid level goes down in the master. The pedal is hard, never hits the floor. It is like the fluid is moving but with no force?

Please explain, how do you have two pins on booster:wacko.
You have a booster pin that push's master, it should have .030" gap, Rear booster rod to pedal should have no preload.
That firewall bracket requires the rear booster rod to be cut shorter to be able to assemble correctly.
 
#5
When I said two pins used the wrong terms. The rod in the end of the booster (firewall side), I adjusted so there is no free play. When I removed the booster and pressed on the pedal the pin extends about a inch. I adjusted the pin so there is a very slight gap between the pin and the master cylinder.
 
#6
Looks like when I fully depress the pedal the fluid moves but the force of it is not strong, so it does not operate the calipers and rear brakes with proper force..could the proportioning valve be limiting the pressure?
 
#8
I do not believe the lines are wrong..I used preformed lines and checked ok. I was also thinking the booster may not be doing it’s job. I have vacuum at the booster, but never checked exactly as I do not have one. Well a trip toHarbour Freight or the borrowing route.
 

1958 delivery

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Supporting Member 2
#11
Take master off, measure the travel of the front pin when pedal is fully pressed, then measure how far in the master plunger pushes in
The booster pin travel has to be at least the same, more is ok. Without actually measuring I'm guessing around 1" to 1.25"
If pressing pedal doesn't move booster pin as far then it will never fully engage master
 
#12
Hooked up a vacuum gauge..@ 800 rpm 13~14 in/ @ 2000 rpm 15 in. Not great, but should be enough. I removed the master cylinder and measured the travel of the pin that goes to activate the master..it was 1 1/8 inch...That seems good, again the pedal is not spongee, it is rather hard. Going to try pressure bleeding tomorrow and see how that goes..
 

1958 delivery

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Supporting Member 2
#13
So your complaint is the brakes aren't stopping as they should?
Do you have a high, firm pedal? If you can press the brake pedal and still are able to rotate a rotor due to calipers not grabbing much-you have air in system
If you put all brand new stuff you usually have to go through 4-6 qts fluid to get air out. best with a power bleeder. I use the harbor freight that you siphon at each wheel, hooks up to your air compressor.
 
#16
It is in the lower hole. Pressure bled the brakes today twice...sucked out 18oz with the pressure bleeder. Basically no change.. the back drums seem much better than the front discs. I did notice that with the master removed form the booster and the pedal is depressed it goes down further and the pin from the booster goes out a little further. How much does the puck in the master cylinder travel, now I am thinking maybe the master is defective,,it seems like the front line may not be able to deliver enough pressure...I am stumped...
 

La Hot Rods

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#17
To test the booster, you want to pump the pedal up several times and hold it without the engine running then start the engine, if the pedal goes down the booster is working if not then it is bad.
 
#18
I noticed another thing today..The rod that goes from the brake pedal to the lever in the bracket that raises the height of the booster was in the lower hole. Notes said that the lower hole was for pwr brakes, but using the height raising bracket I moved the rod to the upper hole making it level, per the bracket maker. Seems to help.
 
#20
Well still messing with the brake problem..Pressure bled a four brakes twice..not much better. I removed the booster and hooked the bleeder up to the vacuum line and would not hold a vacuum, bad check valve..retested and now holds a vacuum. I compared it with a friends Chevy, exactly the same. Now I have a noticeable difference with the engine running. Brakes ( front ) still not locking up strong with the brake depressed, Noticed a slight film of brake fluid on the brake booster, tried bleeding all the brakes 5 times..Going to try a new master cylinder.
 
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