Whibty | No Pedal Pressure | Brakes Have Been Bled | Video Included

All,
I've bled all brakes, no air bubbles coming out...no leaks...even went out and bought the motive power bleeder. The pedal is still soft and goes to the floor.


1) Photo -- I upgraded barb fitting into the master cylinder... from http://www.lsbilletworks.com/ per Norm B

2) First video -- no air coming out...all fluid and its the same way all the way around

3) Second video -- I can push the brake pedal all the way to the floor with my hand.

https://www.mattmaresch.com/Private-...ster-Cylinder/

It is possible you installed the callipers on the wrong sides and ended up with the bleeder at the bottom versus the top?

Norm

Did you adjust the push rod coming out of the brake booster so that it just allows the master cylinder piston to fully retract when the pedal is released?

Norm

Quote:

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Originally Posted by Norm B

Did you adjust the push rod coming out of the brake booster so that it just allows the master cylinder piston to fully retract when the pedal is released?

Norm

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Spoke with Whitby, we removed one of the spacers (had two installed) and sent him photos of the Power Booster Pushrod, attached below, I'm pretty sure it can't get any shorter...

Power Brake Booster - Pedal not pushed in:
Attachment 147007

Power Brake Booster - Pedal pushed in:
Attachment 147008

Removed Spacer...pedal still goes to the floor...its sounding like I've got a bad master cylinder?

Thanks.

You shouldn't be guessing about that pushrod to MC piston setting. There are specific ways to measure it and even tools made for that purpose. There is supposed to be .020” of slack when together. More than that and your pedal will move too much before engaging. Less and the MC piston may not be allowed all the way back against the stop. Lots of videos. This one is short and concise: https://www.youtube.com/watch?v=llA9...el=ZipCorvette. May not be the source of your problem. But is something that needs to be correct for your brakes to work properly.

I think we may have found your problem. Edwardb is correct, if the pushrod is too short or long your brakes won't work properly. I just checked my setup and I have no spacers at all. It looks to me that your pushrod is setup way too short. I set mine up on the bench before installing it in the car. It will be a little more difficult to do in the car and you will probably have to remove all brake lines so there is no other resistance to the master cylinder moving.
This is the procedure I used.
First I used the old pushrod I had from my manual brake setup to get a measurement of how far the pushrod extends into the master cylinder piston past the master cylinder mounting flange. If you don't have a spare pushrod you can file the end of a bolt to match the booster pushrod.
It doesn't have to be perfect, just close enough that you don't spend all day trying to adjust things.
Next I adjusted the booster pushrod just a little longer than the measurement I got with the previous step.
I then put the master cylinder on the booster studs and slowly pushed it in until I felt the pushrod start to move the piston.
Using the distance between the booster and master cylinder flange as a guide, I adjusted the pushrod shorter in small increments until it was just bottoming out in the piston as the master cylinder fully seated on the booster.
Now comes the tricky part. As Edwardb stated, the pushrod needs to be the .020" shorter than this. I used the TLAR (That Looks About Right) method. Using my .020 feeler gauge as a reference, I adjusted the pushrod shorter. If I remember correctly, it was about 1/4 turn of the adjuster.
Brakes work perfectly so I must have been close:rolleyes:

HTH
Norm

I've been following this intently, my pedal also goes to the wall... not fully bled though.

I found the part that Paul referred to, pricey little bugger for what seems to be a simple measurement - I'll need to check this out!

Master Power Brakes AC2003 Booster Pin Adjustment Gauge

edit found a cheaper on,much more tolerable for a one-and-done measurement
Sunyat Power Brake Booster Pushrod Pin Adjustment Tool (Blue)

found this in the Whitby directions:

Step 3
Screw end of booster push rod all the way in, as short as possible, use vise grips and a wrench for this.

Use one of the master cylinder spacers that came with your FFR kit between the booster and the master cylinder. If not available you may use ¼” spacers or a washer stack equal to a ¼” to space out the master cylinder. Seal the open area between the master cylinder and booster to keep it clean.


there's nothing about adjusting the length of the pushrod... must be 'common knowledge' for those who setup booster brakes more than once :)

another way to measure without the tool, well with a different tool that you may already have :)

https://www.youtube.com/watch?v=rYYzPIGoxfY

ok - checked mine tonight - used the 'tool' and realized that with only 1 spacer my pushrod was way too far forward, added a 2nd spacer and it's darn near perfect!

my pedal still goes to the wall, but I need to bleed the brakes fully to get some static pressure in there. Hoping that will fix things, otherwise - hmm....

after measuring into the master, I held next to the booster - as you can see the pushrod was a good 1/4" past the depth so it would always ride the brakes
https://lh3.googleusercontent.com/yO...-no?authuser=0

added a 2nd spacer, and it was perfect - almost touching but there's a very small gap
https://lh3.googleusercontent.com/st...-no?authuser=0

pedal still hits the front wall...
https://lh3.googleusercontent.com/db...-no?authuser=0

We tried one spacer, two spacer, adjusted the pushrod. Whitby believes the pushrod should be all the way tight and one spacer... He reviewed all the videos and pictures. He thinks it just may be a bad master cylinder.

Waiting for it to show up... I keep everyone updated on the progress...

Quote:

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Originally Posted by Padawan

We tried one spacer, two spacer, adjusted the pushrod. Whitby believes the pushrod should be all the way tight and one spacer... He reviewed all the videos and pictures. He thinks it just may be a bad master cylinder.

Waiting for it to show up... I keep everyone updated on the progress...

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pretty crazy if two of them are bad... will be bleeding brakes this weekend to see if that helps

Bled the brakes tonight took a whole quart for front and rear

one seeping leak at the master feed from the front line
the ABN bleed kit worked pretty well, I have a small 3hp compressor so it had to cycle a bit https://amzn.to/3vz4CQR
Attachment 147138

the pedal is firmer, but will still go to the floor with my hand - so my leg will surely compress it
sounds like I need to call Whitby ��

Most master cyl pistons have a check valve. I have read where too much pressure from the wrong direction and spring the reed type seal. I see you have used a compressor for your bleeding process. Could possibly be the problem.
I have had old master cyl get debris, probably not your case, under the check valve. Stabbing the brakes will give you a pedal, but is not a fix, just something to get you stopped.
I am not going to say you do not need a pressure bleeder, but with my complete Wilwood system, I just opened the bleeders and after a few minutes the calipers were flowing brake fluid. I did a few pressure bleeds with the pedal and never looked back. If you are not running abs, residual valves or proportioning valve, gravity bleeding should work. Good luck,

Quote:

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Originally Posted by Railroad

Most master cyl pistons have a check valve. I have read where too much pressure from the wrong direction and spring the reed type seal. I see you have used a compressor for your bleeding process. Could possibly be the problem.
I have had old master cyl get debris, probably not your case, under the check valve. Stabbing the brakes will give you a pedal, but is not a fix, just something to get you stopped.
I am not going to say you do not need a pressure bleeder, but with my complete Wilwood system, I just opened the bleeders and after a few minutes the calipers were flowing brake fluid. I did a few pressure bleeds with the pedal and never looked back. If you are not running abs, residual valves or proportioning valve, gravity bleeding should work. Good luck,

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yeah, with the ABS setup a gravity feed wasn't going to work... checked the pedal again this morning, firmer - but will still travel to the footbox wall... assuming it should 'stop', but is it via pressure stop, or physical stop in the brake setup?