elisowski

Is there a way to test the master cylinder for correct operation? There is a small amount of fluid leaking from where the power booster meets the master cylinder. I wiped it off before I bled the brakes today, and I notice it has returned. I had the master cylinder off once before when I removed the shock tower brace.

My pedal keeps going to the floor, but will pump up after 4 or 5 pumps (with the car turned off). Stays soft when car is idling. I have a vacuum canister that will hold about 20 lbs of vacuum.

I bled the brake lines today with a vacuum bleeder. I pulled 18 oz of fluid through the lines and then bled them again using the brake pedal method. I bled them in the proper sequence PR, DR, PF, DF. I do not have ABS.

Is there a procedure to check the master cylinder?
What would cause fluid to leak at the master cylinder/power booster interface?

shoebox

IMHO, if there is fluid coming out of the master cylinder, you don't need to do any testing, you need to replace it.

elisowski

I had the master cylinder pulled off of the power booster today. There is no fluid leaking from the rear of the master cylinder or anywhere else. The rear of the cylinder was dry. The fluid must have been there from it being filled before.

So , how do I know if the power booster or the master cylinder is the problem?

Also, since I do not have ABS on the front or 9" ford rear, would EBCM have anything to do with the soft pedal?

mdacton

does it still have the soft pedal?

what M/C are you using?

I had a problem with a strange and it would not get the air out of the line lock. I had to bleed it at the line lock and the regular, had other problems too. But strange helped get it figured out.


If its stock, I would just keep doing what you are, the M/C would be badif its bypassing.

a bad booster would make the pedal really hard, sometimes you may hear it leak vac. when you press the pedal.

elisowski

It only has a soft pedal when the car is running. Which makes sense with what you say about the pedal being hard to push if the booster is bad. It will firm up without any vacuum.

I can pump it up with the car off and keep my foot on the brake pedal and as soon as I turn the key the pedal just sinks.

I have a stock m/c.

I also have line-loc. I've bled the line lock each time I've bled the brakes. That's how I really noticed the problem because I started to roll out during the burnouts.

What else did strange have you do?

mdacton

I think you have air iun the front or a bad m/c


I have all manual, stange had me swap lines on the m/c to change bias b/c its a race car( I did not have enough rear brake) also checked the line pressure etc. But we are working on 2 different things.

elisowski

What is your line pressure?
Where did you check it? (ie, last hard line connector before the caliper, etc)
Where did you buy the gage?

This car is slowly evolving into a mostly race car, so I would not be opposed to a manual brake set-up. Are you happy with the conversion?

mdacton

I am happy with the conversion.

You can tap a port on the line lock to get the pressure. They sell brake gauges in summit or circle track shops etc.

A guy here sells a kit jakez28 also burkhart sell a nice conversion kit also. The feel of the pedal is alot better and its cleans up the fire wall.

elisowski

Did you replace your rubber lines with braided stainless steel lines?

I talked to a GM tech today and he said he thought that it sounded like the rubber hoses were stretching out and making the brakes feel soft.

What do you think?

I'll look for the conversion from Jakez28 or Burkhart.

mdacton

no I still got stock lines.

If its that bad it should be really obvious. I don't think thats it, it could be but probly not

elisowski

I'm going to Summit tomorrow to buy the guage.

I sent a PM to Jakez28 for the manual m/c.

I was browsing Summit's catalogue and looking at Disc brake upgrade kits. The Wilwoods 6-piston need manual m/c but they say you need 17" rims for clearance.

Strange has a set for 11" rotors but are steel and 4 piston.

I'm nervous about the clearance of my Weld Telstars w/skinnies.

Are you still running the stock front brakes or did you swap to a better disc brake set-up?

elisowski

I bought the gauge and the stainless lines. Had to wait a day to go back to Summit to get the right fittings to install the lines.

Installed the gauge today and was only seeing 200-300 psi on the line lock port. (should be 1200 psi according to the SSBC gauge instructions).

Guage kit did not have the proper fitting to put the gauge on the caliper bleeder (imagine that). So I had to rig a tee to attach it to the brake line itself.

The pedal is extremely hard to push (car running and off). Can only get a spike of 400-500 psi when I really push hard.

I'm thinking that it's the master cylinder leaking pressure internally.