New brake system - no pressure...

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J

JF900

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I'm looking for some insight here...
I just replaced my whole system. I went with a standard Cardone master, early 70s factory disc / drum distribution and proportioning block, and no name roll control. After chasing a bunch of leaks around I have everything tight, but the system will not pump up more than just off of the floor and bleeds down in a few minutes. I bench bled the master cylinder before install and once after in the car. I pulled the master and inspected the seals and they look fine. Can this be a junk master or am I missing something? I'm contemplating just buying one of Dr Diff upgrade masters with two bolt adapter.
Any thoughts?
 
It took me a good while to thoroughly bleed the system to get a consistently firm pedal. Replumbed the whole front disc - rear drum system, 15/16 mc, adjustable prop valve.
 
The pressure comes from the master cylinder. I would make SURE the pushrod is depressing the piston in the master cylinder completely. I've seen master cylinders with the correct part number have a different offset at the rear where the pushrod installs that does not allow for full depression of the piston. Easily checked.
 
I'm pushing fluid while I'm bleeding so I'd think I'm stroking the master far enough?
 
Divenut said:
It took me a good while to thoroughly bleed the system to get a consistently firm pedal. Replumbed the whole front disc - rear drum system, 15/16 mc, adjustable prop valve.
Click to expand...
As a side question - how do you like the 15/16 master?
 
i had to bleed mine at the T junction on the axle
i also found that bleeding it then leaving it for a day or two then bleeding it got there eventually. the air migrates out with the changing temperature

other options pump the fluid in using a bit of threadred brass pipe instead of the bleed adapter like they do on motor cycles. you can do this with a diff oil bottle with a top of cap pipe. just hang it up upside down in the roof higher than the master. pipe from bottle to a sheel cylinder or caliper and the weight of the fluid moves into the system.
do each corner
or suck it through with a mitivac. again works better with a threaded pipe and plumbers tape than the bleeder,but doesn't necesarily move air caught in the upper corner of the calipers

All it takes is 1 small inch long bubble stuck somewhere in a pipe to give no peddle

as mentioned its worth adjusting rear brakes to locked on.. adjust back off again when done

Dave
 
RustyRatRod said:
"I think". Yeah, that's real concrete. Carry on.
Click to expand...
Let me rephrase that - it's starts pushing fluid from first 1/4" of pedal contact clean to the floor, so if it's not stroking the full length of the cylinder I need to change the ratio of the rod attachment and I'm not doing that.
 
JF900 said:
Let me rephrase that - it's starts pushing fluid from first 1/4" of pedal contact clean to the floor, so if it's not stroking the full length of the cylinder I need to change the ratio of the rod attachment and I'm not doing that.
Click to expand...
Some of the pushrods are adjustable, and if not, you can get an adjustable one. What I was getting at though is you may have an incorrect master cylinder. Being hard headed gets you nowhere with diagnosis.

One last thing and I'm done. Is the master cylinder level o the firewall? A lot of these mount so the front of the master cylinder points up. If that's the case, you will never get a pedal because it traps air at the tip of the master cylinder. You need to level it out to bleed it correctly.
 
A friend had a similar problem, Found out he had the front calipers on wrong right and left causing the bleed valve not to be completely at the top causing air pocket.
 
RRR - I'll check the attitude of the master. I know it's supposed to be parallel by it's design but the car is on stands and may be biased nose up. Not being hard headed about stroke but if it pushes fluid from beginning of pedal contact and goes to the floor an adjustable actuator pin does help and that's why I eliminated that early on.
Rick - Funny you mentioned that. I do have the calipers switched because when you convert a drum car to disc with early 70's single pot calipers you have to if you run a sway bar. I may have to put a block in the calipers and leave them unmounted to optimize the bleeder attitude. Wouldn't I still get pressure from the rear brake circuit?
 
JF900 said:
. Wouldn't I still get pressure from the rear brake circuit
Click to expand...
Front cir pressurizes the piston to activate the rears.

Only time the rear piston ( front brakes) contacts the front piston physically is when the front cir has 0 psi

What does your brake warning light do when you press the brake?
 
Dana - Wiring doesn't have power yet.

Thanks for everyone's help. I'll follow up on these thoughts tonight and let you all know what I find.
 
You can use a multimeter in the ohm scale between the post on the switch and the body .

If it reads low numerical numbers (1ohm etc.) the switch is closed and one system has no pressure. If it reads OL it is open and both systems have the same pressure.

Some meters have a feature where they beep when the leads are shorted. That would work well.
 
Well Rick you get the cigar. I should have taken notice that the bleeder was on the low side of the cylinder. I've bled alot of car and motorcycle brakes and clutches over the years, but sometimes you get distracted by things and don't see the forest for the trees.
Any way thanks to everyone's responses it truly is appreciated!
 
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