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Discussion Starter · #1 ·
ok all of a sudden my brakes are gone, er well kinda. if i push the pedal it goes all the way to the floor with very little resistance, but it does apply them some. I knew the pads were low so i bought a new set. the fronts were practically metal metal, the rear's about half the life left to them. new fronts and turned rotors, rear's didn't need turning left em on with the old pads, bled them all the way around. get back in and the same thing happens pedal to the floor. if i pump it i get more resistance building up but it looses pressure quickly. checked the master cylinder, no leaks full of fluid. all the vaccume hoses apear to be in place and in good shape. anyone got an idea?
 

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Re: i know my car is old, but is it supposed to have flinstone brakes? (Clav)

Sounds like either air in the system, or possibly the master cylinder.
Try bleeding it first. If it's just air in the system, bleeding it will fix the problem. Be careful when you bleed it and don't push the pedal more than half way to the floor.
After changing the pads, did you pump the pedal back up with gentle pumps 1/2 way to the floor until the new pads engaged? Or did you push it all the way to the floor?
When the master cylinder is old, there's often corrosion and/or junk in the front part of the master cylinder bore. The part that gets "normal use" is still polished and smooth, but the part beyond where you normally push the pedal will get corroded and junked up. If you push the pedal to the floor, either while bleeding the thing or when you put new pads in and the pistons are still retracted and there's no resistance or pressure, you can push the rubber seals on the master cylinder piston over this corroded, junky part of the master cylinder and it can grind/cut the seals and damage them. The only solution is to replace or rebuild the master cylinder.
 

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Discussion Starter · #6 ·
Re: i know my car is old, but is it supposed to have flinstone brakes? (Racer_X)

when i beld it i had my buddy press the pedal and yes he did go all the way to the floor. and after putting in the new pads i pumped it a few times, but each one to the floor or as far as it would go since it started building up pressure. i'm guessing master cylinder too. Anyone know if you ca go to the bigger mastercylinder without upgrading the rest of the brakes?
 

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Re: i know my car is old, but is it supposed to have flinstone brakes? (Clav)

yes you can. all the MC does is create the pressure in the lines to squeeze the pads together. a 22mm MC creates ~20% more pressure than the 20mm, squeeaing the pads together with more force.
 

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Re: i know my car is old, but is it supposed to have flinstone brakes? (Halo8)

A bigger mastercylinder gives less pressure but more volume, ie, the pedal moves less but requires more foot pressure for the same effect.
 

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Re: i know my car is old, but is it supposed to have flinstone brakes? (Vdubs)

Quote, originally posted by Vdubs »
Mastercylinder.

That's exactly what i was going to tell you. With the car over 12 years old things happend like that. put a 22mm MC and you will have much better brakes and will not have to worry aout it. It doesn't cost that much and direct bolt in.
 

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Re: i know my car is old, but is it supposed to have flinstone brakes? (Clav)

Quote, originally posted by Clav »
when i beld it i had my buddy press the pedal and yes he did go all the way to the floor. and after putting in the new pads i pumped it a few times, but each one to the floor or as far as it would go since it started building up pressure. i'm guessing master cylinder too. Anyone know if you ca go to the bigger mastercylinder without upgrading the rest of the brakes?
You can, but the 22mm master cylinder is a downgrade if you don't change the calipers. It takes 20% (about) more pedal pressure to get the same braking force if you use the 22mm master cylinder (compared to the stock 20mm master cylinder).
Larger master cylinders reduce the pressure in the hydrualic system, but they do provide more fluid flow which is often necessary with larger calipers. You are applying the same force (pounds) to a larger area (more square inches), so the overall pressure will be lower (pounds per square inch).
As part of an upgrade with larger calipers, larger master cylinders are often necessary. But you generally get more increase in braking force from the larger pistons in the larger calipers than you lose to the larger master cylinder. So overall you'll get a better package that way. But the larger master cylinder is only used because it's necessary to prevent the pedal from going to the floor before the calipers fully engage and reach full braking force.
 
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