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Joined: Jan 2011
Posts: 152
Shade Tree Mechanic
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OP
Shade Tree Mechanic
Joined: Jan 2011
Posts: 152 |
Hi, when I depress the brake pedal slowly it goes right to the floor and does not activate the wheel cylinders. When I pump the pedal 3-4 times quickly the pedal stops about half way and I get a firm pedal with brakes activated. When I release the pedal and press it once it goes all the way to the floor. Everything in the braking system is new: master cylinder, wheel cyls, brake lines, junction blocks... and I have bled the system 5 times around the car going thru a liter of brake fluid. There are no leaks anywhere. Is this air in the system or do I have a problem with the master cylinder?
Thanks!
Mike
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Joined: Dec 2017
Posts: 69
Shade Tree Mechanic
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Shade Tree Mechanic
Joined: Dec 2017
Posts: 69 |
Sounds like you need to ajust brakes at wheel cylinders,Read repair Manual and follow instructions.
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Joined: Jan 2002
Posts: 30,701 Likes: 141
ChatMaster - 25,000
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ChatMaster - 25,000
Joined: Jan 2002
Posts: 30,701 Likes: 141 |
Sounds like a master cylinder problem. Fluid leaking past the check valve.
Gene Schneider
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Joined: Jan 2011
Posts: 152
Shade Tree Mechanic
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OP
Shade Tree Mechanic
Joined: Jan 2011
Posts: 152 |
Gene,
How would fluid leaking around the check valve when depressing the brake pedal result in no pressure and the pedal going to the floor? I understand the check valve holes regulate the flow/pressure of fluid out to the wheel cylinders and then the valve comes off it's seat when the pedal is released and brake return spring pulls back the master cyl piston faster than fluid can return from the wheel cyls. I would think a leaking check valve would result in more hyper active brakes. When I pump the pedal I am forcing more fluid in the lines and then the pedal holds which may align with what roberts39 is suggesting - the brake shoe clearance to the drum is too large and the wheel cylinders have to extend further to lockup the shoes?..
Thanks
Mike
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Joined: Jan 2002
Posts: 30,701 Likes: 141
ChatMaster - 25,000
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ChatMaster - 25,000
Joined: Jan 2002
Posts: 30,701 Likes: 141 |
Trust me - this was a common problem years ago.
Gene Schneider
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Joined: Dec 2007
Posts: 4,024 Likes: 99
ChatMaster - 4,000
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ChatMaster - 4,000
Joined: Dec 2007
Posts: 4,024 Likes: 99 |
Both are very plausible causes. Confirm that the brake shoe adjustment is correct at all wheels first. If the problem is still there then it is in the master cylinder.
Rusty
VCCA #44680
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Joined: Jan 2011
Posts: 152
Shade Tree Mechanic
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OP
Shade Tree Mechanic
Joined: Jan 2011
Posts: 152 |
absolutely, Gene has been spot on with all his advise over the years so I am not discounting it but the brake shoe adjust is a fast check compared to pulling out that master cylinder with clutch linkage (dumb design!). Thanks all for your advise :)
Mike
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Joined: Jan 2011
Posts: 152
Shade Tree Mechanic
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OP
Shade Tree Mechanic
Joined: Jan 2011
Posts: 152 |
just wanted to let you know the problem with by brake pedal going to the floor was because the shoe clearance adjusters were screwed all the way in and not adjusted as the mechanic told me. I adjusted the brakes as per Roberts39 suggestion and now the pedal stops about half way down and is firm. thanks for your assistance!
Mike
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