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Thread: Hydraulic Brake System

  1. #1
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    Hydraulic Brake System

    Am having doubts about the hydraulic brakes on my '76 Impala.
    When I first apply the brakes, at any speed, I would say, "fine", meaning it's working OK. ...But....

    When I release pressure a bit, then continue to depress, the pedal goes down about a quarter inch or so, and keeps on going down as I apply more pressure, and I believe pedal will go ALL the way to the floor board.

    Can anyone give me a detailed diagnosis ?
    I thought the master cylinder was low but topping it off did not solve the loss of brake reserves.

  2. #2
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    Your master cylinder is leaking (internally), sort of like a piston with no piston ring.
    They are rebuildable, but it requires skill and special tools that you probably don't have, and if it's as old as the car, it could have problems that make it not rebuildable.
    Replace it.

  3. #3
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    Thanks for the update, mike. Safer to replace it I concur. I brought the problem to my mechanic to see if it would solve the problem, I mean we topped it offbut the prob is still there.

  4. #4
    Senior Member grouch's Avatar
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    The internal cups in your master cylinder have split. It WILL get worse. Soon it will feel like stepping on a rotten plum and the brakes won't work. Your master cylinder is fairly easy to replace. If it takes your mechanic an hour to change it, he took a nap in the middle of the job.

    I would check all the rubber parts in your system though. You have two flex hoses in the front and one in the rear. If they show cracks in the rubber, replace them. It won't hurt to pull the rear wheels and drums and take a look at the wheel cylinders. I did that on an RV I've got and saw some seepage. When I removed it, it fell apart.
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  5. #5
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    I had my mechanic replace the cylinder yesterday. I thought a new M. cylinder would be difficult to obtain for my 35 plus year old car but I worried for nothing. He had the whole hydraulic system checked and the brake shoes and both wheel cylinders replaced about a year ago but checked them again when he installed the new M. cylinder. My car has rear shoes and drums and disc brakes in front.

  6. #6
    Senior Member grouch's Avatar
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    Quote Originally Posted by ChevyMan View Post
    I had my mechanic replace the cylinder yesterday. I thought a new M. cylinder would be difficult to obtain for my 35 plus year old car but I worried for nothing. He had the whole hydraulic system checked and the brake shoes and both wheel cylinders replaced about a year ago but checked them again when he installed the new M. cylinder. My car has rear shoes and drums and disc brakes in front.

    Your car has the bread and butter brake system that was used for years on cars and trucks. The only time you have odd parts on a 1970's or 80's GM car is if it had a diesel engine when it was new. Most of those have had gasoline engines retrofitted over the ears. I did several myself when they were only a few years old. You can tell an ex-oil burner by the hydroboost brake booster rather than the vacuum booster.

    Trim and body parts might be getting scarce but the mechanics will be easy to get for your cars.
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  7. #7
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    Then I guess if I had to replace, say , parts like 4 bbl carbs, starter motors, electric door window opener motor assembly, I could easily replace if needed ?

  8. #8
    Senior Member grouch's Avatar
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    Quote Originally Posted by ChevyMan View Post
    Then I guess if I had to replace, say , parts like 4 bbl carbs, starter motors, electric door window opener motor assembly, I could easily replace if needed ?

    The door window motor might be a bit fun but the rest, sure thing. Starters are common and if a rebuild kit isn't available for your car, an aftermarket carburetor is. The 350 engine is the sweet heart of street rodders.
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