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Did my brake master cylinder failed today

Did my brake master cylinder fail?  

15 members have voted

  1. 1. Did my brake master cylinder fail?

    • Probably, yes
    • Unlikely
    • Cannot tell from details provided

4 posts / 1429 viewsLast Reply

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Did some research in the forum but i wanted to ask as well.

While giving a tour of SF to some of my girlfriend's family in the 74 Tii, I noticed my braking power was getting weaker. After a few more stop signs, I noticed the brake pedal could hit the floor and the braking power had decreased significantly.

With a combination of brake pedal and hand brake I limped the car home. By the time I got home the pedal would easily make it to the floor while providing no braking power at all.

I checked the brake fluid reservoir and it was still full.

So the points are:

1) Pedal easily reaches floor with no braking power produced

2) No loss of brake fluid

3) No uneven braking

4) Girlfriend's family was impressed by my ability to parallel park only using the hand brake.

So has my brake master cylinder failed? Is there a way to test to make sure my vacuum assist isn't the culprit?

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My son's 74 was doing the same, at a stop the brakes worked but constant pedal pressure sent the pedal to the floor , pumping the brake helped , I checked wheel cylinders for leaks, none , no fluid loss at calipers, no fluid loss from resevoir. Classic M/C fail,we changed the m/c now great brakes with consistant hard pedal , as it should be. Amazon to the rescue with a M/C.

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Voted probably yes....

When you go to replace it be sure there isn't any brake fluid in the booster. I know you said that it hasn't lost any fluid, but it's better safe than sorry.

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1. Make sure your brake booster is functioning properly--check the hose (esp the little one between the check valve and manifold) for leaks...if your idle has suddenly gone wonky, that's a clue that there's a vacuum leak.

2. If the booster checks out, then suspect the M/C. They often fail internally, allowing fluid to pass the pistons/seals (thus no pedal) but not leaking externally. Had one fail with less than 25k on it some years ago.

Not terribly difficult to replace, just remember to bench bleet the M/C before installing, then connect all the brake lines to the M/C--at least two or three threads--before bolting the M/C to the booster--much easier to do it that way. And a power bleeder will make bleeding the system much easier.

cheers and happy tinkering


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