| Dustbowl | -- 05-18-2015 @ 5:14 PM |
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Gradually over time, I find my brake pedal goes too far near the floor when stopping but will stop half way to the floor if I double pump it. In both cases, the car stops well. First, I adjusted all the brake shoes as per manual; all brake shoes are good. Then, suspecting air in the system (even though master cylinder is full and problem gradually developed), I bled brakes at all four wheels. No improvement. Next I removed master cylinder and rebuilt it (and put it back full with fluid) and also one rear wheel cylinder. And I bled all brakes again. No improvement. Changing adjustment on the master cylinder plunger does not help. After all that, the brakes still perform just as when I started. What is my solution? More bleeding? something else? Help!
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| 1934 Ford | -- 05-18-2015 @ 6:12 PM |
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I'm not sure what your problem is, but once I had a spongy pedal in an old Ford and discovered that the drums had been turned to many times and the drums flexed when the pedal was applied and I could feel it in the pedal. 1934 Ford's since 1972
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| Drbrown | -- 05-18-2015 @ 7:56 PM |
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x2 34 Ford .... No mention of apparent leakage. Otherwise, general rule of thumb: Spongy pedal = air in lines. Firm pedal but low to floor (pumped-up or not) = out-of-adjustment or worn shoes and/or drums. If you back-off the shoe adjustment clearances per manual, pedal travel should be okay. Does hand brake work correctly ?
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| ford38v8 | -- 05-18-2015 @ 8:32 PM |
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You know you've got Big Trouble when the pedal sinks to the floor... while you're stopped at an uphill red light in San Francisco... with a Cadillac stopped right behind you! (ask me how I know) Alan
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| TomO | -- 05-19-2015 @ 6:15 AM |
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First, you should tell us what year car you are working on. Brake pedal free play is an important adjustment. This is what you called the plunger adjustment. If you do not have the minimum free play of 1/4", your brakes will not fully release because the piston is still covering the bypass port. Tom
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| Dustbowl | -- 05-19-2015 @ 12:21 PM |
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To respond to commenter's questions, my car is 1936 with 39 or later juice brakes. And the hand brake works well. I appreciate the comments but I fear that I have not had a true expert address my somewhat bizarre problem. Of course my first reaction, as you have suggested, is that there is air in the system. And, with that in mind, I have pumped more than four quarts of brake fluid through the system, with no success. And I raised doubt over air because this problem gradually increased from very good brakes to bad without the system being opened or it running low on fluid in the master system. So how could air get in? So, while I don't discount air by 100%, I sense there is some other mechanical related problem. And it is not brake shoe adjustment nor master cylinder plunger adjustment. Please let me know if I am being too stubborn in my perspective and if I should just do more on air removal.
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| shogun1940 | -- 05-19-2015 @ 2:46 PM |
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ok if the pedal goes down to far then it is not pushing fluid, if the air is in the system it makes a spongy brake.. when you pump the brake up does it go down slowly that would mean the main seal is leaking. the master cylinder has two ports in it, one in front of the seal a smaller one to compensate behind the seal.. the seal traps fluid when compressing , but fluid will go around the edges as it retracs . take the master apart and check where the seal is and that both ports are clear. have fun
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| ldh2176 | -- 05-19-2015 @ 4:22 PM |
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You did not state just how you bled the brakes but I will assume it was in what I have found to be in the right order. Start at the right rear then left rear, right front then left front. This has always worked for me in getting the most air out of the system. Good luck.
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| ford38v8 | -- 05-19-2015 @ 10:49 PM |
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Tell us the exact method you used to bleed your brakes. Tell us also, what type of brake fluid you are using. We are flying blind here, very difficult to diagnose a problem long distance. Alan This message was edited by ford38v8 on 5-20-15 @ 7:35 AM
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| TomO | -- 05-21-2015 @ 7:23 AM |
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You said that the brakes gradually went from very good brakes to bad brakes. In order to help you we need the answer to a few questions. How long did it take for this to happen? Example of answer: 1,000 miles, a couple of hours in stop and go traffic? What kind of brake fluid are you using? Is the pedal low but hard or low and spongy? When you inspected the brake shoes was the wear pattern even along the shoes? Tom
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| 40 Coupe | -- 05-22-2015 @ 4:02 AM |
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At this point you may want to identify exactly what brake backing plate you have. IMO you should look at the adjustment. The 39-42 has four adjusters on each plate and the 46-48 has only two. I suggest you do a quick adjustment (front shoe first) leave each shoe with a very slight drag. See if this helps.
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