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Discussion Topic:
Soft brakes
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Dustbowl |
02-05-2016 @ 3:48 PM
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Member
Posts: 74
Joined: Feb 2011
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I have done much work on the hydraulic brakes (1939 Ford version) in my 1936 Ford. This includes rebuilding the master cylinder. The brakes stop the car all right but: - the pedal seems "soft", like air in the system, and - the stopping distance seems too long, and - even when pushing hard on the pedal, I cannot lock the brakes (and cause wheels to slide) Suspecting air, I have done extensive bleeding of the brakes by pumping (using the brake pedal) at least one quart of brake fluid or more through each wheel. My questions for you: -If you best guess is air, what can I do to remove it? -what other faults in my braking system might cause the problem I describe above? -what other tests might I make to identify the problem? (For example I have thought of installing a pressure gauge in the hydraulic lines to see if I get enough pressure. If I do, what should be the correct pressure?) Any thoughts or advice will be greatly appreciated. Phillip
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CharlieStephens |
02-05-2016 @ 4:56 PM
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Senior
Posts: 893
Joined: Oct 2009
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Are you using DOT 5 fluid? How about a detailed step by step of how you are bleeding the brakes? Charlie Stephens
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Dustbowl |
02-05-2016 @ 5:30 PM
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Member
Posts: 74
Joined: Feb 2011
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These are my answers Charles: -I am using DOT 3, not 5. -To bleed, I attach a plastic tube to the brake nipple and ensure it is not leaking or sucking in air -tube sticks in container submerged in brake fluid -keep adding fluid into master cylinder to ensure level does not get low. -open the nipple -pump brakes until I am sure no bubbles coming through and then pump another pint or more through. =close nipple when tube is still full of fluid -repeat on each wheel. -when finished, I double check for leaks. I have tried using a "Power" system but don't have a good connector from power tube to master cylinder which does not leak. What do you think?
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TomO |
02-05-2016 @ 8:11 PM
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Senior
Posts: 7256
Joined: Oct 2009
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You might still have air in the system. I would start with the 2 man brake bleed. Have one man press the pedal while the other opens the bleeder, hold the pedal to the floor and close the bleeder. You should be able to clear all of the air at a wheel with 4 openings. If you cannot accomplish this, try bench bleeding the master cylinder. You may have to recheck the honing of the master cylinder Tom
This message was edited by TomO on 2-5-16 @ 8:14 PM
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MICHV8 |
02-06-2016 @ 3:19 AM
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Posts: 448
Joined: Jul 2010
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just like with home plumbing, start with the longest line (usually the passenger rear) and continue toward the shortest. Does the pedal maintain pressure? If not, the piston is moving through the bore...
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39 Ken |
02-06-2016 @ 5:25 AM
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Posts: 380
Joined: Oct 2009
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The problem could be improper adjustment; not enough surface contact between the shoes and the brake drum. Assuming new shoes, the long shoes need to be on the front of each wheel, and the short shoe to the rear of each wheel. Here is a link to the proper adjustment of the Lockheed brakes. http://www.flatheadv8.org/rumblest/brakes.pdf
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40 Coupe |
02-06-2016 @ 6:42 AM
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Senior
Posts: 1679
Joined: Oct 2009
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If you have not done the basic mechanical adjustment at each wheel, I suggest you do that first before bleeding. You can do the mechanical adjustment again after bleeding. Why do you have to bleed the brakes what work have you done to warrant this?
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mrtexas |
02-06-2016 @ 7:01 AM
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Posts: 68
Joined: Dec 2011
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Good pedal is impossible without proper shoe adjustment. Have the shoes been arced to the drums?
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ford38v8 |
02-06-2016 @ 4:10 PM
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Senior
Posts: 2764
Joined: Oct 2009
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Previous advice is all good, however, due to environmental regulations, the excellent properties of the old asbestos shoes are no longer available from automotive sources. The modern replacement material contains a large percentage of brass chips to slow the wearing of the asbestos. This is true of shoes and also of disc pads, and explains some brake squeals and chirps. A Google search may reveal an Industrial Friction Products company with the ability to apply the old product to your shoes.
Alan
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shogun1940 |
02-07-2016 @ 10:07 AM
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Member
Posts: 464
Joined: Feb 2010
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Have you checked the rubber hoses tha could be expanding and not breaking
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