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Discussion Topic:
Soft brakes
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1934 Ford |
02-09-2016 @ 3:52 AM
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Senior
Posts: 567
Joined: Oct 2009
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I had friend with the same problem on a 1940 Ford Coupe. He discovered the brake drums had been turned to many times and would expand with pressure from the shoes. This was noticed with the car raises and one guy pressing the pedal, the other watching the drums. 75 years is along time to ask OEM Ford drums to last. Other drums solved his problem. Just another idea. 1934 Ford's since 1972
This message was edited by 1934 Ford on 2-9-16 @ 9:15 AM
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Dustbowl |
02-09-2016 @ 10:57 AM
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Posts: 74
Joined: Feb 2011
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Thanks for all the good suggestions, which I have followed up on as follows: -bled for air again with two man team -checked adjustment very carefully -found no expansion of rubber hoses -found no expansion of brake drum The only thing I have not done is remove the master cylinder to check honing. However, before doing that I would like to learn from you if there are any other possible causes of spongy brakes.
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40 Coupe |
02-10-2016 @ 6:52 AM
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Senior
Posts: 1647
Joined: Oct 2009
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There is a check valve at the tube end of the master cylinder it allows the fluid to return to the cylinder but maintains a slight pressure after. The valve has to be assembled with it's "rubber" seat. If the cylinder rebuild parts are not assembled properly the slight residual pressure will not be there and this will increase pedal travel. Below you will find the correct assembly sequence, even though this may not be your cylinder.
This message was edited by 40 Coupe on 2-10-16 @ 6:56 AM
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TomO |
02-10-2016 @ 9:26 AM
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Did you get any air out when you bled the brakes again? There have been a number of cases where the check valve in the kits are defective. Also, I would check the bore size. If the master has been rebuilt too many times the cup may not seat. I am not able to get to my reference material at this time to give you the specs, but I believe that the bore should not be more than .010 larger than the piston and that it must be consistent throughout the operating range. Rock Auto has the Raybstos rebuild kit and I believe that you can still buy the Wagner re-manufactured master cylinder from your local parts house, not a chain like Autozone.
Tom
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shogun1940 |
02-13-2016 @ 10:58 AM
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Posts: 464
Joined: Feb 2010
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If you step on the pedal and keep it down does it slowly go down to the floor ////. If it does then the primary seal is no good. There is a compensating port to let fluid behind the primary piston and cup if it is blocked then no fluid can get in and it will draw air in behind it causing spongy brakes
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supereal |
02-13-2016 @ 2:49 PM
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Bleeding old Ford brakes is always a chore due to the location of the master cylinder and the wheel cylinders. Bleeding with the old "pump and hold" method may take a gallon of fluid. We use a "power bleeder", and it takes just a few minutes. If possible, take the car to a place with one. It is also possible that the residual valve in your master cylinder is bad. This retains some pressure in the system so you don't have to pump the brake pedal every time you stop. If it doesn't hold, you will not get a good pedal however long you bleed.
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Drbrown |
02-14-2016 @ 9:12 PM
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Senior
Posts: 563
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39 Ken offers a good link to brake adjustment etc. The only thing I don't see mentioned in these posts is contained in my copy of the Ford Maintenance Manual .... when doing a major brake adjustment, have someone apply a constant (about) 30 lbs of pressure on the brake pedal while adjusting the anchor bolts at the bottom of the shoes. THEN adjust the cam bolts.
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39 Ken |
02-15-2016 @ 5:35 AM
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Posts: 380
Joined: Oct 2009
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"when doing a major brake adjustment, have someone apply a constant (about) 30 lbs of pressure on the brake pedal while adjusting the anchor bolts at the bottom of the shoes" I've only heard of this procedure in reference to mechanical brakes, not to hydraulic brakes.
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Drbrown |
02-15-2016 @ 6:40 PM
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39 Ken .... I transcribed that text about ".... 30 lb pedal pressure ...." from my "1942-1948 Ford/Merc Shop Manual", Chapter E, Beginning on Page E-4 titled "Hydraulic Brake System". Go to Page E-8 "To Adjust Brakes" Paragraph "1. Apply approximately 30 lbs to the foot pedal. This pressure must be maintained throughout this adjustment. ..." The section goes on to describe adjustment of the lower Anchor Bolt. The same page includes images of related hydraulic brake wheel assemblies. My Shop Manual is a Ford Motor Co reproduction. Unless it was reproduced incorrectly, or later amended, I assume its correct.
This message was edited by Drbrown on 2-15-16 @ 6:42 PM
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39 Ken |
02-19-2016 @ 4:21 AM
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Drbrown, You're correct that the procedure that you describe is a Ford procedure per their Manual. I've always gone by my Chilton manual which doesn't include that procedure to apply 30 pounds pressure to the foot pedal. Yesterday, I did find that your procedure is contained in a Ford service bulletin. Also, I had lunch with a friend that has wrenched on cars since the mid fifties and he learned that procedure "way back when" while working on Willy's Jeeps. Apparently that procedure isn't exclusive to Ford. I don't know how often it is used, but apparently, either way does the job. Thanks for clearing that up. Ken
This message was edited by 39 Ken on 2-19-16 @ 4:22 AM
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