| Dustbowl | -- 02-05-2016 @ 3:48 PM |
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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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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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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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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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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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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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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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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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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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Have you checked the rubber hoses tha could be expanding and not breaking
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| 1934 Ford | -- 02-09-2016 @ 3:52 AM |
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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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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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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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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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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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"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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| Drbrown | -- 02-20-2016 @ 9:29 PM |
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39 Ken .... I never came across that procedure either until recently. It makes sense with this particular style of brake set-up. I suspect applying pressure to the top of the shoe forces it downward so the shoe at the lower anchor bolts can be more tightly positioned against the drum. Then the side cams can be rotated to more accurately position the shoes against the drums.
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