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EFV-8 Club Forum / 1940 Ford Discussion / Brake system lock-up issue

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Posted By Discussion Topic: Brake system lock-up issue -- page: 1 2     Drbrown 07-29-2023 @ 8:08 AM reply profile send p.m. Senior Posts: 570 Joined: Nov 2013 Couple days ago, after driving a small ways and returning home, I sensed the brakes groaning (engaged) when parking and noticed the brake lights stayed on, even after turning the car off. So disconnected elec system to avoid a dead battery and it sat for several days. Today all back to normal. I see not leaks and doubt such given the brakes are activating. I've had the car 10 years, understood system was rebuilt then, only put about 1000 miles on it and been thinking I should have the system flushed. Question: How do I tell which DOT fluid is in system ? (i.e. color ?) I should know this before having system flushed or working on it. Thought: If system pressure was not releasing, is it likely a problem with the master cylinder ? trjford8 07-29-2023 @ 8:41 AM reply profile send p.m. Senior Posts: 4214 Joined: Oct 2009 First make sure your brake pedal return spring is attached and working. From there I would look at the master cylinder. Remove the cap and see if fluid is returning after the pedal returns. You will see some bubbling of the fluid at the return port in the cylinder. If all looks O.K. then go to the wheel cylinders. Have a second person push on the pedal and release it. Then see if you have a wheel that does not want to move. If all four wheels lock up I suspect it's your master cylinder. As a general rule if you have fluid with a purple tinge it usually means you have silicone fluid. Regular brake fluid will lift paint, so you could test it by putting a drop or two on a sample piece of painted metal. kubes40 07-29-2023 @ 8:43 AM reply profile send p.m. Senior Posts: 3394 Joined: Oct 2009 Most likely one of two issues. Perhaps both. 1) Master cylinder rod is adjusted too long. That causes a delay or even a stop in the fluid being allowed back into the master. the brake pedal will become harder each time you press it down. Let it sit overnight and most likely, the pedal will feel fine. 2) Brake shoes are adjusted too close to the drums. Shoes heat up and drag. I'd start at the master rod. Mike "Kube" Kubarth Drbrown 07-29-2023 @ 8:56 AM reply profile send p.m. Senior Posts: 570 Joined: Nov 2013 Thanks to all. The brake system had been working fine; good solid pedal and even stopping. I wonder to myself if the lock up was a fluke i.e. the pedal or MC rod didn't properly return .... at the incident I didn't look at or feel the pedal for any free-play. I'll look at the items suggested and jack the car to make sure each wheel is braking. I found Tom'Os old post with copies of factory manual on how to do adjustments. This message was edited by Drbrown on 7-29-23 @ 8:58 AM Drbrown 08-08-2023 @ 12:50 PM reply profile send p.m. Senior Posts: 570 Joined: Nov 2013 Concern regarding my apparent system lock-up event remains unexplained. Had system inspected and flushed. Installed self-bleeding fittings at wheel cylinders. Master cylinder looks and functions fine. Pedal and master cylinder rod freeplay were and are at what they should be. Wheel cylinders function and no leakage found. Brake shoes still set at proper positions. The system had not been flushed in 12 years or more. The brake pedal now feels stronger than before. kubes40 08-08-2023 @ 2:55 PM reply profile send p.m. Senior Posts: 3394 Joined: Oct 2009 It would have been prudent to disassemble each wheel cylinder. After twelve years, there's a great chance that one or more are "gummed up". Although the issue you had has not reoccurred, my money is on "it will". You might be amazed at how corroded the cylinders can become. Mike "Kube" Kubarth RAK402 08-08-2023 @ 7:23 PM reply profile send p.m. Member Posts: 436 Joined: Jul 2015 DrBrown, I have to ask-What are self-bleeding brake fittings? Drbrown 08-09-2023 @ 11:03 PM reply profile send p.m. Senior Posts: 570 Joined: Nov 2013 RAK402: As best I can describe ..... With stock air bleeder fittings at the individual wheel cylinders, it takes two persons to bleed air out of the brake system through the individual wheel cylinders ..... one person to apply and keep a steady pressure at the foot pedal and one person under the car to open and close the bleeder valve to release any trapped air out of each wheel cylinder. If the fluid runs low during this procedure or foot pressure is removed from the pedal, air can get sucked back into the cylinder thru the open valve. By replacing the stock bleeder valves with the so-called self-bleeder valves only one person is needed to do the operation. The self-bleeder valves at the cylinders have an internal valve that closes when foot pressure is removed thus preventing air from being sucked back in. SO one person can open the self-bleeder fitting at a wheel cylinder then go top-side and apply pressure on the foot pedal to force air out the bleeder. The master cylinder must be kept full at all times when doing this. So as normal, start at the wheel furthest from the master cylinder and attach a drain hose to the valve to collect the fluid in a container. Apply pressure to foot pedal enough to assure that all air at the wheel cylinder has been forced out. Keep master cylinder full. Tighten valve fitting at wheel when done. You should have a good solid feel when applying the brake pedal. I bought the self-bleeder fittings (two to a package) several years ago from one of the Ford suppliers. Be sure to get the ones with the correct tread size. This message was edited by Drbrown on 8-10-23 @ 10:05 PM Drbrown 08-09-2023 @ 11:09 PM reply profile send p.m. Senior Posts: 570 Joined: Nov 2013 kubes40: I agree. We did collect the fluid individually from each wheel cylinder and inspect it. To the good, the fluid did not show any moisture or decoloring. kubes40 08-19-2023 @ 7:31 AM reply profile send p.m. Senior Posts: 3394 Joined: Oct 2009 The fluid will most likely not show any issues. The pistons are where the issue shows up. Ya can't know until the wheel cylinder is disassembled. I'd place a healthy size bet; the cylinders are not "healthy". There may very well be a lot of white corrosion built up at the cylinders. That hinders the travel of the piston. As it gets worse, the piston will be forced out (hydraulic pressure) but will be unable to retract properly. Mike "Kube" Kubarth This message was edited by kubes40 on 8-19-23 @ 5:21 PM

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