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Discussion Topic:
40 Deluxe brake system question
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2manybikes |
12-28-2021 @ 6:54 PM
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Member
Posts: 39
Joined: Sep 2021
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40 Coupe, Thank you for replying. Since my initial post, I have learned quite a bit more than I did when I started. A better description of my issues is losing my "free play" and travel to a fully depressed pedal. My return spring is present and accounted for. I sat in the car and pushed the brake pedal down 100 times, stopping every 25 and checking to see if the brake lights came on. They did not. I think that cancels out the theory of a plugged hole in the bore. I even put some unnecessary slack in the emergency brake cable, and adjusted the rod at the master cylinder out another 3/16" or so. Still did the same thing in about 5 miles. I moved it another 3/16" or so but was unable to try that before dark. A couple days of rain in the forecast so I will report back when I can. Is it possible to overfill the master cylinder leaving no room for expansion if the fluid heats up? Once the car sits for an hour or so the "pressure" in the system drops, the lights go off and the pedal returns to a "normal" state.
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TomO |
12-28-2021 @ 8:05 PM
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Senior
Posts: 7250
Joined: Oct 2009
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Do you have the correct free play of the brake pedal? Until you have it, we cannot give you further advice.
Tom
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40 Coupe |
12-29-2021 @ 5:12 AM
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Senior
Posts: 1673
Joined: Oct 2009
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Here is some reading for you. Note how the pressurized brake fluid returns to the master cylinder fluid reservoir and how the piston can block the very small return hole if the brake pedal adjustment is not correct or the return spring is improper.. While driving heat can build up in the brake system expanding the brake fluid. There is a check valve at the fluid output end of the master cylinder it allows a residual very small pressure to stay in the brake lines. Any pressure in the brake lines in excess of the slight residual has to bleed back to the MC reservoir or the brakes can start to bind up and the brake lights will stay "ON".
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2manybikes |
03-07-2022 @ 4:30 PM
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Member
Posts: 39
Joined: Sep 2021
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The weather has been nasty for so long its hard to remember being outside. I got the car out finally a couple days ago. I think my brake adjustment rod is close to where its supposed to be finally. This may be a hard question to answer but can anyone explain to me, or have a photo of the left side exhaust manifold pipe routing in relation to the master cylinder? I'm having issues with transferring photos from my phone to the computer or I would post what mine looks like. Basically mine runs under the frame below where the master cylinder mounts.
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TomO |
03-08-2022 @ 8:46 AM
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Senior
Posts: 7250
Joined: Oct 2009
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I like to route the pipe through the frame and along side the left side frame rail. The best size pipe for the left side to do this, is a 1 1/2" pipe. A 1 3/4" pipe is the largest that will work on the left side. I have photos of my Mercury's left side pipe but they won't do you much good as the frame on the Mercury is different from the Ford in 1939 and 1940. As long as you have at least 1/2" clearance between the exhaust pipe and the master cylinder, the exhaust heat will not affect the brake fluid temperature. The brake fluid will heat up and expand with brake usage and the correct free play is critical. I am hard of hearing and I can still hear the pushrod contacting the master cylinder piston when I adjust the freeplay.
Tom
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2manybikes |
03-11-2022 @ 4:13 PM
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Member
Posts: 39
Joined: Sep 2021
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TomO: Thanks for another reply to my numerous questions. I hope to get back on the car next week.
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