| Jone | -- 09-08-2019 @ 7:05 AM |
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Yesterday, while driving my '47 Mercury home from a club tour, I was descending a hill. When I stepped on the brake pedal it hit the floor, no brakes! I shifted down and safely rolled to a stop. After pumping the brake a few times and the brakes returned to normal and I was able to drive 45 miles home with good brakes. Just prior to going down the hill, I had gone up a steep grade. Can anyone tell me what might have caused the brakes to momentarily fail and then return to normal
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| TomO | -- 09-08-2019 @ 9:04 AM |
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Your master cylinder may be low on brake fluid. If it is, I would check all of the wheel cylinders and pull back the boot on the master cylinder to check for leaks. If the cylinder has fluid, then I would replace the master cylinder. Tom
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| Jone | -- 09-21-2019 @ 2:52 AM |
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Finally got "a round tuit" and checked the master cylinder. It is full of brake fluid and the fluid is clear. The master cylinder is five years old. I don't believe I had used the brake enough to heat up the fluid that day.
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| TomO | -- 09-21-2019 @ 7:00 AM |
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To avoid another scary drive, I would replace the master cylinder. It has given you warning that it is going to fail completely soon. Are you using DOT 3 brake fluid or silicone brake fluid? Tom
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| 37RAGTOPMAN | -- 09-21-2019 @ 1:04 PM |
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hi 47 merc brakes, try applying slight pressure on the brake pedal, do this while just sitting there, if it starts to go down, if it does the master cylinder is bad, the fluid is passing the piston, pull the rubber boot off and see if these is any signs of fluid brake fluid, if only need a few drops, well worth the effort to check it out, I had the same thing happen to me using silicone brake fluid, never using that again, hope this helps, 37Ragtopman This message was edited by 37RAGTOPMAN on 9-22-19 @ 10:46 AM
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| CharlieStephens | -- 09-21-2019 @ 1:06 PM |
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I assume you checked everywhere and didn't find any fluid leaking. Try posting your question on HAMB, https://www.jalopyjournal.com/forum/forums/the-hokey-ass-message-board.5/ You will get a lot more people looking at it there. I can't figure out a scenario that would explain the problem you describe, maybe a few more people looking at the problem. By the way, are the brakes the same as Ford brakes? Charlie Stephens
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| TomO | -- 09-23-2019 @ 7:42 AM |
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Any time that the brake pedal goes to the floor when the master cylinder is full of fluid, it is a failure of the piston and its seals in the master cylinder. The fix is to rebuild or replace the master cylinder. From experience (over 70 years of driving), I can say for sure that this will happen again and no amount of pumping will make the brakes work again. 37Ragtopman, this can happen with any brake fluid and it does happen more often when there is excess moisture in the brake fluid. Tom
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| Jone | -- 09-30-2019 @ 7:30 PM |
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I'm using DOT 3 fluid. I will rebuild the cylinder, even though it's only 5 years old. Better to be safe than sorry. Thanks for all the help and comments.
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| TomO | -- 10-01-2019 @ 7:43 AM |
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When you use DOT 3 fluid, you should flush the system on an annual basis. I suggest every Spring after you take the car out of storage. If you don't store it for the winter, and drive it frequently all year, you could get away with doing it every other year. DOT 3 accumulates water and water is bad for the system. It lowers the boiling point of the fluid, it corrodes the cylinders and decreases the life of the rubber parts. Tom
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