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PV Brake lock up 444-544

posted by  someone claiming to be PVGuy on  Thu Jun 5 13:21 CST 2025 [RELATED]

In hot weather the drum brakes on my 1962 PV 544 tend to lock up. When I restored the car I replaced the master cylinder. I've also replaced all wheel cylinders and the rubber final flex hoses to the wheel cylinders.
Seems that the heat, either engine or ambient 80's, causes the brake fluid to expand and not release when I take my foot off the brake?? Is there something in the master cylinder that would cause this? I put in a new one. I also made sure that the small hole in the fluid container was open and not plugged. But interestingly, there is a small amount of fluid that pushes out of this hole when it happens.








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    PV Brake lock up 444-544

    posted by  phonemanjames on  Thu Jun 5 16:21 CST 2025
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    last visit: Thu Oct 23 20:02 CST 2014
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    Just out of curiosity, do you have the brakes "arced" before installing them. If not, then in combination of brakes fluid expanding, pushing on the brake pads, you may have a leading or trailing edge of the brake pad pushing against the drum. I know i am spit balling here, but I've seen some crazy things happen on here.








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    PV Brake lock up 444-544

    posted by  Dave Stevens on  Thu Jun 5 14:28 CST 2025
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    last visit: Sun Jan 1 02:36 CST 2012
    [RELATED]

    There is air in your brake system that is expanding under heat and causing the brakes to set and the master reservoir to backfill and overflow. As you just changed the master cylinder, begin by bleeding the MC (you can look up online how to do this) then bleed the brakes in the proper sequence (preferably using a pressure or vacuum power bleeder tool rather than the brake pedal). Power bleeding helps protect the MC seals and will do a better job of pushing/pulling any air locks out of bends and crevices in the system.
    --
    Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now







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