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620 1978 brake booster


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Whats up guys ! I am currently rebuilding my truck and trying to finish the brake system but I'm having a hard time trying to find parts .. I changed both master cylinder because they were leaking and when arrived the time to put the new master on the booster I found a lot of brake fluid inside and the oil was black so I assume the diaphragm is bad now. I called every autopart and tried a bunch on internet and can't find it . part number I found on rockauto is 53-5240 but it's discontinued . My question is ; Does anybody ever fit another booster on this truck that would still be available ? If not I think I will just delete it ..

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Why not clean and test it? Brake fluid does not attack anything rubber so why assume it's bad?


Pump pedal several times and hold down. Start engine. What you should notice is the pedal immediately drops slightly. If it does, it's working.

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Probably from the master. Rinse out with brake cleaner.


The brake booster increases the brake line pressure up to double, or halving the effort. Removing the booster is a bad idea as the effort increase will be dramatic and tiring. Try a want ad here on Ratsun or a wrecking yard for a used one.

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