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Master cylinder pushes fluid out the top


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Hi Scotty I have a 1981 f250 that has an issue with pushing brake fluid out of the top of the master cylinder. Practically a brand new brake system...brand new master cylinder, brake booster , new proportioning valve, new driver side wheel cylinder but it's still pushes fluid out of the top when hitting the brakes. Only a minor amount but I know it shouldn't be doing that...the truck has a 460 out of a 70s vehicle the truck itself was originally the 300 i6 does swapping the engine have anything to do with that? 

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1 Answer

What would you have to figure out is is it pushing it out when you push on the brakes or when you release the brakes. If it doesn't when you push the brakes then the master cylinder is not selling the fluid out correctly and that would be the fault. But if it did it when you release the brakes that would mean there was a problem with the booster or built up pressure in the system that's leaking back and then coming out the top