1940 120 master cylinder

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1940 120 master cylinder

Post by Packard-Henney » Mon Nov 28, 2016 5:43 pm

I am having a problem with the brakes gradually tightening up on my 1940 120. I believe it to be the bleed back orafice in the master cylinder stopped up. Is there any way to run a drill or wire in the orafice while the cylinder is still on the car? I did it on a 1952 Pontiac and it cured the problem. Thanks!

Dave Czirr
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Re: 1940 120 master cylinder

Post by Dave Czirr » Mon Nov 28, 2016 6:43 pm

A more likely possibility is lack of pedal free play.

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Re: 1940 120 master cylinder

Post by Howard56 » Mon Nov 28, 2016 7:51 pm

Others have had issues with the small orifice in the compensating port (item K in illustration) closing. The size of the orifice is approx .025 to .028 and several have successfully cleaned and made the cylinders function properly by using a length of piano wire or a drill bit close to that size to restore the opening.

I believe the 1940 cylinder is the same as this later illustration so the port should be visible almost directly under the fill cap and reachable with a length of piano wire while still in the car.

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