Auto Parts: Brake Leak from Master Cylinder Cover?, power disc brakes, pep boys

Question
Hello,
I've noticed on my 1970 Dodge (Power Disc Brakes in front, drum in rear) that after driving for awhile I can see small streaks of brake fluid that look to have seeped out from the Master Cylinder cap.  Not a lot of brake fluid gets out ... but I can see the streaks and wipe them off.  I haven't noticed a sizable drop yet in fluid levels in the master cylinder, but over time, I suppose this amount will add up.

I have tried replacing the Cover and Gasket, but still notice faint streaks after the car is driven.

Do you think it's time for a new Master Cylinder?  And do you think the fluid gets out from movement of the car or do you think pressure is pushing it up somehow to the lid?

Thanks very much!

Answer
Hi Dave,

I think it's possible you may be filling the reservoir too much. I'm not sure on those older ones but I'd assume those master cylinders have a max capacity like any other reservoir.

I'm guessing that when the fluid warms up from being used, it is expanding and a few drops are making it out of the top, even though it is closed tight.

I'd keep about a 1/4 of an inch air space at the top of the master cylinder when filling it to allow for expansion.

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Thanks for the question, I hope this information was helpful to you.
Fred
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