Master Cylinder cap leak
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Tuned
Joined: Oct 2003
Posts: 390
Likes: 2
Master Cylinder cap leak
Last week my 1979 f150 master cylinder started leaking from the cap from the middle to the back. I replaced the rubber gasket in the cap and it now leaks worse, the metal holder seem really tight as far as pressure on the cap, It makes a huge mess. When I drive, it leaks more, takes paint off of metal, any suggestions ? I stopped by a brake shop, they had no ideas other than replacing the master cylinder. It sits at quit an angle, my bracket comes off the fire wall straight but where the booster bolts onto the bracket , that end of the bracket is angle back toward the fire wall slightly, making the master cylinder raised in the front and sloped down at the back of the master cylidner, is this normal for the angle ? It is a 4x4 F150 1979 with a 300 6cy.
The brake shop thought the angle postion may help cause it to leak out the back since it is not a pressure cap, What do you think ?
The brake shop thought the angle postion may help cause it to leak out the back since it is not a pressure cap, What do you think ?
Posting Guru
Joined: Sep 2008
Posts: 1,123
Likes: 4
From: Baltimore
Corrosion in the metal cap? Deformed cap? My old '75 F-100 had a problem where if the cap wasn't on a 'certain' way it would leak...And I might add this,...The master cylender is pressurised. (Take off the cover and jam on the brakes.) The booster adds an easy pedal through vacuum. The piston that sends the fluid to the brakes pressurises the fluid in a closed system. (Cap closed)
Does it leak when cold? (Just starting up?) Not running? (Pressure on the pedal with engine off?) This would eliminate boil-over.
Does it leak when cold? (Just starting up?) Not running? (Pressure on the pedal with engine off?) This would eliminate boil-over.
Postmaster
Joined: Oct 2005
Posts: 3,034
Likes: 1
From: NJ
I would check to see if your fluid is boiling over as well. At first I was going to suggest a new rubber gasket. That was what fixed my problem, but I see you did that. I don't think the angle of the m/c is causing your problem. I've seen quite a few vehicles that have it at an angle and never seen a problem come from that. If you verify that the fluid is not boiling over maybe try a new cap. Maybe it is not sealing the gasket well for some reason. It isn't overfilled is it? Even if it was the gasket should seal it though.
