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By easyissy - 15 Years Ago
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My master cylinder cap was leaking on my '58 Fairlane so I purchased a new one. I refilled the master cylinder and installed the new cap. The cap has two holes in it (I think to vent out the air) but when I apply the brakes, fluid shoots out of the holes. Did I put too much fluid in?
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By oldcarmark - 15 Years Ago
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Did you bench bleed the master before installing?Sounds like air in the cylinder.
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By easyissy - 15 Years Ago
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The master cylinder was never removed, just the cap. Would air in the master cylinder cause it to spit out brake fluid from the cap?
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By Ol'ford nut - 15 Years Ago
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I hate to ask this but is there a rubber seal under the cap?
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By easyissy - 15 Years Ago
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No, just the gasket for the cap itself. Should there be a rubber diaphram of some sort underneath? If so, where can I buy one??? or can I make one???
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By easyissy - 15 Years Ago
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In the manual it does'nt mention any diaphram below the cap. 
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By oldcarmark - 15 Years Ago
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Only the gasket as shown is used.I am not sure why you are having trouble.Maybe someone else will.I didnt read your original post properly.
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By easyissy - 15 Years Ago
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After reading the manual I think I may have put too much fluid in. The manual states "fill the master cylinder up to 1/2" below the top of the fill opening" Could this be it?
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By paul2748 - 15 Years Ago
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easyissy (9/29/2010)
After reading the manual I think I may have put too much fluid in. The manual states "fill the master cylinder up to 1/2" below the top of the fill opening" Could this be it?
I would try that. The stock master cylinders that I had on my 54 and 56 TBird did not have any vent holes in the cap.
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By oldcarmark - 15 Years Ago
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Hi Paul.You are correct about no vents.I just remembered the one that was on mine originally was a solid cap.If you look at Ebay item # 190437936565 you can see its solid.Even the replacement dual master on mine now has the solid steel clip-on cap with a rubber seal under it and no vents.
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By easyissy - 15 Years Ago
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Here's the one I bought from Mac's Antique: 
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By MoonShadow - 15 Years Ago
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If not overfull could one of the rubber cups in the cylinder be letting pressure back into the fluid area? Chuck in NH
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By easyissy - 15 Years Ago
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I can't figure this thing out. I have tried to bleed the brakes with no luck. Could my master cylinder be bad?
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By oldcarmark - 15 Years Ago
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What was the original reason for changing the cap?
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By easyissy - 15 Years Ago
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Well, the original cap was leaking so when I bled the brakes it would only last a few days then I would get a lot of air in the system and I would have to rebleed. Now that I have a new cap it does'nt leak but I can't seem to get any 'feel' on the brake pedal, it just goes straight to the floor. The master cylinder is full, I tried bleeding the brakes but the pedal still goes to the floor and the master cylinder is still full. What could it be other than the master cylinder itself? Before it would go to the floor but then I would keep pumping until it 'catches' now I don't get anything when I press the pedal.
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By MoonShadow - 15 Years Ago
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You may have to remove the master cylinder and bench bleed it first. Sounds like pressure is getting past your seals in the master cylinder anyway. Probably time to put in a kit. If pressure gets by the seals it could cause brake fluid to back up into the fill area and leak out. See attached picture. Chuck in NH 
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By oldcarmark - 15 Years Ago
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I think you need either at least a kit but if it was me I would be buying a new master cylinder.When (or if) you replace it bench bleed it first before installing using a length of brake line and bend it so it is under fluid in the resovoir and pump it to recurculate fluid back into resovoir until there are no air bubbles.It works much better than trying to push air out through the whole system.Macs has the new master for $90.00(with cap).
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By easyissy - 15 Years Ago
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I think a new master cylinder is the route I'm gonna go just to be safe. Thanks for all the help. I'll keep you posted.
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By easyissy - 15 Years Ago
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I put in the new master cylinder and the brakes work great. The only thing is the top (2) holes in the cylinder did'nt match my original location but I guess that's fine. I'll just use some sheet metal screws to secure the top (2) holes.
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