Another Master Cyl question
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From: Michigan
Another Master Cyl question
Hi
I have a 56 F100 that has a Volare frt susp, approx 1972 Ford truck 9 inch and a M/C and booster from a 79 LTD11.
You can bleed all the brakes and get a nice steady stream of fluid.
The problem is the front section of the master cylinder is leaking when the brakes are applied. Took the cover off and the front section (rear brakes) shoot a stream of fluid about an inch high also you can clean the fluid off of the outside of the cylinder (with the fluid level approx a 1/4 inch from the top) and after a few days of setting it will wick up the sides and past the gasket dripping fluid on my now not so nicely painted steering gear.
I bought the truck with this brake system installed and just noticed the outside of the M/C damp, so while rebuilding the truck I bought and installed a new M/C. Now after driving it for the summer this thing is really starting to throw fluid.
Any ideas
Chuck
I have a 56 F100 that has a Volare frt susp, approx 1972 Ford truck 9 inch and a M/C and booster from a 79 LTD11.
You can bleed all the brakes and get a nice steady stream of fluid.
The problem is the front section of the master cylinder is leaking when the brakes are applied. Took the cover off and the front section (rear brakes) shoot a stream of fluid about an inch high also you can clean the fluid off of the outside of the cylinder (with the fluid level approx a 1/4 inch from the top) and after a few days of setting it will wick up the sides and past the gasket dripping fluid on my now not so nicely painted steering gear.
I bought the truck with this brake system installed and just noticed the outside of the M/C damp, so while rebuilding the truck I bought and installed a new M/C. Now after driving it for the summer this thing is really starting to throw fluid.
Any ideas
Chuck
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Joined: May 2005
Posts: 334
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From: Airdrie Ab. Canada
I would check the gasket under the cover and make sure that it is fitting tight. The fluid squirting up on release is normal on the drum brakes.
Brake fluid does make a mess of paint though, it is a great paint remover.
Don
Brake fluid does make a mess of paint though, it is a great paint remover.
Don
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From: Michigan
All ready checked the gasket seems fine, also checked the top to see if the sealing surface was flat. It was.
The fluid is squirting in the air like the rear cylinders are blocked but you can bleed the rears with no problems so I'm guessing the wheel cylinders and rubber lines are ok.
I have taken it out on the street and did a panic stop it did seem like the left front was doing more of the work. Havent had a chance to check sense I've bled the brakes.
If you leave the top off (while the truck is parked in the garage) and cover it with a rag it will not weep out of the M/C.
It really wants to leak after you take it for a drive.
Your right brake fluid is a excellent paint remover
except I don't want the paint removed from my steering gear and frame.
Thanks
The fluid is squirting in the air like the rear cylinders are blocked but you can bleed the rears with no problems so I'm guessing the wheel cylinders and rubber lines are ok.
I have taken it out on the street and did a panic stop it did seem like the left front was doing more of the work. Havent had a chance to check sense I've bled the brakes.
If you leave the top off (while the truck is parked in the garage) and cover it with a rag it will not weep out of the M/C.
It really wants to leak after you take it for a drive.
Your right brake fluid is a excellent paint remover
except I don't want the paint removed from my steering gear and frame.Thanks
Last edited by merc546; Nov 7, 2006 at 09:58 AM.
Hotshot
Joined: Oct 2004
Posts: 15,882
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From: Durham NC
What OEM application is the MC for? Sounds to me like the MC cap is not venting, or the MC is being overfilled. Is the gasket for the MC cover one of the full cover bellows style where there is a rubber bellows that fits in each chamber? If so there should be a vent in the cover to equalize the pressure. Also check that the bellows do not have a break or hole in them. There isn't any residual valves in the rear line is there?
Are your front brakes disk or drum?
Are your front brakes disk or drum?
Last edited by AXracer; Nov 7, 2006 at 12:03 PM.
Lead Driver
Joined: Apr 2002
Posts: 8,813
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From: Littleton, New Hampshire
It has to be a faulty gasket. There's nothing else I can imagine that would cause such a leak. Some master cylinders should not be filled to capacity. A 1/4 inch from the top seems pretty high. You could probably get by filling to within a 1/2 inch. That's about where I put mine. 
Roast em' if you got 'em
Joined: Mar 2005
Posts: 22,022
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From: Rio Rancho, NM
It seems like a master cylinder will leak like this only after you get a nice fresh coat of paint on the valve covers, something to do with Murphy's Law I'm told.
I was able to replace the gaasket in the top of the MC, picked one up at the local parts house for less than $10.
Bobby
I was able to replace the gaasket in the top of the MC, picked one up at the local parts house for less than $10.
Bobby
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