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'69 1800 Plugged Brake Line

No brake fluid was getting to my rear Girling drum brakes. I took the brake valves off and cleaned them out; reinstalled and brake fluid dripped from them. I then reconnected the rubber lines that go to a connector at the top of the rear axle that turns into steel lines that run to the brakes. I opened the bleeder valves.

No amount of pumping could get the fluid to come out the bleeder valve. So, I borrowed a bleeder kit. I got one hell of a suction going. I got about three drops of very dirty old brake fluid out. I was pretty tired/dirty/fed up and should have stopped at this point. So, I decided to give the brake pedal one last pump before putting it all back together and away for the winter. While pumping, I noticed a fine mist around the master cylinder. As I was working alone, I could not verify exactly where it was coming out.

So, did I blow a gasket somewhere around the master cylinder and how should I fix this? And any idea about the back brake lines? I have a small compressor for inflating car tires. I was thinking unhooking the rubber line at the valve, opening the bleeder and seeing if I could blow some air through the lines. I believe them to be blocked. Is this an effective way of clearing the blockage, or should I just replace the lines?

Taking the rubber lines off is not easy. I do not think they have ever been off before. Tips about unfreezing threaded lines or bleeder valves would also be most welcome.
David Davidson

David says: What you have is hoses that are rotted and swollen shut on the inside. An extreme case, I'd like to add. You need new brake hoses!

What we see more often from hoses is a lesser blockage that acts like a check valve (one way valve). The master can, with pressure, push the brake fluid through the hoses to cylinders or caliper pistons, but there is nothing to generate force to move it back through the restriction. If this is suspected, try moving the piston back in after opening the bleeder screw.

The fine mist, seen while pumping the brakes trying to get fluid through the blockage, sounds like a small leak. It could be a pinhole in a steel tube, or a fitting not having adequate torque for sealing, or a poor flare on the tube (not made right, cracked, etc.).

Your concerns with disassembly of the fittings to the hoses due to rust causes me great concern with your hard brake lines in general. They are thirty years old; likely it would be wisest to replace them all. We've seen brake lines that were not as old as yours appear to be very good in the places they could be inspected. They did, however, have leaks from small rust holes in the areas where the steel line is clamped to the body and the front crossmember.

An overhaul of the remaining hydraulics should also be completed at this time. New or rebuilt master cylinder, calipers, wheel cylinders and the valve for the brake warning switch would make it complete. Then, with annual changing of fluid to remove moisture, you should have brakes you can have confidence in for several years.

If penetrent does not help with rusted bleeder screws, we heat them with a torch. To prevent problems with bleeder screws: remove all rust, clean thoroughly and coat the threads with antiseize compound.

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