Brake Fluid "Disappearing" 57 With Power Brakes

[TJShea]

Another stumper for me, which actually is not very hard. Today when starting the car, the brake pedal went to the floor, and there was virtually no, if any, working of the brake shoes to stop the car. I checked the master cylinder and it was virtually empty. I had the brake booster replaced two months ago. The worksheet shows the technician bled the brakes. I did think they were a bit spongy yesterday. They failed today, luckily in the garage. I have paperwork that indicates all of the brake cylinders were replaced about 2000 miles (long before I acquired the car). I filled up the master cylinder with brake fluid, started the car, and pumped the brakes about 6 times, and they firmed right up. I tried a couple little test stops and the brakes worked as they should. I am going to get it to a repair place to look the entire system over, but I was curious just where could the brake fluid go? I do not see anything around the wheels, in the engine compartment, or under the car that looks like brake fluid dripping. Any thoughts?

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[Robert Evans]

Another stumper for me, which actually is not very hard. Today when starting the car, the brake pedal went to the floor, and there was virtually no, if any, working of the brake shoes to stop the car. I checked the master cylinder and it was virtually empty. I had the brake booster replaced two months ago. The worksheet shows the technician bled the brakes. I did think they were a bit spongy yesterday. They failed today, luckily in the garage. I have paperwork that indicates all of the brake cylinders were replaced about 2000 miles (long before I acquired the car). I filled up the master cylinder with brake fluid, started the car, and pumped the brakes about 6 times, and they firmed right up. I tried a couple little test stops and the brakes worked as they should. I am going to get it to a repair place to look the entire system over, but I was curious just where could the brake fluid go? I do not see anything around the wheels, in the engine compartment, or under the car that looks like brake fluid dripping. Any thoughts?

Hi. Take a look inside the car where the brake pedal attaches to the brake booster. You may find its damp with brake fluid.

 

[64ZCODE]

Check for fluid in the booster, most likely your master cylinder is leaking into the booster. If that's the case, you should be able to save the booster by suctioning the fluid out, rinsing it with brake cleaner, and letting it air dry. Then replace or rebuild the master cylinder of course.

 

[jack-in-sac]

Just to be on the safe side; see if the master cylinder is leaking out the rear where actuator rod inserts. If it leaks there, you lose fluid and never see where it has gone unless you check to see if it is wet down the inside of the firewall and under the sound deadener and carpet in the cockpit. Additionally a wheel cylinder can weep over time and check each wheel cylinder.

 

[doug7740]

Another stumper for me, which actually is not very hard. Today when starting the car, the brake pedal went to the floor, and there was virtually no, if any, working of the brake shoes to stop the car. I checked the master cylinder and it was virtually empty. I had the brake booster replaced two months ago. The worksheet shows the technician bled the brakes. I did think they were a bit spongy yesterday. They failed today, luckily in the garage. I have paperwork that indicates all of the brake cylinders were replaced about 2000 miles (long before I acquired the car). I filled up the master cylinder with brake fluid, started the car, and pumped the brakes about 6 times, and they firmed right up. I tried a couple little test stops and the brakes worked as they should. I am going to get it to a repair place to look the entire system over, but I was curious just where could the brake fluid go? I do not see anything around the wheels, in the engine compartment, or under the car that looks like brake fluid dripping. Any thoughts?

Since your master cylinder was empty and you are sure that there are no external brake fluid leaks at the brake lines, brake hoses or at any of the wheel cylinders, then there are only two other places two look; the master cylinder and the power brake booster.

As Robert Evens and jack-in-sac said, check inside the car where the brake pedal push rod connects to the master cylinder. If fluid is leaking in this area the carpet and padding will be wet with brake fluid and the master cylinder will have to be replaced.

Since your brake booster is mounted on the left inner fender and not mounted on the fire wall with the master cylinder, if you find brake fluid in the brake booster vacuum hose then your brake booster is defective and not the master cylinder as 64ZCODE indicated.

doug7740
1955 Thunderbird Blue

 

[TJShea]

Thank you all for the info. The booster is new and was put in just a few weeks ago. Hopefully, that is not it, but it seems logical as the previous owner did not have this problem. Anyway, I will do the checks and see what i can find. I think that I will also have someone who is significantly more qualified than I am check the whole system. Can't have a brake issue. If it is the booster, that would be disappointing. I thought if the fluid is being pulled into the exhaust manifold I should see some smoke? I have not seen any. So, I think the whole system needs a close look. Thanks again for the info.

 

[64ZCODE]

Try disconnecting the vacuum port at the booster and look down inside the booster with a flashlight. Likely you'll see a pool of brake fluid there if you're not seeing leakage anywhere else (wheel cylinders, carpet under brake pedal, etc.). Not the fault of the booster. BTW no way for brake fluid to get pulled into the exhaust manifold.

 

[curtc]

The brake booster check valve on mine was bad. This allowed fluid to be drawn into vacuum port on carburetor, hence light white smoke from exhaust. I put on a rebuilt brake booster and check valve. All is well now.