Brake Emergency

Check the rear wheels, at the rear of the plate, inspect it from under the car, look for oily residue, and or splatter on your wheels.
Check your rubber hoses they can crack and leak, then burst.
Master Cylinders can leak out the seal and in to the booster so if you don't have any leaks showing on the hoses or rear wheel cylinders then
Your MC is suspect.

The sensor for the fluid pressure is on the MC on early rabbits.

Fluid level should be even with the top of the master cylinders filter about 1/2 way up.
from the outside it looks full.

Hissing is usually a vacuum line, and the hard line from the Booster to the Throttle body is suspect for failure of the brakes.

nmoussal said:

My 82 rabbit's brakes are doing some abnormal things:

Brake light turns on when I brake, and recently the light stays on indefinitely regardless of braking.

Click to expand...

The light comes on because your rear brakes have failed on one side. The proportional valve, that thing on the fender where the two lines coming out of the master cylinder go. That has a switch on the top that is sensing that one side of the brakes is not as well pressured as the other. Thus Light on continually.

You need to do what Briano suggests. Crawl under the car and look for wet oily rear brakes. Or a line of brake fluid coming down from the drums. Tear into them and clean them up or replace the pads. Likely they will be saturated by now. One of the reasons your stopping distance is so great, only the front discs are doing any good.

Repair the E brake cables too. There is no good reason to leave your vehicle in that condition. It saves on engine problems and transmissions problems to have that brake working. If you lived on the hill I do your car would creep slowly down hill unless you have a good E brake engaged. Compression alone won't do.

That hissing you hear is likely the vacuum coming out of the booster. If you can pull a vacuum on the line going to the booster and have it hold then maybe you have a cracked hardline from the booster to the pump on the engine. Maybe a check valve gone bad?

Take a look at the rear brakes, both sides and see what is going on with the cylinders, the pistons, the mechanism and the condition of the shoes in general. To get the drum off you need to take the wheel off, line up one of the holes from the studs on the self adjust mechanism, a small wedge of metal near the back and lift it up with a thin screw driver. That will allow the shoes to come away from the drums and then you can slide them right off. IF you don't bump the wedge up you will fight getting the drums off as they will likely catch a lip of rust on the outside edge.

Got a Bentley manual? Library might have what you want, the exploded diagram is good for replacing the springs back in their original position. I use a pair of vise grips to get a part of the spring arm and pull it to where it needs to go.

Best of luck, Keep us up to date.

master cylinders can fail the seal on the Push Rod seal. It will leak either out of the bottom of the m/c at the booster connection or leak into the booster itself.
I have had this happen.

Removing the mc isn't that hard but it does take care, that is you loosen the nuts off the brake lines, and then loosen the mc off the booster by turning the nuts equally at the same time, that is 5 turns on the left and then 5 turns on the right, the same when you return them.

You may have to take a rag into the hole of the booster and wipe out excessive fluid if it has collected in to the booster.
Check the Vacuum line for the whole length for cracks from the booster to the intake valve.

Since you live in a hilly region, I would hope there isn't a ton of hills between you and your mechanic.

The mc has a o-ring on the neck that inserts itself into the mc to seal it.

Not all grommets are the same.

I have found over the years that some react to the type of fluid that you use and can get soft and leak as the fluid can deteriorate the
rubbers. I have found that not all brake fluid is the same. Years ago I rebuilt all the hydraulic parts of my systems (clutch and brake) with new seals, (this was on a MG) and used regular DOT3 Wagner brake fluid. In about 4 days of driving I lost my brakes and Clutch, as it ate all the seals. While IIRC the kits for the MC and Clutch were only about 20 bucks once I found the seals had weakened I talked with the Dealership of British Leyland, who said that the kits I were buying were "Natural" rubber and that Wagner would eat the seals. I switched to Castrol GT/LMA fluid and never had that issue again. I also stayed away from Wagner fluids or Generic Dot3 fluid.

Now-a-days I use only Synthetic on a new to me car since I have to flush all the systems anyway and don't have an issue either...