Leaking master cylinder r80

if you have a hydraulic clutch ( no transmission offered) check the slave cylinder for leaks ( some cars use the brake master cylinder as a reservoir for the hydraulic clutch)
check the brake booster to master cylinder mounting for leaks or the rear seal of the master cylinder may be faulty allowing fluid to pass to the booster chamber
check for a leak under pressure at the rear flexible rubber hose from the body on

Check the fluid in the master cylinder. If there is a leak in the brake system, one side of the master cylinder will lose its fluid. The is a proportioning valve that is part of the brake system that will shift under uneven pressure to shut off the leaking side. When this occurs it will light the brake lamp. If your master cylinder reservoir is low on one side, have the brake system checked for leaks immediately and repaired.

Lingo is o.k., but I think you may be confusing power steering with power brakes. Power steering has no master cylinder (brakes do) and no power booster (brakes do). The power steering pump is mounted on the front of engine and run by the fan belt or the serpentine belt. The p/s hoses are 2- a pressure line and a return line, and run from the pump to the steering box or to the rack and pinion steering gear.
It just sounds like you have a brake fluid leak at the master cylinder. If it is, you need a new or rebuilt brake master cylinder.
Good luck. Post back for more.

air must be entering the system somewhere, check all wheel cylnders for leaks, and check the master cylnder for leaks( some cars's master cylnders leak at the firewall and fluid runs down inside the car under the carpet)

Check for brake leaks. Make sure that the resevore is full. With the engine off pump the brakes then check for leaks. If there is no leaks then bleed the brakes start with the right rear and work clock wise around the truck. If there is no air that comes out of the lines and the fluid looks clean your master cylinder went bad and it is a easy replacement. To replace the master cylinder you'll need a 14 mm for the lines and a 15 mm for the booster. Thanks!

You will need to carefully inspect the entire brake system for leaks. Inspect the front calipers, rear wheel cylinders, all the hoses, the back of the master cylinder, and steel lines. If something looks wet or drips brake fluid it is leaking. If you haven't seen any brake fluid dripping from under the car my first thought is that the rear wheel cylinders are leaking.

If the pedal went to the floor and you didn't have to add fluid than you would more than likely have a bad master cylinder but since you are adding fluid there is a leak somewhere.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

If you don't have any leaks , then your master cylinder is toast, and will have to be replaced. Look under the truck at the inside of the wheels. If one or more of them is wet with brake fluid, it's probably a wheel cylinder leaking. If it's all dry, and no leaks anywhere else, and your master cylinder is full, then you need a master cylinder.

1. What is the Brake Fluid Level?
2. Are you losing any Brake fluid at all? Are there any puddles or noticeable wetness on the ground or on the tires/wheels? With vehicle parked, the reservoir filled (overfilled), and engine running: pump the brakes and check on the ground and back sides (inside portions) of the wheels. Look for any brake fluid leaks.
3. Leaks from Calipers usually means a leak from the caliper piston. The rubber seals will be wet.
Leaks from Drums usually means a leak from the wheel cylinder.
4. In any case of leaks from the wheels - replace the calliper OR wheel cylinder.
For caliper leaks: change the brake pads, and clean the rotors with brake cleaner.
For drum leaks: clean the drum and brake hardware with brake cleaner, and replace the shoes.
5. If no leak is detected from the wheel area's: check under the Master Cylinder for wetness indicating a possible leak.
6. If no leak can be found: you MAY have a rear seal leak in the Master Cylinder which is pumping Brake Fluid into the Brake Booster (that large disk looking thing attached to the fire wall, attached to the Master Cylinder in front).
a. Use a large drip/catch pan under the Van in the area on the Master Cylinder.
b. Disconnect the brake lines from the Master Cylinder using a flair wrench.
c. Remove the two nuts (12 or 13mm?) attaching the Master Cylinder to the Brake Booster. If you have been using a lot of fluid, and have found no leaks, here is a good possibilty that all that brake fluid has collected in the Booster; so when you detach the Master Cylinder from the Brake Booster, all that fluid will come rushing out!
7. If there is Brake Fluid inside the Brake Booster: there is no cleaning that out. Brake Fluid is very caustic to the seals inside the Booster and should be replaced.
8. Of course the Master Cylinder will also have to be replaced.
9. After replacing the Master Cylinder/Brake Booster - make sure you get all that spilled brake fluid off the engine compartment area parts! I use a brake cleaner, then mild soap and then water to rinse. Clean any Brake Fluid off Paint imediatley as it will quickly dissolves finishes and paint.
10. If no leak is detected and the Booster is clear, there may be problems with the Booster One-Way Valve. This is attached to the outside of the Booster and has a hose from an "advance" connected to it. This maybe malfunctioning where you are losing power. Replace this first before deciding to replace the whole booster (in cases of NON-LEAKS ONLY). If that did not work, there may be inner seals inside the Booster that have failed. That means a new Booster.
11. In any of the above cases: Make sure you bleed the Master Cylinder correctly and bleed the brakes (at each affected wheel) correctly. Any air in the brake lines will decrease your braking proficiency or could result in brake failure.

Let me know if this helped or if you have any additional information or questions. Feel free to contact me at FixYa.com!

that would be brake fluid leaking you have a broken line..

The warning light is triggered by a loss of hydraulic (brake fluid) pressure in the system. look under the car at the inside of all 4 wheels for discoloration from leaking fluid. Inspect the rubber brake hoses. Inspect the area under the master cylinder on the firewall as well. Lastly, a master cylinder can have a leak (blown seal) internally that would not be detectable externally. A dead giveaway for this is brake fluid that is very dark or black.