Leaky master cylinder

[TXJayhawk]

1981 Brat GL, rear reservoir but not front of the master cylinder completely drains out. Master cylinder says F (assume Front brakes) under the rear reservoir and R under the front reservoir (assume rear brakes), Mechanic in December said Rear wheel cylinders were leaking and should be replaced (they put on new pads and flushed brake fluid from entire system)

Ideas? Maybe flushing caused the master to leak? I have spare NOS Master cylinder plus front caliper rebuild kits and new rear wheel cylinder. What to try first? Also recently welded some rusty bits (maybe a brake line got damaged during the welding but did use welding blankets to cover nearby areas). 

Any suggestions welcome as right now not driveable. 

 

 

[idosubaru]

If the master cylinder is leaking, replace it. 

The title says "leaky master cylinder" and then discusses front caliper rebuilds, rear cylinders leaking....

If you already know what's leaking - replace it.

[TXJayhawk]

I still need to confirm that the master is where the leak is. I guess just refill with fluid and stomp on the brakes a few times and look for fluid? I have never worked on the brakes before myself-always had a mechanic do these but trying to restore this thing on a budget. 

[idosubaru]

11 hours ago, TXJayhawk said:

I still need to confirm that the master is where the leak is. I guess just refill with fluid and stomp on the brakes a few times and look for fluid? I have never worked on the brakes before myself-always had a mechanic do these but trying to restore this thing on a budget. 

If you're draining the master cylinder - that's a sizable leak.  First step is to simply go look under the vehicle for signs of fluid leaking. 

The obvious starting point may be what the mechanic said - rear wheel cylinders.  He could have just been guessing, maybe he didn't pull the covers, I don't know - you'll want to confirm, but that's the first place to start.  

1. pull the wheels and drum cover off and look for fluid around the wheel cylinder.  Google image search or get a Brat FSM or diagram of the brakes so you know what you're looking at.  Almost any 80's rear drum brake is going to look similar conceptually speaking and give you an idea of what to look for so it doesn't have to be the exact same year or even a Brat, you just need a Subaru rear drum brake, preferrably from the 80's. 

2. Follow each brake line from each rear wheel starting at the wheel and working your way away from there. Follow each line and look for signs of rust or leakage.  A rusty line will have scaled and layered rust which the brake fluid "soaks into" and it can get weak, loose brake pressure, and not drip onto the ground

Sometimes there are real clear obvious guesses you can rule out first.  Due to age and lack of information it's hard to guess here. 

It would be best to verify exactly where the leak is coming from and not guess.  You're more than likely to get it wrong - like it looks like you were going to guess and replace the master cylinder which, at least with what I see now, doesn't seem to be leaking or the problem. 

[TXJayhawk]

Thanks for the suggestions. I have the FSM and Muir book so rear drums are doable-will start there with the wheel cylinders and then trace the brake lines.

 

[moosens]

Got a second vehicle to operate while you put this one on stands ? 
 

Probably easy for me to say gather all the parts because I can easily come up with them and others may not. But my opinion is that if you search , really search and devote appropriate time you will come up with the parts you need. Assuming you don’t need to replace the calipers and rotors. Although even those are still out there if you .....really search. 
 

To me given the age of these vehicles a thorough exchange brake components and lines are top priority. Do it all now before parts are gone for good. 
 

Re-seal / overhaul kits can be found for the calipers and drum cylinders. Lines can be made. Some 80’s front flexible lines can be worked as I recall. And yes there are master cylinders too. It’s your baby. Just do it all and be proud of it. Anything short and you’re just waiting for the next episode. 
 

Just my opinion. Good luck. 

[TXJayhawk]

Yes this is the weekend car -the commuter options are 2017 Impreza Limited, 2018 Legacy Limited and 2020 Forester Sport. Once the. Body work gets finished, a complete brake overhaul is next followed by all new front end suspension and rear bushings/shocks. One thing at a time!

She does turn 40 next year so refreshing is definitely needed to keep her running another 40. A low 107,000 original miles.

 

 

[Crazyeights]

As was said above ^^^^^ rebuild the brake system - especially ALL of the hydraulics NOW. I would park it and drive something else until all of the brake issues are taken care of. A brake fluid leak is nothing to fool with. Sooner or later you will try to stop and the pedal will suddenly go to the floor. I have had this happen in the past and it's scary! If your lucky it will only be a minor accident, could be you or someone else dies. The parts to fix this can probably still be located now, but not for much longer. Pay attention to the parking or emergency brake too. It often gets overlooked. Get used to testing it on a regular basis. It could save your butt one day.

Find an empty road or parking lot and practice stopping without using the brake pedal (downshifting and parking brake) and see how well you do. I test this method with all of my cars periodically to stay sharp.

[TXJayhawk]

Talked with my mechanic and he will do total overhaul front to back just waiting on some calipers to arrive 

[moosens]

One on the way , I can just sense it. 

[TXJayhawk]

Parts Guru! Keeping it running