Master cylinder

[ddesai74]

Brake fluid is leaking for the master cylinder on my 95 aurora. Has anyone changed this? The leak is from the thick metal that connects to the big black cylinder. Do I need to replace the entire assembly? Is there a pressure issue I should be aware of?

[winrock]

Simple fic, mine was leaking at eating the paint on the booster(big black cylinder). Master cylinder from napa 60 bucks or so, simple to install, bleeding instructions came with it.

[ugsrich]

Both my father and I had the same problem on our 95’s. His leaked at about 55K and mine at about 80K. It’s relatively easy to replace. I recommend obtaining the correct flare-nut wrench(s) for the hydraulic line connections at the Master Cylinder (MC).

You need to remove the two brake lines that connect to the MC. Do this very carefully and avoid jiggling the tubes so as not to lose the brake fluid in the lines. I then covered the tubes with a clean plastic sandwich bag (one on each) and secured it with a rubber band to avoid leakage. There’s also a large rubber tube which does the recirculation of the brake fluid during an activation of the ABS that will need to be removed from the reservoir. Also you need to remove the electrical connection for the fluid-low level sensor. As I recall the big rubber tube was the most difficult part for me and as I recall caused the spillage of some brake fluid (I did put some rags below the MC prior to disconnecting). Once all that’s done you can unbolt the MC from the vacuum assist housing by removing the two bolts that secure it.

I had already purchased a new MC from AutoZone for about $75. Included with it was the MC, a new reservoir, instructions and a bench-bleeding kit. You MUST bleed the MC completely and properly prior to reconnecting the lines. The instructions will tell you to bleed them at your work bench (thus the phrase “bench bleed”). Frankly, I found this unnecessary. I installed the new MC filled it with DOT-3 fluid as stated in the instructions, employed my youthful offspring (a little indentured servitude) and did the MC bench-bleed under the hood with junior pumping the brake pedal (it is NOT necessary to have the vehicle running). Once the MC is bled you can reconnect the brake lines. If you were careful and did not jiggle them the small amount of air that may be in the line will work its way out into the MC. If however the brake lines drained at all you may need to bleed the system (that will be a slightly more tedious process so be careful when your working with the lines.) Finally make sure all connection are properly made, electrical, recirculation, and brake lines. Wipe area clean. And you should be good to go.

Estimated time: 2 hours.

This writing represents my best recollection of a repair that was fairly easy to conduct given strong skills as an amateur mechanic and my careful attention to detail. I CAN NOT guarantee your success. If you have doubts about your skills DO NOT risk your personal safety, or that of others by attempting this work yourself. Also, brake fluid and automobile paint are a BAD combination. DO NOT get brake fluid on the automobile’s finish.

[aurora199540]

i also need to replace the master cylinder on my '95..i'm just curious if anyone has successfully changed the master cylinder WITHOUT needing to bleed ALL four wheels as described by ugsrich ?? i always thought after the MC was disconnected,this would allow air into the entire system ?? also any other input in-regards to bleeding the master cylinder while on the car,rather then bench bleeding ??

[BNaylor]

Originally Posted by aurora199540

i also need to replace the master cylinder on my '95..i'm just curious if anyone has successfully changed the master cylinder WITHOUT needing to bleed ALL four wheels as described by ugsrich ?? i always thought after the MC was disconnected,this would allow air into the entire system ?? also any other input in-regards to bleeding the master cylinder while on the car,rather then bench bleeding ??

Sorry but please check the date and do not resurrect old threads. It is better to start a new thread and address your issue or question. Thread closed.


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