Zero (0) Brake Pedal after Brake Servicing on my '04 WRX - Subaru WRX Forum
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post #1 of 7 Old 04-25-2014, 01:03 PM Thread Starter
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Zero (0) Brake Pedal after Brake Servicing on my '04 WRX

Following a routine Spring brake servicing, there is NO brake pedal pressure at all. It just sinks to the floor when depressed. Now I'm depressed. Ha ha.

Investigation showed that the master cylinder just stopped pushing brake fluid when pressing the brake pedal, which is unexpected and not good.

Can the master cylinder piston shaft somehow get disconnected from the piston for any reason?



Summer 2013 we upgraded the fluid to Motul 600, but that's the only thing done to the brake plumbing since the Rex was acquired in Mar 2013.


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post #2 of 7 Old 04-25-2014, 02:02 PM
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LW_Black4,

If you serviced the brakes I would check and make sure you didnt crack/tear a brake line, thats the only time i have seen a brake system fail entirely after a service is when the tech let the caliper hang and the butyl hose ripped a bit. In that case the master cylinder emptied itself out the cracked line.

If your master cylinder is holding onto the fluid but not compressing it I would check the rod that connects from the brake pedal to the cylinder, it would be rare to have that rod dissconnect from the master cylinder.

Worst case its a new master cylinder, not a crazy expensive part but its alot of plumbing and kinda a pain in the A$$.

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post #3 of 7 Old 04-25-2014, 03:30 PM Thread Starter
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Thanks Jason,

We see no brake fluid on the garage floor, so it's not from a leak. It just sounds like the actuator rod from the pedal doesn't press against the m/c piston anymore.

Ordered an new master cylinder, which is apparently 170 $CAN.

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post #4 of 7 Old 04-25-2014, 04:16 PM
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So roughly $30.00 American.
Haha, jk
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post #5 of 7 Old 04-27-2014, 09:20 PM Thread Starter
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Pedal actuator port had some decay. No pedal action would change it, and my mechanic tried bleeding and even drawing the fluid from the lines. The master cylinder just wasn't pushing any fluid at all.

We started to suspect a mechanical linkage connection, and this is what we found when the master cylinder was changed.


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post #6 of 7 Old 04-27-2014, 09:25 PM Thread Starter
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The master had disgustingly dirty fluid, with a substantial amounts of particulate matter in in. Without fully dismantling the unit the mechanic only suspected a ripped seal but it also looked like a plugged transfer port not allowing fluid to refill the ports in the piston. Either way he said the repair is the same. Master cylinder replacement, as rebuilding is not economically feasible when a replacemant is only 165 $CAD

New master cylinder bleed and installed, full system flush and all is good in the world. Delighted to find the issue in the shop, rather than at speed. Drives like new now.

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post #7 of 7 Old 04-28-2014, 10:56 AM
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Hope no fluid got back into the brake booster!
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