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Discussion Starter · #1 ·
On my commute home yesterday, my brake pedal starting engaging lower and lower. Immediately I thought slave cylinder, but my brake fluid is still full, zero lost. Looks a little gross, but that wouldn't have been anything I done yesterday (I autocross it). Anyone have any ideas? There's a weird clunk coming from the front left size of the car that started at the same time as well (not strut bearings). I only notice it when the clutch is engaged. Not sure if this is the only time I can hear it over my exhaust, or if it's the only time it happens
 

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Could be the master cylinder or BCM. Scan it with VIDA and look at the brake pressures.
 

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Discussion Starter · #3 ·
Could be the master cylinder or BCM. Scan it with VIDA and look at the brake pressures.
I'll do that tonight then. What should I be looking for?
 

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I'll do that tonight then. What should I be looking for?
Brake pressure when depressed and not depressed for left and right sides. Also if there are any BCM/antiskid codes.
 

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That is the common failure mode of the master cylinder. Imagine a piston with seals on it inside of a cylinder, when the seals fail you got no pressure.
You lose no fluid, there is no leak, and its very dangerous.

If volvo will tell you the brake pressures on each side and front/back you can easily tell. But if you have no leaks anywhere, its 9/10 certain to be the seals in the master.
 

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That is the common failure mode of the master cylinder. Imagine a piston with seals on it inside of a cylinder, when the seals fail you got no pressure.
You lose no fluid, there is no leak, and its very dangerous.

If volvo will tell you the brake pressures on each side and front/back you can easily tell. But if you have no leaks anywhere, its 9/10 certain to be the seals in the master.
You can see all of the pressures with VIDA.
 

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