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Excessive travel in brake pedal before stopping (resolved)

Help, Advice, Owners' Discussion and DIY Tutorials on Volvo XC90s. The XC90 proved to be very popular, and very good for Volvo's sales numbers, since its introduction in model year 2003 (North America).
mknoll10
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Year and Model: 2005 XC90 T2.5
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mknoll10

Excessive travel in brake pedal before stopping (resolved)

Post by mknoll10 » Mon Nov 21, 2016 9:57 am

I had this tagged to another post because I thought it could be related to a spring/shock problem, but it turned out to be unrelated. I'm reposting the brake issue here in case anyone else has a head scratcher of a brake problem and doesn't want to change the entire brake system (like I ended up doing):

My wife drives our XC90 to and from work, 10 miles, mainly 35 MPH stop and go. Two years ago she had a "braking incident" where she felt she lost braking power and was so scared I had to come and switch vehicles with her. Of course the brakes felt OK to me, maybe 80% of normal and changed rotors and pads on the front (the rear brakes/rotors were changed 10,000 miles earlier). Ever since then the brakes felt about the same, a little soft and a bit of extra travel on the pedal but always consistent and always working. Last week she had another scare when she was coming off of the highway and wasn't braking fast enough and ended up stopping hard as she approached the intersection. I've been scratching my head on this one for a few years as I can't find anything wrong other than a somewhat spongy pedal. I check the brakes every time I rotate the tires and bled them a few extra times and finally this last week I could see that the inner face of the rotor on the driver side is only worn on the bottom 2/3 and the top 1/3 is rusted and raised. I assumed the caliper was a bit sticky and opted to replace it with new rotors, stainless wrapped brake lines, and pads. It turns out that both front rotors had the same wear pattern, so I checked the rears and same issue to a lesser extent.

I replaced all 4 calipers, rotors, pads, and changed brake lines to SS wrapped flex lines, still no fix... I pulled the master cylinder and found that the front chamber (the chamber closest to the front of the vehicle) was dry, no fluid was pumping through. I hand-primed the master cylinder a few times and fluid only came out of the rear chamber, I plugged the rear with my finger and primed the MC again and suddenly the front chamber was working again??? Must have been a blockage in that chamber feeder. Very odd that bleeding the brakes did not send fluid through the front chamber. After putting it all back together I essentially did a bench bleed by loosening the brake line at the Anti-Lock Brake controller for the front and back MC chamber while the pedal was depressed until I saw fluid spurt out. Brakes are now best they've ever felt.

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