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I was driving my 1997 Chevy Suburban the other day and when I pulled up to a stop sign all of the sudden my brakes felt super spongy, like the system totally lost pressure. Before that they had worked totally fine. I checked the fluid and the level was fine, and I couldn't spot any leaks. We did hit a large bump when I was pulling into a parking lot, and I thought maybe something would have dislodged one of the brake lines or something but everything seems fine. When I pump the brakes a bunch, they will kind of hold for a few seconds, but then it slips again. The e-brake works fine to stop the car, but that's not exactly a long term situation.

What's going on and what do I need to do?

Pᴀᴜʟsᴛᴇʀ2
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Wayne Werner
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2 Answers2

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Another possibility is that you broke a seal in your master cylinder. The symptom you're describing of being able to build up pressure but then lose it after a few seconds very much sounds like that.

Basically what happens is there's a seal between the lines and the reservoir, and if that seal breaks then fluid can push past it back into the reservoir, thus reducing the pressure in the lines and the pressure you feel at the pedal.

To fix this, you'd need to rebuild or more likely replace your master cylinder.

Ceshion
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I actually found the problem myself, surprisingly my first Google search turned up the answer.

Basically what happens is that you were probably pressing the brakes when you hit that pothole, and with an impact that severe, your ABS/pressure assist system gets confused and thinks that you need way less braking pressure.

The way to solve the problem is to kind of "reset" the system. Find a dirt/gravel road/parking lot somewhere, pick up some speed and then slam your foot down on the brakes. This will engage your ABS system (if you've never felt it before, the brake pedal will vibrate and the brakes may sound like they're shuddering/grinding as they rapidly engage and release to keep your wheels from locking up - this is normal!). You should notice the brakes start to stiffen up after a couple of non-slides. Depending on a variety of circumstances, after anywhere from 2-10 times of engaging the ABS and the system will figure out how much pressure it really should be applying to the brakes.

Wayne Werner
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