When i'm sitting at a stop light, my brake pedal will get softer and softer until it's finally to the floor. I always service the brakes since i race the car and so i know for sure that it's not air in the lines. Once you lift off the pedal and push it again then its firm again and will repeat the problem... anyone else experience this and if you did, what'd you do to fix it?
maybe you need stainless steel lines, i dunno seems if the pressure is depleting from that maybe your lines are expanding and contracting...that would be my clueless guess
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Your Brake master cylinder is dead - replace it as its seals are probably shot, which explains why you lose pressure on the brakes when you apply them.
Do a search on brake master cylinder - you'll see their problem is the same as yours... good luck!
I always thought that was something normal. If you pump the brakes while at a stop it will firm. Then hold down the brakes and it will slowly decrease in pressure.....if I'm not mistaken that's how you make sure your brake booster is working.
Well it could either be the master cylinder going out (most likely), but if for some reason not you may just have air in the line, if you're lucky. The reason I say this is because liquid cannot compress, but air can. If you press down on your brake pedal and it feels "spongy" it means there may be air in the line that is compressing causing the brake pedal to reach the floor. I can't say for sure because I don't know exactly how it feels but does it feel the same way all the way down, and it does reach the floor?
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Does this mainly happen on short trips as well as long ones? When my brake master cylinder went bad, the pedal would only sink when I had bee driving in the city (stop and go traffic) for awhile. It never was an issue on the highway. I think as the fluid heats up, the viscosity goes down and the fluid can leak past the seals in the master cylinder more easily. As a result, driving conditions that required lots of braking were when the problem was most noticable.
I'd say there is a 90% chance your MC is bad . . . this is a common part to replace on 4th gens (almost as common as the clutch master cylinder). A remanufactured unit will run around $60 from the parts store if I remember correctly. The installation in simple if you have worked with brake lines before, and should take less than an hour.
I just asked this question a couple weeks ago my dads lude (red 1 in sig) had this exact same problem. All it is, is the master cylinder, its dead. Replace it and it will be perfect.
if you change out the brake lines to s/s you will need to rebleed the entire brake system. Changing out the lines are fairly simple. Tad bit messy. But if you are going to do the lines, i would check the brake master cylinder as well, since if you change that you will also need to bleed the system.
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how hard is it to work with brake lines? do you have to rebleed all 4 calipers?
I did not have to rebleed my system, however I believe the Helms recomeneds it.
If you have never worked with brake fittings before, go buy a set of Flare Nut Wrenches. Brake fittings are soft metal and will be easily rounded off by standard open-end wrenches. Flare nut wrenches grip the fittings on more sides and are less likely to round them off. You can pick up a set at any autoparts store for a few bucks. Take your time and work slowly. The last thing you want to do is cross thread a fitting into your new MC. . . you will never get it to stop leaking.
The worst part about brake work is that you get fluid on your fingers, and then you can't grip fittings to start threading them into the MC. Also, the fluid kinda stings, especially if you have any small cuts on your hands. Latex gloves would be nice.
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