Mushy Brakes?

[Chernobyl]

About two days ago, my GP's brake pedal decided it wanted to go down almost to the floor before it started braking. I popped the hood and found the reservoir cap was off, so I replaced that. It's been really humid here, so I figured that a bunch of moisture got into the fluid and I had water in there, so I bled and replaced the brake fluid.

However, it's still nice and mushy.. It's gotten a bit better, it might start braking at the midway point, but it's far from what it should be.

My only other thoughts are the caliper slides.. Could that be it?

Any other suggestions?

[FuglyGTP]

whats the procedure you are using for bleeding brakes?

[Chernobyl]

I just put it up and gravity bled it, since I don't have any vacuum gadgets.

[cleangtp]

Or you buy the Motive Power Bleeder and drain and bleed your brake system with all new fluid with no mess and 1 person for 60 bucks!

[Bio248]

youre not bleeding the brakes by using another person pumping the pedal? then youre not bleeding the brakes...

[FuglyGTP]

If you are doing this by yourself, try using a set of speed bleeder screws. Its a brake bleeding screw with a check valve in it.

Russell Speed Bleeder - Lightning Motorsports - Made with Bits of Real Lightning, so you know it's good ! AEM-ARP-Competition-Skunk2-Walbro-more

[cleangtp]

youre not bleeding the brakes by using another person pumping the pedal? then youre not bleeding the brakes...

Hate to correct you but watch and learn. Been bleeding my brakes and changing fluid by myself since this came out!



http://www.youtube.com/watch?v=d0h5bMoW-aw

[Bio248]

never seen that before. good deal.

i always use another person.

[cleangtp]

never seen that before. good deal.

i always use another person.

That's pretty nifty eh

I love this tool, I've always owned cars with black azz dirty brake fluid. Never wanted to pay anyone to do it and well bleeding the brakes the conventional way sucks donkey balls. I charge $75 bucks per vehicle to use this tool, people have no idea how easy I have it but are loving the better pedal feel and nice clear, clean brake fluid.

[SJAndrew]

I own the same thing - it's a Godsend.

[cleangtp]

Without a doubt, you can buy different caps and lines for different makes but the gm fit's a lot. Just have to make sure you fill it with clean fluid to the top so you don't run out to do the whole car. Your fluid with be black and it's just a good way not to degrade your solid brake lines.

[Chernobyl]

What else would cause the brakes to act like that, though?

[Bio248]

a leak somewhere.

[BillBoost37]

Old worn hoses that balloon when you press the pedal, leaking caliper seals etc.

[SJAndrew]

Two things cause mushy brakes:

1) Leaks
2) Compressible elements in the hydraulic circuit

As for leaks, this does not necessarily mean external leaks (although they also apply). You can have an internal leak in your master cylinder that will definitely cause mushy brakes. The easiest way to diagnose this is to stand on your brake pedal. If the pressure builds, peaks, but then slowly goes away and the pedal goes to the floor, you have a bad (leaking) master cylinder (or a hydraulic leak somewhere in your system).

#2 covers air to expanding brake lines. The flex lines near the wheels can wear out or be saturated with a foreign substance such that they lose their ability to remain rigid under pressure.

What I can say is that I hunted down air in my system for months to try and stop mushy brakes. It finally dawned on me that I was ignoring my master cylinder. I tested it and replaced it - brakes are like a rock now.

[Chernobyl]

The easiest way to diagnose this is to stand on your brake pedal. If the pressure builds, peaks, but then slowly goes away and the pedal goes to the floor, you have a bad (leaking) master cylinder (or a hydraulic leak somewhere in your system).

This is exactly what it's like. I can 'pump' the brakes to get it to stop about a third of the way down, but once I'm stopped, it slowly sinks to the floor, and I doubt it's a leak, since fluid levels have remained high, and I've never noticed any leakage in my garage.

[SJAndrew]

This is exactly what it's like. I can 'pump' the brakes to get it to stop about a third of the way down, but once I'm stopped, it slowly sinks to the floor, and I doubt it's a leak, since fluid levels have remained high, and I've never noticed any leakage in my garage.

The master cylinder can leak internally.

You don't lose fluid - the internal rings are worn and it's allowing the piston to push past what should be a sealed interface within the master cylinder itself.

There is some good information here.

[Chernobyl]

Oh, no, I had no doubts that it was an internal leak with the master cylinder, I was just saying I don't think it's bad brake lines. I inspected all of them, so I didn't think it was external.

Thanks much for the advice, saved me a lot of heartache pulling out things that were fine.

[Chernobyl]

Yeah, pulled the cylinder and replaced it, and it works great now. Thanks again.

[SJAndrew]

Glad it worked. That's the same thing that happened to me.

I kicked myself for not thinking of it sooner. I spent weeks hunting down air only to replace the MC more out of exasperation than anything else. The first test drive was a night and day difference - the brakes bit like they're supposed to.