Spongy brakes

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Spongy brakes

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Spongy brakes - 11/28/2007 3:44:43 PM

msherman01

Posts: 20
Joined: 1/29/2005
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I changed my front break pads today. Accidently I screwed up and pressed the brake pedel when my left calipers was off the roter. In turn, my left brake piston came most of the way out, being held only by the rubber bladder. I aligned the piston best I could, pressed it back into place, and finished my brake pad replacement. I've changed my pads before and never had to bleed the brakes, but this time I had spongy brakes so I bled the system. The brake fluid resevour is full, I still have spongy brakes! There is no sign of brake fluid leakage. Could I have damaged the calipers or piston? Is there an "o" ring on the piston that I could have accidently cut? I don't think they sell rebuild kits for this, do they?

Post #: 1

RE: Spongy brakes - 11/28/2007 10:13:58 PM

snanceki

Posts: 2396
Joined: 12/11/2004
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If the piston came fully out except being held by the "bladder" (robber boot) then air has likely got in the system.
Unless you did something terrible in getting the piston back in (if the boot was in place dirt ingress would be unlikely BUT STILL POSSIBLE.
It is unlikely that you have not damaged anything..... BUT you are a little wiser.
Did any fluid spill? I hope not.
Is there any expelled fluid on/in/around the caliper now?

Guess you just need to bleed the brakes BUT with ABS /EPS etc this isn't as straightforward as it seems. Ideally you need a pressure bleed kit which basically forces fluid from the resevoir into the system otherwise you end up with no improvement after bleeding "normally".

Safety Warning!! Brakes are essential SAFETY equipment. Are you sure you are competent to be working on this system?

Good luck.

Stuart

(in reply to msherman01)

Post #: 2

RE: Spongy brakes - 11/29/2007 7:06:03 AM

msherman01

Posts: 20
Joined: 1/29/2005
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Thank you; no fluid escaped, however I did see some very small air/fluid bubbles as I was pressing the piston back in. No fluid is escaping in the in or around the caliper. No drips anywhere in the brake system that I see. If I would like to bleed this system using the pressure bleed kit, I guess I could buy one locally. Is it straight forward on how to use it, or do you have some tips?

(in reply to snanceki)

Post #: 3

RE: Spongy brakes - 11/29/2007 8:49:39 AM

lswanson

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Joined: 11/29/2007
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I'm not sure if they sell a rebuild kits for something such as that. I know I haven't seem them.

(in reply to msherman01)

Post #: 4

RE: Spongy brakes - 11/30/2007 6:43:37 AM

msherman01

Posts: 20
Joined: 1/29/2005
Status: offline

With all this going on, I let my break resevour run dry. Now I'm trying to find a master break cylinder bench bleed kit. I've got one from another make, but it doesn't fit. I'm planning on bench bleeding this while on the car. I'm sure my breaks are spongy from air in the m.b.c. I've bled all the lines three times and I'm still feeling a semi soft peddel (When I'm pushing hard on the breaks, the pedel very slowly goes to the floor). My dealer doesn't sell this bleed kit. Any Idia where I can get one? Would a pressure bleed kit do the job. How much and where to buy?

(in reply to lswanson)

Post #: 5

RE: Spongy brakes - 11/30/2007 8:55:49 PM

snanceki

Posts: 2396
Joined: 12/11/2004
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Quote..."the pedel very slowly goes to the floor".

Could be air BUT I suspect more likely a seal leak.The pedal would be spongy with air but not move slowly to the floor.

If no leak at calipers must be in the master cylinder.

However IF this only occurred after you changed the pads a "sudden" leak is unlikely (unless you damaged the caliper piston when you replaced it)

On the other hand it could be that you have fitted new pads (most likely a non Genuine MB part), and the rust ridge on the rotors is preventing the pads from coming down square/or completely onto the rotor.

Stuart

(in reply to msherman01)

Post #: 6

RE: Spongy brakes - 11/30/2007 9:06:10 PM

BlueSilver

Posts: 899
Joined: 2/24/2006
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Something is wrong. It's simply not that difficult to bleed the brakes, and I think you are doing it properly. I mean if you ran two bottles of fluid through the system, it should be working like a new car. I'm beginning to question the integrity of the brake parts.

I know that you have already checked for leaks etc. Did you know that the rubber brake hoses, running from the wheel well to the brake caliper, can go bad without leaking. They can lose their ability to hold pressure and actually "inflate out" or expand enough to absorb about two stokes of the master cylinder. It happens when the inside of the rubber brake line deteriorates from age or improper fluid. Blue

(in reply to msherman01)

Post #: 7

RE: Spongy brakes - 11/30/2007 9:49:06 PM

snanceki

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Joined: 12/11/2004
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Good point Bluesilver....but why the problem immediately after replacing the pads?
Stuart

(in reply to BlueSilver)

Post #: 8

RE: Spongy brakes - 12/1/2007 6:41:53 AM

msherman01

Posts: 20
Joined: 1/29/2005
Status: offline

I'm driving this car now. (1998 E320 Wagon) I still feel the pedel very slowley go to the floor if I'm stopped and hold pressure on it. The car brakes well, and the abs works fine. I will continue to drive this car for a while and see; Then I may bleed all the lines again and look very close at all the brake lines and check for any signs of ballooning or deterioration. I always look at the lines for wear, and didn't notice any, but I'll look very close this next time. By the way, the brake pads I used were "Akebono".

(in reply to snanceki)

Post #: 9