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chrisp
New User
Feb 15, 2009, 2:35 PM
Post #1 of 10
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Brakes are spongy
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98 Jimmy SLE, 3.0 6 cyclinder, 128K
Three weeks ago I had the rear brakes overhauled (new calipers, linings); today I have a constant warning lamp (brake) and spongy brake peddle. No lost of brake fluid in reservoir, no leaks on wheels. What would cause this problem? Could the problem be master cyliner be bad or brake differential module? How can I tell?
Thanks,
Chris
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dmac0923
Enthusiast
Feb 15, 2009, 2:44 PM
Post #2 of 10
(4319 views)
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Re: Brakes are spongy
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the brake light on the dash is most commonly triggered by low fluid level in the resevoir. the new brake fluid will be crystal clear unlike the old dirty stuff so you may have to actually pop the cover off and take a look inside to verify a level in the resevoir.
to me i think you have a small leak and or air pockets.
first thing is to double check the fluid level. then find out where the fluid is going or air is gettin in
__________________________________________________
2015 Jeep Grand Cherokee
2002 Ford Ranger
2004 Toyota Corolla
1969 Ford Mustang Mach 1
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chrisp
New User
Feb 15, 2009, 3:41 PM
Post #3 of 10
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Re: Brakes are spongy
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dmac0923,
I called myself checking the fluid level, based on your reply I checked again. It appeared to be 1/2 way between min and max so I started adding fluid, it took 4 - 6 oz before it reached the full line. I started the car and the warning light was still on, I pumped the brake peddle and it had the same spongy response. I held the peddle down with constant pressure and it "popped" slighly under my foot and the light went off and the pressure returned to the peddle. I took it for a spin and all is well! Could there had been dirt in the master cylinder or fluid causing the problem or am I looking at a potential failure down the road. No fluid leaks anywhere.
Thanks for your help.
Chris
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Loren Champlain Sr
Veteran
/ Moderator
Feb 15, 2009, 5:18 PM
Post #4 of 10
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Re: Brakes are spongy
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Chris; As dmac stated, the light will generally come on if the fluid level drops. The spongy brake pedal is indicative of air in the system. Assuming the fluid was full after the brakes were done, it (the fluid) had to go somewhere. The 'pop' you heard was probably the proportioning valve centering itself. You were probalby running on only two brakes until that point. If this has power brakes, and I'm certain that it does, unbolt the master cylinder from the power brake booster. (two nuts). You shouldn't have to disconnect the brake lines. Pull it forward enough to see if it is leaking fluid out the back of it. The fluid can leak into the booster so you won't see any outward signs of leakage.
Loren
SW Washington
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cpaine0106
User
Feb 15, 2009, 6:18 PM
Post #5 of 10
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Re: Brakes are spongy
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in addition, I've seen more than one case of calipers being installed on the wrong side of the vehicle, although fairly unlikely if you went to a reputable shop, it can't hurt to check. If installed correctly, there will be a bleeder valve near the top of each caliper. If installed on the wrong side, the bleeder valve will be near the bottom, leaving an area higher in the bore that air will be trapped in, resulting in a spongy pedal.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Feb 16, 2009, 3:40 AM
Post #6 of 10
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Re: Brakes are spongy
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All of the above and to add: It may be fine now but needs inspection. I think it's likely the proportioning valve as Loren said was off center, triggers light, and now is back and will feel better and able (subject to inspection again) to work properly. Brakes will feel like crap when it's stuck to one extreme and a shop shouldn't have released the car like that which is worrysome! After brake work the fluid should have been to full/max level not just within the range. Being able to add 6oz is a lot!
T
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chrisp
New User
Feb 16, 2009, 7:39 PM
Post #7 of 10
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Re: Brakes are spongy
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Thanks for the input; I will check out the calipers and master cylinder to verify their orientation and seal.
The repair was done by the local GMC dealership and I paid dearly for it; this 98 Jimmy has become the main ride of my youngest daughter and I wanted Delphi parts and not auto zone ( my usual fix it shop).
Again thanks for the help everyone.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Feb 17, 2009, 1:50 AM
Post #8 of 10
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Re: Brakes are spongy
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Sorry to beat on this but it needs to be understood. This sucker (generic idea of one) is a "combination" valve for brakes. It is the traffic cop if you will of the brakes and usually plain works and gets little notice. When pressure is off center - meaning back or front isn't getting an equal force from the master cylinder it slides inside, can lock out the weaker system (kinda like a turnicate) to stop the blood flow (bleeding) of a failure and triggers a red brake warning light too.
That can happen when fluid is out of balance for any reason, low, bleeding brakes on one end - like you just worked on fronts leaving backs alone etc. Some will stick off center and you need to bleed the stronger side to recenter it or you will be reduced to just one system of the dual/split braking system all cars require if sold to the USA since 1967!
Note: In replacing calipers or anytime brake bleeding will be involved the master cylinder is usually pumped up to build up pressure to bleed out brake parts at the bleeders of each wheel OR just the end you worked on. In doing so the master cyl and brake pedal probably travelled further down towards floor than it ever has in ages which can be all crusty there and ruin a recently operative master cylinder just in the course of bleeding brakes. They can fail without leaking fluid out at all or leak down the back at booster - possibly inside and unseen or in plain sight.
Note of reservoir: They need to be within range and NOT overfilled! Too full doesn't allow for expansion normal with heat - know that and keep it in range.
Other notes: Using a GM dealer for a GM vehicle of this age is no assurance that they will use GM parts (at least around me) unless YOU specify.
OE parts or higher price doesn't necessarily mean better parts! Ask each time for what the shop thinks is best for you and your budget.
*************
To add: I'd like to think that when brake work especially is done on a vehicle that it is test driven at least a little before handing it back over to the customer. Did they feel lousy when you picked up the vehicle?
T
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chrisp
New User
Feb 21, 2009, 5:40 PM
Post #9 of 10
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Re: Brakes are spongy
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Tom,
Thanks for the input. I pulled the master cylinder and did not see any evidence of a leaking seal, both the master cylinder and piston are clean. I bled the brakes starting with the rear; the front left brake had air in the line, once bled the brakes were tight again. I topped off the fluid; all is well.
I guess the air got in during the rear brake repair; the dealership said that they did a test drive and it all checked out and to their credit it did drive fine until a couple of days later. I guess it took some time for the air to work its way down to the caliper.
Again thanks for the direction.
Chris
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Feb 21, 2009, 5:59 PM
Post #10 of 10
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Re: Brakes are spongy
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OK: Relax but pay attention to it. Air didn't come from nowhere from feeling fine for a few days so something's lurking OR it's done with now - dunno?
A maybe: If fluid was left a good bit low and you may have noticed a rubber seal at master follows fluid as it normally drops with wear (no leaks allowed) which helps prevent splashing around in there. So - if it was low and the rubber wasn't snug as it was intended to be you might have just hit the brakes during a turn, bump or something and caught some air and pumped it in. It could either come back up to master if just a tad or travel on and be caught in the caliper eventually. Air anywhere in the pressure parts would feel the same so it got in there somehow and that's a maybe for how.
There's some oddities like the master itself might draw in air when you let go of brakes but these things are so rare you'd never prove it so easily.
Just keep an eye on it and if it feels spongy again gotta dig for why as that's not cool.
If it does this again hit back with the circumstances and let's take care of it post haste. It might and probably is just fine but do watch,
T
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