My Brakes Suck!

[boatboy]

The brakes in my 96 Deville DO NOT work very well. The pedal has always felt kind of spongy, ever since I owned it (purchased ~ 90K miles). The car has 150K miles on it. I do all my own work on the car. I changed the rear pads and rotors at 110K then the front pads and rotors at 115K miles. At that point I decided to use cross drilled/slotted rotors and ceramic brake pads (FRONT ONLY). I have bled and flushed and bled and bled the brakes many, many times. I have followed the procedure in the manual for bleeding. LF, RF, LR, RR. I have had a helper with the bleeding process, I have even used a pressure bleeder. I just cannot get a firm pedal.

Heres what happens when I try to brake the car hard. The car stops but its not exactly like the ABS has to even pulse. Heck, my body weight isn’t even thrown against the seat belt. I can’t even go through a full bedding procedure without the car’s brakes getting even more spongy. If I try to stop hard from 30mph a couple times then the pedal will almost go to the floor after even 2 stops. …. But the rear brakes seem to be working much harder than the front. They will even smoke from using them so hard during a couple hard braking procedures, as in a brake bedding procedure.

So after having lived with these spongy, not so great brakes I decided to do something about it this week. I figured it HAD to be the front brake pads. I’ve got a set of cross drilled/slotted rotors, but my 20 year old 4000# truck will stop way before this car will. I picked up a set of semi-metallic titanium pads and proceeded to change the front. I even changed both front flexible hoses then bled the entire system, including the master cylinder, just as the Helms manual tells you how to. But guess what, I still have the same spongy feeling in the pedal. The system does not have any leaks as the level in the master cylinder never drops, so I am really at a loss as to what causes this lack of brake performance. When I bleed the brakes there is no air left coming out of the bleeders.

I do not think the fronts are working as hard as they should. Some items of concern I had when changing the front pads were the abnormal wear they had. The inner pads had significantly more wear than the outer. It was a very abnormal wear as the inside of the inner pad was worn significantly but the outer edges were not. It only seemed to wear where the piston was pushing it against the rotor. Weird… but I thought I’d mention it anyway. I know some of you will come back with suggestions to change the bushings, but I don’t see a need to as I liberally coated the inside with grease and was able to push the pins into the bushings by hand… easily too to note. So can you guys help me out with this one. The bottom line is: The brake pedal is spongy, it gets even more spongy with hard braking, the car doesn’t stop worth a darn, the brakes have been bled, bled and bled again. So what to do… I’m at a loss!!!!!

[BigCat83]

When you step on the brake pedal does it slowly but continually go all of the way to the floor?

If so the seals in the brake master cylinder may be leaking and it may need to be replaced.

Just an idea.

Also, some(all?) ABS systems need to have the valves in the ABS master cylinder cycled (with the appropriate tester) while bleeding the brakes to do the job peoperly...

[BostonETC97]

Had a very similar problem on an old Benz. You could stand on the brake pedal and not much would happen. Sometimes I'd even be pumping the brakes to get the car to stop. I replaced the master cylinder, all four calipers, pads, and rotors. No improvements worth noting. Finally I found a true german mechanic who asked if I had ever changed the rubber brake lines. My answer of "no" fixed all my problems.

When he replaced the lines, he showed me how much my old rubber lines had swollen closed. Although they looked "ok" on the outside, the insides of the lines had shrunk up, and with a slight bit of rusty 'mud' residue in them, had been deemed nearly useless. After the installation of all new rubber lines, the brakes and stopping power were restored to "amazing." Total cost was $20 per wheel with parts and labor... that after spending probably $1600 on components that probably weren't even needed.

-Scott

[boatboy]

Had a very similar problem on an old Benz. You could stand on the brake pedal and not much would happen. Sometimes I'd even be pumping the brakes to get the car to stop. I replaced the master cylinder, all four calipers, pads, and rotors. No improvements worth noting. Finally I found a true german mechanic who asked if I had ever changed the rubber brake lines. My answer of "no" fixed all my problems.

When he replaced the lines, he showed me how much my old rubber lines had swollen closed. Although they looked "ok" on the outside, the insides of the lines had shrunk up, and with a slight bit of rusty 'mud' residue in them, had been deemed nearly useless. After the installation of all new rubber lines, the brakes and stopping power were restored to "amazing." Total cost was $20 per wheel with parts and labor... that after spending probably $1600 on components that probably weren't even needed.

-Scott

Boston - Well I did replace both front lines and I also did the rear cross-over line in the past... I haven't done the two rear lines... but like I said the rears seem to work great. So I'm at a loss again. I think I will definitely do that next, if not for that, then even just for preveventative maintenance, as I do put a lot of miles on my car.

When you step on the brake pedal does it slowly but continually go all of the way to the floor?

If so the seals in the brake master cylinder may be leaking and it may need to be replaced.

Just an idea.

Also, some(all?) ABS systems need to have the valves in the ABS master cylinder cycled (with the appropriate tester) while bleeding the brakes to do the job peoperly...

BigCat - I have thought of replacing the master cylinder next anyway. Like I said the pedal is spongy BUT it does not go all the way to the floor when pressed.

I have thought that perhaps there was something w/ the ABS system that would have to be cycled... but everything I've read either in the manual or elsewhere has said that bleeding the brakes is the same with or without the ABS. (Just pump the pedal and bleed) Anyone know if this is the case for a 96 Deville????????

I'm almost tempted to call the Stealership and ask them about brake bleeding and if it involves any special procedures for the ABS... but I usually try to avoid that place at all costs.

[MAC]

GM's 1994 Service Manual (Volume 2, page 5-8) states the following regarding uneven braking (front to rear):

1. Make sure the rear brakes are adjusted correctly. Uneven braking could be caused by maladjusted rear brakes.

2. Improper rear actuator adjustment causing uneven braking

3. Parking brake not releasing

4. Master cylinder may be leaking

5. Restricted brake fluid passage (master cylinder)

6. Sticking caliper piston

7. Faulty proportioner valves

Considering you have bled the system, I assume it is free of air and that you are using the correct brake fluid.

[BodybyFisher]

I have a 96 Deville and the brakes are very good. If you are sure you have bled the brakes good, which is sounds like you did, then I would look toward your master cylinder. Press and hold your brakes and see if the pedal goes to the floor.

[epricedright]

Sounds like the master cylinder or power booster to me, the latter being more likely if it takes a lot of effort to stop the car. I had a power booster let go once, but I can't recall for sure if the pedal was spongy...the more I think about it, I think the pedal become harder to push, and the brakes hardly worked, which makes sense being it's vacuum operated and when the diaphram goes, the brakes lose their "boost".

[boatboy]

I'll try replacing the master cylinder next and see where that takes me!

Thanks for the input.

[BodybyFisher]

I'll try replacing the master cylinder next and see where that takes me!

Thanks for the input.

epriced brings up a GOOD possibility, check you vacuum boost unit before you replace your master cylinder! If your pedal is not drifting down at stop lights (a clear sign its messed up), I would be careful replacing it before I checked the booster

[epricedright]

If your car is requiring increased pedal effort and increased distances to stop, then I'd suspect your vacuum booster. To check the vacuum booster, pump the brake pedal with the engine off until you've bled off all the vacuum from the unit. Then hold the pedal down and start the engine. You should feel the pedal depress slightly as engine vacuum enters the booster and pulls on the diaphragm. No change? Then check the vacuum hose connection and engine vacuum. If okay, the problem is in the booster and the booster needs to be replaced.

If you have a spongy/soft pedal, then I'd lean more towards a leaking master cylinder, air in your lines, or a leaking caliper/line. Do you see any fluid on your master cylinder, power booster, calipers or brake lines? Are you having to add fluid at all? Sometimes fluid will leak from your master cylinder into your booster.

[The Fred]

It's the booster!

[Regis]

Sounds like a master cylinder issue to me but it just might be the brake booster module. And since the brake booster module costs around $40 plus 15 seconds of installation time I would try this first. Like the others are suggesting, no sense in spending a lot when the fix might only be a little.

[boatboy]

I'll check the booster too. There is no increased pedal effort when depressing it. epriced gives a good method for checking the boost. Lets see what I find there.

[BodybyFisher]

Sounds like a master cylinder issue to me but it just might be the brake booster module. And since the brake booster module costs around $40 plus 15 seconds of installation time I would try this first. Like the others are suggesting, no sense in spending a lot when the fix might only be a little.

Regis, its possible that we are talking about different things, you said module.. I was under the impression we are talking about the brake booster, that is the big unit that the master cylinder is bolted to... Replacing the booster is a HUGE job, and I believe it entails removing the master cylinder and unbolting bolts from under the dash, never a fun thing to do. I would dread having to replace the booster. Rock auto has a booster (Cardone) for $94..

[KHE]

Have you verified that none of the brake lines are leaking? If not, trace all the lines from the master cylinder to each caliper looking for leakage. If you don't see any leakage, I would bet the master cylinder is bad.

[boatboy]

I have not verified that any of the brake lines are leaking. Nothing is visible... but I have not done a thorough inspection taking the time to physically verify each and every inch of them. I did remove the master cylinder and notice that there is some brake fluid on the power booster. So perhaps the MC is leaking some fluid on the Power booster. Replacing the MC is my next step. I just sent an email to Brasington requesting a price for one. We'll see what they come back with. The other option is to get one from Advance Auto. They have a new Bendix for $140 and a Raybestos for $315.

[epricedright]

I have not verified that any of the brake lines are leaking. Nothing is visible... but I have not done a thorough inspection taking the time to physically verify each and every inch of them. I did remove the master cylinder and notice that there is some brake fluid on the power booster. So perhaps the MC is leaking some fluid on the Power booster. Replacing the MC is my next step. I just sent an email to Brasington requesting a price for one. We'll see what they come back with. The other option is to get one from Advance Auto. They have a new Bendix for $140 and a Raybestos for $315.

Sounds like it's your master cylider then. There shouldn't be any fluid on your booster. partszoneonline.com has your OEM MC for $186 and rockauto.com has a Raybestos (PG Plus) for $142

Be sure to clean any brake fluid off the booster. The fluid can deteriorate the rubber diaphram in the booster. Just curious, did you check the booster before removing the MC?

[BodybyFisher]

Are you losing brake fluid, I did not pick up on that in the prior posts? That is an entirely different story. I don't believe you stated you needed to add fluid.

Sometimes as someone mentioned above the MC can leak at the rear, into the booster and the fluid can be sucking into the engine vacuum system. If you see fluid at the rear its possible you have seepage, but I would think you would need to add fluid, occasionally...

[epricedright]

Are you losing brake fluid, I did not pick up on that in the prior posts? That is an entirely different story. I don't believe you stated you needed to add fluid.

Sometimes as someone mentioned above the MC can leak at the rear, into the booster and the fluid can be sucking into the engine vacuum system. If you see fluid at the rear its possible you have seepage.

Great...Now I'm just a "someone".

[BodybyFisher]

Sorry Epriced, but at least I gave you credit! I didnt want to re-read the above posts to find who made the statement, BUT!, I did remember! Let me correct my statement:

Sometimes as EPRICED mentioned above the MC can leak at the rear

Better?

[epricedright]

Sorry Epriced, but at least I gave you credit! I didnt want to re-read the above posts to find who made the statement, BUT!, I did remember! Let me correct my statement:

Sometimes as EPRICED mentioned above the MC can leak at the rear

Better?

Very good! Bold, Underlined and Italics....I like it! Hey BBF, how about EPR? Would that be easier to type?

[zonie77]

Boatboy,

In the first post you described uneven pad wear. Have you replaced or rebuilt the front calipers? Have you cleaned all the sliding surfaces (not just the guide pins) for the calipers?

It sounds like the front calipers may be stuck.

[adallak]

Sorry Epriced, but at least I gave you credit! I didnt want to re-read the above posts to find who made the statement, BUT!, I did remember! Let me correct my statement:

Sometimes as EPRICED mentioned above the MC can leak at the rear

Better?

Very good! Bold, Underlined and Italics....I like it! Hey BBF, how about EPR? Would that be easier to type?

I am for full user names. The abbreviated versions leave too much room for ambiguity... BBF - Bureau for Better what? EPR – kind of fuel pressure regulator.

[epricedright]

Boatboy,

In the first post you described uneven pad wear. Have you replaced or rebuilt the front calipers? Have you cleaned all the sliding surfaces (not just the guide pins) for the calipers?

It sounds like the front calipers may be stuck.

Zonie, I was wondering the same thing, but I was more interested in helping fix the spongy pedal first..they appeared to be two different problems. Boatboy, did you use silicone grease and not petroleum grease for your slider pins? The pins will slide at first with petroleum grease, but will later cause the boots to swell and will seize on the pins. Something is hanging up causing your pads to wear unevenly. I had to use a dremel tool and a wire brush attachment on my drill to clean up the contact/sliding areas (rust and uneven high spots) where the calipers slide on the knuckle. I even put a dab of grease in spots. If that's not it, then I would suspect the caliper bore is rusted and the piston is sticking. I would be sure and check your calipers and make sure they're not leaking before replacing your master cylinder, although if you're leaking at the MC, then it definately needs to be replaced.

[epricedright]

Sorry Epriced, but at least I gave you credit! I didnt want to re-read the above posts to find who made the statement, BUT!, I did remember! Let me correct my statement:

Sometimes as EPRICED mentioned above the MC can leak at the rear

Better?

Very good! Bold, Underlined and Italics....I like it! Hey BBF, how about EPR? Would that be easier to type?

I am for full user names. The abbreviated versions leave too much room for ambiguity... BBF - Bureau for Better what? EPR – kind of fuel pressure regulator.

If only I had known I would have liked this site as much as I do, I would have come up with a better (shorter?) name. I was more interested in promoting my eBay seller name when I signed up.