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Brake problems

I bought a 2001 chevy malibu about a month and a half ago.when I test drove it,didnt notice any problems or leaks…after driving it for a 2 weeks…the brake pedal would drop to the floor while driving and then if I hit it again real quick it would be ok…this problem would happen now and then…we replaced the right front caliper thinking that it was sticking and bled all the brakes…There was air in the system…everything was fine for about two more weeks then while driving the pedal would get hard when applied and then drop again…not all the way to the floor,and it alternates that way…what are your thoughts?I dont have much money to fix this problem so any cheap solutions would be appreciated:)

You have a failing Master Cylinder. Have this towed to a shop and repaired ASAP or one day very soon you’ll hit the brakes and be totally unable to stop.

Do not procrastinate. This one is serious.

You’re describing a brake master cylinder that’s leaking internally. Replace the brake master cylinder


The bad news is that this often isn’t cheap. The last shop gave me a $600+ estimate to do it. You can do it yourself for about $70 in parts, if that, but I caution you to only do it yourself if you know what you are doing, or you have a friend who knows what they’re doing and will help you. It’s an easy job, but it’s not one that you want to mess up on.

@shadowfax -

According to (which I’ve found to be pretty accurate around here), a MC replacement on this car should cost $216-408 here, depending on where you go.

@nutty -

These guys are 100% correct - do NOT waste any time getting this fixed. I personally would not drive the car AT ALL until it is fixed - it simply isn’t safe and you’re opening yourself up to liability problems if you hit someone. Shadowfax’s parts estimate is dead-on, but don’t forget to add in a few bucks for new brake fluid. The positive is that if you can install your own caliper, there’s no reason you can’t do this fix, too… but if you don’t feel up to it, the extra charge for a shop to fix it isn’t that steep a price in this case.

If you do decisde to replace the MC yourself, post back. We may have some suggestions, like making sure you bench bleed the master cylinder before installing.

Thank you guys for responding…very much appreciated…we are doing it ourselves…my hubby has done one before but on a different car a long time ago but he knows what hes doing…we have the cylinder off now and leaving soon to pick up the new one…picking up at advanced auto for 50 bucks…my brother got me a 35 dollar off coupon:).my other question is this…hubby has aanother mechanic friend that is convinced its the abs modulator or the power booster…but car doesnt make any noise at all when the brake is pressed…I sure hope it isnt…dont have the money for those…not cheap…your thoughts on that?..ty guys again

Thanks for the follow up. Sincere best.

It ain’t the modulator. Modulators present failures entirely differently and would not allow the pedal to go to the floor even if they failed.

It also ain’t the booster. Like the modulator, a failed booster will not allow the pedal to sink to the floor. The booster only helps push the rod that goes into the MC. The hydraulic fluid foreward of the MC pistons is what keeps the pedal from sinking to the floor, and the booster has no affect on that.

ty for replying…could you tell me what those failures would look like just so i know what to keep my eye out for

and question 2…should i be replacing the left front caliper soon since we did the right one already?

The modulator, part of the ABS system, is basically four small valves, one in each brake line, each one activated by an electrical solenoid. When the ABS system detects a wheel having lost traction, it pulsates the valve in that brake line. Failure can manifest itself in a constant pulsating, as if you had one whele that never turns, or in loss of the pulsation, which would manifest itself in the brakes not pulsating is a wheel loses traction. It cannot fail in a way that would allow the oedal to sink to the floor.

The booster is a diaphragm between the brake pedal and the rod going into the master cylinder. When the rod is moved from the brakes being applied, the engine vacuum is applied to the front of the diapphragm and it helps push the rod. Failure of this would not allow the pedal to sink to the floor. Failure of the booster would manifest itseaf as a harder than normal brake pedal. While I did notice that you commented on the pedal changing feel, thst symptom needs to be combined with the others to make a diganosis. And your sinking pedal ruled out the booster.

As to the other caliper, without knowing how many miles are on the car it’s hard to guess. sometimes one caliper will fail prematurely. But if it helps you sleep better, my answer would be yes.

thank you so much for your input…I will sleep better tonite:)…I can be an impatient person and want things fixed right away…but when it comes to brakes…gotta have those…my car has 126,000 miles but a newer engine was put in about 2months ago with 81,000 miles on it…so needless to say i thought this car would be a better bargain for the amount i paid for it…hopefully i can get all the kinks ironed out of it…you seem very knowledgable and will come to you guys with my questions over anyone else…ty again

Honestly regarding replacing both sides when you replace one caliper, I don’t see why. I’ve heard mechanics say things like “well the internal volume of one might be different than the other which would cause braking problems,” but that doesn’t jive with me, because if the internal volume of one is slightly different, the fluid will equalize because that’s what fluids do. I’ve been doing brake work for years now on my cars, and I only replace what’s broken. It’s never been a problem yet.

well we got the master cylinder in with no problems but getting it off was a pain,trying to reach the bolts that hold it on.when we took off the rear tires to bleed the rear brakes we noticed 2 things.The emergency brake wasnt working well so wasnt gonna stop me if needed.We noticed that the adjuster lever was put in backwards…and the adjuster screw assembly came apart and half the part was laying inside.(hopefully I have the part names right).This was on the left side…On the right side we noticed that one end of the dust cap that is on the wheel cylinder has a rip in it.(we didnt notice this 2 weeks ago when we bled the brakes after putting the caliper on).Also both cylinders have alot of corrosion on them and cant pull the dust cap to see if leaking but have not seen any signs of leaks on either cylinder at all…So we put Red RTV on the rip till i need to buy new cylinders.We have not bled the front brakes yet but we did take it for a test drive so far and I have brakes again…we will bleed the front tonite or tommrow…Any thoughts would be appreciated:)

Get the car up on jack stands, level, and bleed ALL the brakes in the same session. Brakes are criss-crossed on the car, so the front left and the back right are linked, as are the front right and back left. This means that in bleeding the rear brakes, you bled half of each line. It’s possible that air from the front end of the system has now worked its way back to the back end of the system.

Don’t forget to keep checking the level in the MC while bleeding - it’s annoying to have to start over because you let it get too low and it sucked air.