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GDawgC220
11-23-2003, 03:27 PM
Hey all,
A while ago, I went to the dealership to see about my mushy brakes. They flushed the system (hadn't done it in a while) and it felt somewhat better, but bad news was that the Brake Master Cylinder was starting to wear out (age and usage).

Nowadays, some days, it feels great, very responsive on braking...then some other days, its really mushy, gotta push it down to get the car to slow. How long does it take for it to wear completely out and can I still stop the car if say it goes while i'm driving? I've heard that it can still go for a long time or fast after you've found out...

Is the master cylinder something to DIY? Dealer quoted about $600 to do...thanks guys for your help.

-G-

marksbenz
11-23-2003, 03:55 PM
Dont wait till it goes bad. I recently change mine. I went to a ind. Mercedes shop. Its cost me $400.00 to change. And now my brakes feels more responsive. Get it change before it goes. Dont mess with the brakes.

moebiusgold
11-23-2003, 04:13 PM
If you step on the brakes and the pedal slowly moves to the floor you have a bad mastercyclinder. All sorts of stuff can make the brakes mushy. Bad rubber hoses, loose wheel bearings, pads worn tapered, slimmy black stuff that doesn't come out unless you dissassemble all of the cylinders. All of this stuff is DIY as far as I am concerned. You know your level of mechanical expertise and tools, not me. You need metric crows feet. You don't need fancy bleeding equipment if you don't mind waisting a little brake fluid. Unless there are pits I don't replace cylinders and I frequently put them back together with the same seals. But then with your miles I'd have had my brakes apart 4 or 5 times. Change the fluid every 1 or 2 years and the cylinders last. My 116 has 2 of 4 orig wheel cylinders at 480k. Would have had them all but a dust seal got cut and I couldn't buy a rebuild kit. Good luck

GDawgC220
11-23-2003, 04:48 PM
what would it be like if I tried to stop without the cylinder? No power braking feeling, like if u have it in neutral and the car is rolling and trying to apply the brakes really hard? Thanks for your help guys.

-G-

moebiusgold
11-23-2003, 04:53 PM
Originally posted by GDawgC220
what would it be like if I tried to stop without the cylinder? No power braking feeling, like if u have it in neutral and the car is rolling and trying to apply the brakes really hard? Thanks for your help guys.

-G-

You mean with no power brake booster?

GDawgC220
11-23-2003, 04:57 PM
Originally posted by moebiusgold
You mean with no power brake booster?

Yea, I guess that's what I meant.

-G-

GDawgC220
11-23-2003, 05:16 PM
Originally posted by moebiusgold
If you step on the brakes and the pedal slowly moves to the floor you have a bad mastercyclinder. All sorts of stuff can make the brakes mushy. Bad rubber hoses, loose wheel bearings, pads worn tapered, slimmy black stuff that doesn't come out unless you dissassemble all of the cylinders. All of this stuff is DIY as far as I am concerned. You know your level of mechanical expertise and tools, not me. You need metric crows feet. You don't need fancy bleeding equipment if you don't mind waisting a little brake fluid. Unless there are pits I don't replace cylinders and I frequently put them back together with the same seals. But then with your miles I'd have had my brakes apart 4 or 5 times. Change the fluid every 1 or 2 years and the cylinders last. My 116 has 2 of 4 orig wheel cylinders at 480k. Would have had them all but a dust seal got cut and I couldn't buy a rebuild kit. Good luck

On some days, it is fine and I step and by half way down, the car stops. Some other days, it seems like I have to press the brake so far to get it to stop...so these are symptoms?

What's a good price to get this replaced?

-G-

CKlasse
11-23-2003, 06:26 PM
From reading your posts, I would say it's either leaky master cylinder or vacuum leak to your power booster.

Master cylinder is extremely easy to rebuild if you are mechanical incline, and vacuum leak is simply a matter of replacing hoses.

Good luck to you

GDawgC220
11-23-2003, 06:28 PM
Originally posted by CKlasse
From reading your posts, I would say it's either leaky master cylinder or vacuum leak to your power booster.

Master cylinder is extremely easy to rebuild if you are mechanical incline, and vacuum leak is simply a matter of replacing hoses.

Good luck to you

When you say the vacuum leak...I hear this cycling noise in my trunk whenever the car is on (powered up, doesn't have to be started, but whichever, it will be doing the noise)...the noise is coming from the rear right quarter of the trunk somewhere. Could this be the vacuum leak?

-G-

CKlasse
11-23-2003, 06:50 PM
Wrong vacuum leak. The one you are talking about controls the door locks, trunk lock, rear head rest etc.

Look at your brake booster. See the hose that goes into your intake manifold? That's the one :)

GDawgC220
11-23-2003, 07:00 PM
how can i tell if it's leaking? hissing sound?

-G-

and if it is, where can i get the tube/hose from? thanks for your help man.

moebiusgold
11-23-2003, 08:41 PM
Umm. A vac. leak would make the idle get all screwed up. It would introduce air on the wrong side of the MAS. Do you have equal braking power for equal pedal push all of the time? Is the only difference the pedal position? If so it is the master cyclinder or loose wheel bearings. Does speed of application have anything to do with it? If I put my C36's brakes on with about 40 lbs of force and I am into the ABS. Ther is no more after that. Just a little more than an inch of travel at this point. Sounds like you might not have the tools to do the job. Hunt around for an independant garage. Estimates are easy to get.

GDawgC220
11-24-2003, 03:25 AM
Originally posted by moebiusgold
Umm. A vac. leak would make the idle get all screwed up. It would introduce air on the wrong side of the MAS. Do you have equal braking power for equal pedal push all of the time? Is the only difference the pedal position? If so it is the master cyclinder or loose wheel bearings. Does speed of application have anything to do with it? If I put my C36's brakes on with about 40 lbs of force and I am into the ABS. Ther is no more after that. Just a little more than an inch of travel at this point. Sounds like you might not have the tools to do the job. Hunt around for an independant garage. Estimates are easy to get.

Not always equal braking power at same brake position. Say, today, it may be push half way down and the car will almost be at a stop...like there is resistance at half way.

other days, there's about an inch left till I hit the floor and the car will stop (not all the way to the floor, but about an inch - inch 1/2 left of travel space).

So I guess you can say it varies day to day, either a lot of travel or a little and braking results are different. Obviously, sometimes i don't realize it and when I hit it half way, oh sh*t, its not stopping, then I have to go much further. Sometimes it's sensitive and I over brake too early.

-G-

CKlasse
11-24-2003, 07:09 AM
Your brake might be 'fading' ? Inspect the pads and rotors themselves.

GDawgC220
11-24-2003, 07:50 AM
Originally posted by CKlasse
Your brake might be 'fading' ? Inspect the pads and rotors themselves.

At times, they do make a squeeling sound when i come to a stop...almost screech like.

-G-

vas2vas
11-24-2003, 08:03 AM
Originally posted by GDawgC220
Hey all,
A while ago, I went to the dealership to see about my mushy brakes. They flushed the system (hadn't done it in a while) and it felt somewhat better, but bad news was that the Brake Master Cylinder was starting to wear out (age and usage).

Nowadays, some days, it feels great, very responsive on braking...then some other days, its really mushy, gotta push it down to get the car to slow. How long does it take for it to wear completely out and can I still stop the car if say it goes while i'm driving? I've heard that it can still go for a long time or fast after you've found out...

Is the master cylinder something to DIY? Dealer quoted about $600 to do...thanks guys for your help.

-G-

well for the mileage of your car a master cylinder failure is not that uncommon, especially if it was driven hard over the years..... like anything related with brakes DIY means betting your life on your skills.... if you're confident about that go ahead, otherwise leave it to a professional..... still $600 sound a little steep, what is the part vs labor split.... better to get a 2nd opinion first.....

vas2vas
11-24-2003, 08:12 AM
Originally posted by GDawgC220
When you say the vacuum leak...I hear this cycling noise in my trunk whenever the car is on (powered up, doesn't have to be started, but whichever, it will be doing the noise)...the noise is coming from the rear right quarter of the trunk somewhere. Could this be the vacuum leak?

-G-

hmm from the right side of the trunk... I'll bet it has something to do with the power locks system..... there is a kneumatic pressure reservoir / distribution module or accessory pump of some sort (I think that's what it is please correct me if I'm wrong) for the central locking behind the carpet panel on that side of the trunk, it might be faulty, or one of the pipes leanking..... causing it to work more to compensate for the loss of pressure.....
I found it when I fixed my problem with the gas cap not locking/unlocking..... (was just a misalignment problem in my case) no pictures, sorry :( ....
one easy way to look for leaks is to blow cigarette smoke in the system and see where it comes out from.....

moebiusgold
11-24-2003, 06:35 PM
The vaccum pump you are talking for is for everything but the Brake booster that is powered by Vac. If it stays on or keeps comming on with the key on but engine not running, you have a different problem.
If you step on the brake pedal without the engine running you'll quickly use up all of the stored Vac. Listen and feel. You foot will end up moving less and less with the same amount of force. If you find out that there is no Vac. after the car sits until you run the engine, then it is ~ for sure bad.
Once the Vac. is all used up, try stopping the car. Many times the effort is required. If you actually do that be real careful. Anyone that has had a car die while rolling down the road will tell you how fun all of those power accesories are.
If you haven't been through all of the rest of the brake system with that many miles its way past due. ;)
If I had to guess I would lean a long way towards the master cylinder.;) Good luck!

moebiusgold
11-24-2003, 06:40 PM
Oops, I meant:
If you step on the brake pedal without the engine running you'll quickly use up all of the stored Vac. "in the power brake booster".
I am refering to the Booster after this.

GDawgC220
11-24-2003, 07:07 PM
Originally posted by moebiusgold
The vaccum pump you are talking for is for everything but the Brake booster that is powered by Vac. If it stays on or keeps comming on with the key on but engine not running, you have a different problem.
If you step on the brake pedal without the engine running you'll quickly use up all of the stored Vac. Listen and feel. You foot will end up moving less and less with the same amount of force. If you find out that there is no Vac. after the car sits until you run the engine, then it is ~ for sure bad.
Once the Vac. is all used up, try stopping the car. Many times the effort is required. If you actually do that be real careful. Anyone that has had a car die while rolling down the road will tell you how fun all of those power accesories are.
If you haven't been through all of the rest of the brake system with that many miles its way past due. ;)
If I had to guess I would lean a long way towards the master cylinder.;) Good luck!

Yea, if I have had my car off for a while and just pump the brakes, I can get it to go down a few times without effort, then it starts to resist (vac pressure runnin out)...so it still working, just wearing out. probably gonna have them check it out at my oil change, which is due in about 1,000 miles and that takes me no effort to reach ;)

-G-