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  #1  
Old 05-19-2010, 10:05 AM
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Master cylinder and brake booster diy?

My brakes on the 83 300d are less than perfect even with new rotors and pads, so i am going to change the booster and master cylinder to complete the job.
Does anyone know what the symptoms for a bad booster are versus for a bad master cylinder?
My main problem is that on a hill i do not feel as if brakes are completely engaging, im leaned towards it may be the master cylinder but both parts are really old.
A concern for me is cost because the booster is much more costly.
Anyone have any tips?
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  #2  
Old 05-19-2010, 10:20 AM
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Originally Posted by europower View Post

Anyone have any tips?
From your description of the problem, it sounds to me like you might be working on the wrong end of the brake system.
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  #3  
Old 05-19-2010, 10:33 AM
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New rotors, pads and sensors, purged all old fluid and air out of the system.
What else is there?
Thanks
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  #4  
Old 05-19-2010, 10:35 AM
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agreed, it sounds to me like you have caliper issues.
how did your pads look? what was wrong with the rotors before you changed them.
a bad booster will cause the brake pedal to be very hard to push.
a bad Master Cylinder will cause the pedal to fall to the floor, without affecting stopping power, or it could give stopping power, but the pedal will not hold etc.
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  #5  
Old 05-19-2010, 10:44 AM
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The rotors were old and thinned out, the pads were also as thin as crackers, the ate calipers did seem ok to me at first sight, how can i tel if calipers were bad, there was no sign of leaking and piston seemed normal.
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  #6  
Old 05-19-2010, 11:41 AM
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Is it possible that either the rear or the front isn't working due to a bad master cylinder?

I had a master cylinder partially fail on another car I use to own. It was a dual circuit master circuit, one for the front and one circuit for the back. The back brakes essentially didn't work, so I only had half my brakes.

I honestly do not know if this is possible with Mercedes master cylinders.
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  #7  
Old 05-19-2010, 11:41 AM
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Originally Posted by europower View Post
What else is there?
Hoses are a common source of trouble.
Did you clean the calipers and lube the new pads?
Any chance your bleeding job was less than 100%?
Sometimes new pads and rotors will feel a little "slick" initially.
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  #8  
Old 05-19-2010, 12:03 PM
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Originally Posted by toddyvol View Post
Is it possible that either the rear or the front isn't working due to a bad master cylinder?

I had a master cylinder partially fail on another car I use to own. It was a dual circuit master circuit, one for the front and one circuit for the back. The back brakes essentially didn't work, so I only had half my brakes.

I honestly do not know if this is possible with Mercedes master cylinders.
sure this could happen, but the pedal would drop to nearly the floor.
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  #9  
Old 05-19-2010, 01:45 PM
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Get a helper

Quote:
Originally Posted by europower View Post
The rotors were old and thinned out, the pads were also as thin as crackers, the ate calipers did seem ok to me at first sight, how can i tel if calipers were bad, there was no sign of leaking and piston seemed normal.
Get a helper to apply the brakes for you and check to make sure that the pistons in the calipers are not sticking... whilst you are there you may see some other problem such as too much bulging in the flexible lines.

My understanding of the brake booster is that with out it it would just be harder to apply the brakes - no vacuum power assistance you see?
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