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  #1  
Old 07-24-2001, 10:45 AM
benzat
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my master cylinder I think keeps locking up.

when I drive the car I can smell the brake pads burning.

brand new calipers pads hoses
it doesnt happen all the time. would it be better to replace the master cylinder or rebleed the brakes? the master cylinder is 20 years old

any advice? and pricing a new one Ive found them for (new) $50.00 and $250.00 for the same part?


thanks
benzat
1982 380 SEC
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  #2  
Old 07-24-2001, 12:34 PM
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Location: New York City Burbs
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In my experience, when master cylinders go bad they fail to give enough pressure due to worn seals. I have never heard of one 'locking'.
Do you have a firm pedal? Mooshy pedal? fades and have to pump up? Park brake off? Fluid level change?

I would pull each wheel and check each caliper to see if that is the culprit. I bet ya that there's a bad one. There is alot to look at here.
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'84 190E 2.3
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  #3  
Old 07-24-2001, 01:16 PM
WDurrance
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Usually when the master cylinder goes bad it won't hold enough pressure. The place to look is at the individual wheels. See which one(s) is(are) getting hot, then check from there to find the sticking caliper. Over time the brake hoses deteriorate and allow pressure to pass through but won't let it release all the way. An easy way to check is to loosen the bleeder screw and see if fluid will run out on its own. If it won't drip, you need brake hoses.
Regards,
Randy D.
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  #4  
Old 07-25-2001, 12:36 AM
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Join Date: Jun 1999
Location: Los Angeles, Calif, USA
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Someone posted a message in the past saying that sometimes a bad master cyl valve cause the rear caliper problems. The valve sticks closed and does not allow fluid back to the master cyl resulting in brake drag, overheat, and fading.

David
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  #5  
Old 07-25-2001, 12:45 AM
WDurrance
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Quote:
Originally posted by be459
Someone posted a message in the past saying that sometimes a bad master cyl valve cause the rear caliper problems. The valve sticks closed and does not allow fluid back to the master cyl resulting in brake drag, overheat, and fading.

David
That particular problem seems to occur on the 126 chassis when the reservoir is "cleaned" with solvent. Due to the reservoir design, the solvent("brake clean")remains in the reservoir for the rear brakes and causes the seal in the master cylinder to swell. I've seen it several times.
Randy D.
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  #6  
Old 07-25-2001, 01:22 AM
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Randy,

Thank you for the additional information.

David
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  #7  
Old 07-25-2001, 01:57 AM
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Join Date: Apr 2001
Location: Beech Island, S.C.
Posts: 468
The master cylinder is the main cause of lockup. I would check each wheel though and find the one that is locked up if only one and if you can break the bleeder screw and it frees up that wheel your likley to have a clogged flex hose to that caliper.
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