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  #1  
Old 02-08-2010, 11:48 PM
hd wood
 
Join Date: Oct 2007
Location: South Jersey
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Intermittent 124 Brake Failure?

Anyone familiar with a condition where, occasionally, you step on the pedal and it is hard (no travel) and no braking action. When you release the pressure and try again the system functions properly.

This only occurs from time to time.

Lites function on the cluster.



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  #2  
Old 02-09-2010, 03:20 AM
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I have noticed similar with my 1990 300d.
I noticed when washing the car that one rear disc has not been doing any work,the caliper has seized.
Odd pedal feel and abs kicking in at around 2mph as I come to a stop.
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  #3  
Old 02-09-2010, 09:24 AM
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issue with the brake servo or vacuum to the servo?
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  #4  
Old 02-09-2010, 10:47 AM
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Quote:
Originally Posted by hd wood View Post
Anyone familiar with a condition where, occasionally, you step on the pedal and it is hard (no travel) and no braking action. When you release the pressure and try again the system functions properly.

This only occurs from time to time.

Lites function on the cluster.



Comments?

Has your 124 been hanging out with the new Prii, (whatever the plural of Prius is)?
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  #5  
Old 02-09-2010, 10:47 AM
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What? Did MB sun-contract out their brakes to Toyota?
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  #6  
Old 02-09-2010, 11:36 AM
hd wood
 
Join Date: Oct 2007
Location: South Jersey
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Smile 300Dt brake funcion

Quote:
Originally Posted by punkinfair View Post
issue with the brake servo or vacuum to the servo?
No idea of the cause. Basic hydraulic functions are pretty reliable. I think it may have to do with the ABS system. It's a bit difficult because my son has the car although I have experienced the problem. It doesn't happen very often and lasts for only a few seconds.

I have access to two retired MB guys so when I get it figured out I'll post it.
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  #7  
Old 02-09-2010, 11:37 PM
hd wood
 
Join Date: Oct 2007
Location: South Jersey
Posts: 60
My first sensible response has been 1) clean all the abs sensors on the wheels and purge the air out of the system. This might well clear things up. Still waiting to be able to talk to main mb guys. Let you all know. Thanks. Oh, Prii might in fact be correct.
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  #8  
Old 02-09-2010, 11:51 PM
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Hey! When you find out what the problem is with your brakes, you may want to let the guys at Toyota know. They have been having vaguely similar problems with their hybrid!! Has you MB friend just got a job at Toyota?? HAHAHAHA !!!

Seriously it does sound like you have an ABS problem as you have a firm peddle. My second suggestion would be a vac problem, low vac will make it feel like you need a 10 ton foot to slow the car.
I hope you are not trying to drive it at the moment!!
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  #9  
Old 02-10-2010, 10:59 AM
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You don't say whether the car is gas or diesel - it makes a difference.

If it's a petrol powered vehicle, I would replace the brake booster and be done with it. 99.999% chance this is the problem. Look for brake fluid in the booster; if present you need a master cylinder too.

If there's no pulsing in the pedal, you don't have an ABS problem.

If the car is diesel powered, then it could be either the booster or vacuum pump. Still, I'd start with the booster.

Since it's a 124, how old are the flexibile brake lines? If much past 10 years, then it's time to consider changing them as well.
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  #10  
Old 03-02-2010, 10:17 AM
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This is happening on my W124 also.

I replaced the brake booster line thinking I was having a problem with my "Non Return Valve", because when the brakes have no vacuum assist the engine will not turn off either.

As you know, the engine shut off gets it vacuum from the brake booster line, and the "Non Return Valve" is supposed to keep a vacuum for the brakes and the engine shut off even when the engine is off. My thought was the valve was getting stuck in a closed position not allowing "fresh" vacuum into the brake booster and the shut off actuator.

The new booster line did not correct the problem, much to my surprise.

My vacuum pump makes a little noise, and since it is 17 years old with 150,000 miles I will replace it next as a preventative measure.

If after the new pump I still have the stiff brake problem, I suppose it can only be the brake booster itself. That would be surprising because it holds vacuum all night, has no brake fluid in it, and works perfectly after the first cold startup period every day.

But MB diesels are full of surprises, aren't they?
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  #11  
Old 03-02-2010, 03:50 PM
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Quote:
Originally Posted by jcyuhn View Post
You don't say whether the car is gas or diesel - it makes a difference.
Does the fact that the question was posed in the Diesel Discussion provide no clue?

That said, full disclosure of year/model is seldom a bad thing.
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  #12  
Old 03-02-2010, 05:52 PM
Starstruck
 
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Quote:
Originally Posted by Murkybenz View Post
I have noticed similar with my 1990 300d.
I noticed when washing the car that one rear disc has not been doing any work,the caliper has seized.
Odd pedal feel and abs kicking in at around 2mph as I come to a stop.
Clean the ABS sensors on the front axle.

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