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Old 10-19-2009, 02:44 PM
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On my 123, my problem was caused by the metal clip that holds the brake shoes in the caliper. The brakes shoes had worn to the point where the caliper was hitting the metal clip and stopping the brake shoes from compressing on to the rotor so essentially I only had rear brakes. The brake shoes were not worn that much and I've never heard of anyone else having this problem so I don't know why it occurred on my car.
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
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Old 10-19-2009, 02:57 PM
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Join Date: Jul 2009
Posts: 254
Since this thread is 2 years old you may not get a response. After reading the whole thing, I'm inclined to think that the problem either never resurfaced, he got rid of the car, or the final part thrown at it, the vacuum hose, fixed it, otherwise I think the poster would have been back to discuss it further.

IMO, I would have been keen to suspect the vacuum pump/pump lines.

The part I found most ridiculous about the whole thread was that original poster, who was absolutely mortified that his brakes failed and that he might kill someone, was ultimately more concerned about saving a few bucks than saving lives as he rejected the idea of taking it to a dealership to have it expertly diagnosed because it might cost too much.

Incidentally, his scenario about being overcharged for an alignment is likely off base as well because a Mercedes alignment, if done properly (like a specialist would do), requires a few extra steps than the average car. Including being strapped down to put a load on the suspension to simulate the weight of passengers.
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Old 03-05-2017, 06:22 AM
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Join Date: Jul 2014
Location: Cranbourne, Victoria, Australia
Posts: 37
Today, my 3.2L twin cam M104 w201 did the same thing. I was pulling into my driveway at walking pace to park right near my house pillar. About 1m from the pillar, I applied the brakes, the pedal didn't move. Hanging from the steering wheel to gain extra force, I smashed the brake pedal again, planting my back into the seat, I was panicking, I smashed the absolute F@#K out of the brake pedal a third time.... NOTHING... Rock hard...

I crashed into my house at about 3km/h (2mph) almost dead centre into a 90 degree cement corner... Radiator, bumper, grille, AC condensor, and the cross brace between the 2 chassis rails.

It was not like the vac assisit was not connected. It was like a brick was under the pedal.

My nephew came around, the car was fine, then it did it again, this time we were ready with the handbrake.

Earlier, the pedal pulsed liked the ABS was spazzing out, but the car still retarded with pedal application.

So, now, I have to get the car repaired, and I guess, tell the panel shop NOT TO DRIVE IT. Then, get it shipped to my mate's mercedes dealership. He suspects the ABS pump is faulty.
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Old 03-05-2017, 08:39 AM
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Join Date: Dec 2006
Posts: 3,440
Originally Posted by kiqnkf View Post

Earlier, the pedal pulsed liked the ABS was spazzing out, but the car still retarded with pedal application.
I think the vacuum approach described here is a red herring. When the vacuum system fails it takes much more foot pressure to stop the car, but the pedal doesn't feel locked. Hard pedal would more likely be a mechanical failure. In your case, I would suspect an expanded brake hose or sticky caliper. The ABS buzzes because it sees one wheel moving more slowly than another.
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Old 03-13-2017, 02:41 PM
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Join Date: Nov 2008
Location: Goodyear, Arizona
Posts: 161
Exactly the same thing you described just happened to me with my 1995 E320 wagon. I was at a gas station scratching my head when I opened the hood and touched the vacuum line and the coupling in the middle of the line disintegrated.

Remembering a similar situation with my 190E, I went to the store and bought a roll of electrical tape for a $1.29 and rolled it around and around on both ends until it was nice and tight...thereby creating a vacuum. Started her up and voila! instant full braking!

Just got home and the new line is $69.00 at Pelican Parts.

Should take about five minutes to change.

Good luck!
I have never met a man so ignorant that I couldn't learn something from him. -Galileo Galilei, physicist and astronomer (1564-1642)
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Old 03-13-2017, 05:15 PM
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Join Date: Nov 2010
Location: TX
Posts: 3,565
compeltely locked pedal?

of all the vehicles I have put myself in with the worst of the worst designed and maintained systems, never have I had one have a fully locked brake pedal. The only way I think that is possible is to have all the cylinder outlets 100% blocked.

unless there was a lot of corrossion in the system completely clogging the cylinder I cannot think of anything that would lock it up, the ABS pump is also designed to bypass pressure unless called for.
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Old 03-14-2017, 05:58 AM
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Trevor Hadlington
Join Date: May 2014
Location: Worcestershire in England
Posts: 1,190
You will need a vacuum check .The power servo needs vacuum to operate the system .No vacuum , then no assistance = hard pedal .Its like pushing down on the brake pedal without the engine running and you will find it very hard .Try this test ---
Sit in the car .Dont start the engine .Put you foot on the brake pedal and pump it till it get to the floor .Now with your foot on the pedal hold it there , you then start the car .If the servo is good it will lift your foot up as vacuum pressure is building up. Let us know what you find.
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