All of a sudden soft brakes with no fluid loss... - Page 2 - Mercedes-Benz Forum
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#11 (permalink) Old 01-11-2011, 12:25 PM
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ok another quick update...we bled the brakes just didn't feel right. I guessed that since the vehicle had no vacuum, the brakes wouldn't ever feel right. My mityvac just wouldn't get the job done so I feared no other way to test the booster than to crank 'er up.

cranked up the car *need to get those injectors rebuilt btw* and the brakes return to basically normal. Mash the brakes and you get decent braking and they get stiffer and stiffer upon each time you step on it; requiring less effort to fully engage the brakes.

My question now is: Does this sound right? Should the car's brakes get stiffer the omre times you pump the brake while running? The benz is only the second car where i've worked on the brakes and the first one completely by myself. I don't have the intuition for it as the practical experience just isn't there yet.

Also, should i try to bleed the brakes with the car running? It's cold out but i just don't care; I need my car back!
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#12 (permalink) Old 01-11-2011, 12:40 PM
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Sounds like you're there, drive it!
It's normal to have a hard peddle without the vacuum assist, and yes the more you pump the harder it will get.


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#13 (permalink) Old 01-11-2011, 12:43 PM
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When the car is running and you pump the brakes, the booster uses up whatever available vacuum assist the vacuum pump (on a diesel) can provide. So yes, the brakes get stiffer. Then when you stop pumping, with foot firmly on the brake pedal, the pedal should lower a little when available vacuum is sufficient to provide vacuum or booster assist.

Since you're idling when you performed this test, the available vacuum won't replenish quickly.

Try this: pump on the brakes when the car is OFF. Then with your foot firmly pressing on the brake pedal, turn the engine on. The brake pedal should lower due to available vacuum or booster assist, and you should feel the "normal" brake pedal feel.

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#14 (permalink) Old 01-11-2011, 02:09 PM
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Thanks for the words guys, feels like i got it. It was apparently just a bad case of air in the lines. According to what you guys said, it sounds like things are in order.

Warmer weather will bring a brake system flush, new pads and resurfaced rotors; I just wanna make it that long!

Thanks again to the community!
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#15 (permalink) Old 01-12-2011, 08:42 AM
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Pumping fast make bubbles or rather it breaks them up into smaller ones. Makes it really hard to bleed them all out. It may have very well been that you had a bubble at the rear say that finally moved up. I strongly recommend getting one of the one man bleeders so you dont have to open and close.


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#16 (permalink) Old 01-16-2011, 03:08 PM
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Want to thank ya'll for all the advice/help again.

Another question on the topic. I went ahead and replaced the pads on the car today. The fronts looked like they had a lot of life left while the rear were really worn down. What are the chances that my front calipers are locked up and I'm only braking with the rear of the car?

The car stops ok, but I don't think she stops like she is supposed to.

Any guesses?
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#17 (permalink) Old 01-16-2011, 04:24 PM
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If your fronts were locked up, you would not have been able to install the new pads
Since the rears only do about 30% of the braking, they usually last at least two to one, they were probably
not changed the last time the fronts were. At this stage of its life, You may never change them again



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#18 (permalink) Old 01-16-2011, 05:49 PM
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Rotors and pads should be changed together.


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#19 (permalink) Old 01-17-2011, 09:53 AM
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oh they'll definitely get changed again. I picked up a set of rotors off CL for 10 bucks a piece. She'll get new bearings, SS braided lines, probably a new MC, brake booster, and pads over the summer.

I had a set from my dads car...when he bought his it had a set in the trunk. His mechanic told him they weren't the correct ones. He got us on that one!
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#20 (permalink) Old 01-17-2011, 11:12 AM
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oh they'll definitely get changed again. I picked up a set of rotors off CL for 10 bucks a piece. She'll get new bearings, SS braided lines, probably a new MC, brake booster, and pads over the summer.

I had a set from my dads car...when he bought his it had a set in the trunk. His mechanic told him they weren't the correct ones. He got us on that one!
NEW ones aren't that much more expensive over these CL units. I just hope they're NEW and unused w/o any warping.

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