the brakes from hell!!! help me please...

[benzforlife]

these damned brakes have given me nothing but hell on this car!
-took the car in for new front rotors and pads.
-car comes out with a mushy brake pedal, take back in a week later
-mech. has bleed the brakes a bunch of times, put on 2 new master cylinders
-now brakes are worse then before, i cant even lock up the wheels with the pedal
-im stumped, hes stumped....

Any opinions?
thanks

[lietuviai]

Find another mechanic.

[Hit Man X]

Originally Posted by lietuviai

Find another mechanic.

LOL, beat me to it.

or... gasp... learn to work on your own car!

[kerry]

It's really hard to know what advice to give since we don't know what exactly the mechanic has done. Mushy pedal is typically a symptom of air in the lines somewhere. Did the mechanic bench bleed the master cylinders? How did he go about bleeding the system?

[benzforlife]

no dont get me wrong he is a really great mechanic. he says that never in his life has he had a cars brakes be more difficult!
Theres no leaks anywhere, everything has been bled and properly installed.
He says hes going to try a few things tomorow.
But what are some of the things that it could be?
by the way the brake booster is absolutly fine to...

[Cervan]

air compresses, hydraulic fluid doesnt. so if you have air in your lines you will have a mushy pedal. tell him to bleed the brakes slowly and carefully this time but bleed it with the bucket method, (get a clean bucket fill it with about a liter of brake fluid and then stick a line on the bleeder valve and into the bucket submerged, this will make sure no air is able to get back into the system.) if this doesnt work, something is wrong such as a leaking brake caliper or something of the sort.

[lietuviai]

I'd just use a clean clear bottle of some kind. That's what I always use when bleeding my brakes. I can see when the bubbles stop coming out of the hose during the bleeding process.
Also start with the wheel farthest from the master cylinder and work toward the next farthest until you've reached the last wheel.

[benzforlife]

Originally Posted by Cervan

air compresses, hydraulic fluid doesnt. so if you have air in your lines you will have a mushy pedal. tell him to bleed the brakes slowly and carefully this time but bleed it with the bucket method, (get a clean bucket fill it with about a liter of brake fluid and then stick a line on the bleeder valve and into the bucket submerged, this will make sure no air is able to get back into the system.) if this doesnt work, something is wrong such as a leaking brake caliper or something of the sort.

thats pretty much what he was doing. i also had my leking calipers replaced

[pawoSD]

When I bled the brakes on our 300D before we put it on the road recently....I found there was a TON of air in the lines to the rear brakes....braking power increased significantly when I finished bleeding all the lines....no other brake work was done, just new fluid/a good bleeding.

[vstech]

tell him to either get a power bleeder to pressurize the MC and eliminate all air in the system while bleeding, or just open each bleeder while someone keeps the MC full and let the fluid flow out gravity style until it's clear of bubbles. If fluid does not flow out one of the calipers bleed screws, you have found the problem.
the brake system on this car is the simplest and best ever! you may have a bad flex line on one of your calipers, also you may have a bad o-ring on the MC allowing air and fluid into the system.

[gsxr]

I agree with John. You need to bleed the brakes with a pressurized bleeder, usually 15-20psi is adequate. That should cure the spongy pedal.

Since the tires won't lock up, I would also check the pads for contamination (oil, grease, etc). That sounds like possibly a friction level issue, unless the hydraulics are so soft that it's affecting braking pressure...

[benzforlife]

yeah the brakes are all new, the rreason they wont lock up is because there not enough pressure.
he told me that he has never in his life dlet with brake brake system being so dam earetable

[CarreraDan]

I don't understand how a mechanic can be having problems with the brake system as easy and simple as the Mercedes. I redid the entire system (lines, pads, rotors, m/c,) on my 123 and used a power bleeder (Motive) that I use on my other German car and had a rock hard pedal. I was very suprised when I redid the brakes at how well they stop the car--not hand of God like the 911 but very well for how much the car weighs. I think I would find another mechanic or learn to do it yourself as you know the old saying "if you want something done right do it yourself."

[biobenz240d]

On an old Ford I had about 20 yrs ago, I had the same problem. Found out that it was the flexible brake line . When you step on the brake the line would blow up like a balloon, with no pressure in it it looked normal.
I always use a power bleeder and bleed from the wheel to the master cylinder. This will even take care of air left from not bench bleeding the master cylinder correctly

[vstech]

see post #10 http://www.peachparts.com/shopforum/showpost.php?p=1606213&postcount=10