[W126 Coupe] would anybody be interested in big brakes?

[Steve Nervig]

On Apr 19, 2005, at 7:41 PM, Shayegan, Richard wrote:

> -----Original Message-----
> From: mbcoupes-bounces at mbcoupes.com
> [mailto:mbcoupes-bounces at mbcoupes.com] On Behalf Of Dan Landiss
>
>> It is my understanding that the ABS module CANNOT be properly bled
>> without a positive pressure unit pushing from the master cylinder end.
>> Can anyone confirm?
>
> According to the service manual if you don't have ASR you can do it 
> just
> by pumping the brake pedal. A non-Benz mechanic I know says if you keep
> the system full (i.e. just flush a lot of fluid thru rather than drain
> most of the fluid then flush it) then you don't even need to do that.
> Richard
>

Contrary to what the 126 manual may say, with ABS you must use a 
pressure brake bleeder or it will be nearly impossible to correctly 
bleed the system through all of the ABS circuits. I think MB learned 
that this is the case because all of the post-126 manuals call out for 
2 bar (approx 30psi) of pressure when bleeding ABS systems.

Richard, you have been getting good advice here. I was very specific 
when I said, "Replace the hoses, put stock OEM (like Textar) pads on, 
flush the system, restore with fresh Dot 4+ fluid, and pressure bleed."

Don't try to inspect those 19 year old hoses, to try to think they 
might still be good. They will NOT be. Replace them.

Put stock pads on. You have stock rotors; those PBR Metalmasters will 
not give you a good stop when cold (from what I've read). I have heard 
good things about them when warm. But your next panic stop (like your 
accident), will come when your brakes are cold. The OEM Textars (and 
Jurid?) where designed for your car and work Very Well.

Flush the system and put fresh fluid in. MB recommends EVERY year; some 
say every 2 years is enough. Brake fluid absorbs water; water corrodes 
and boils - not good.

Pressure bleed. If you or your mechanic did not pressure bleed, all the 
old fluid did not get out. Repeat, it did not get out. If you bleed by 
the pedal method, it will not properly bleed the ABS system. In 
addition, by using the pedal, you run the very real risk of damaging 
the master cylinder piston seal, when it goes beyond its normal travel 
(where there will be a ridge).

Once you have done the above four things, let us know how the brakes 
work. There may still be problems, but you will have now eliminated the 
common problems and will now have a baseline from which to pinpoint 
additional work necessary. Some may say that #2 (change to OEM brake 
pads) may not be necessary, or recommend some other fancy pad. I will 
concede this, but still urge their replacement, if the current pads are 
near their end of life.

Without doing the above things, we will not know where your soft pedal 
is coming from (if it still exists).

Regards,
Steve