Ok, so I am proficient on replacing brake pads on GM vehicles, although I have not done so in about 10 years. My ML350 with 33k just had the wear sensors come on for the brakes. I am wondering if anyone has replaced these themselves and if so how difficult was the job? Do the new wear sensors come in the pads or do these need to be purchased separately? Do the sensors even need to be replaced when thepads are replaced? Any guidance is greatly appreciated.

 

have a look here

http://audipages.com/Tech_Articles/s...350brakes.html

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Absoutey awsome instructions, thanks a million!

 

Once you get to the point of pushing the piston back in be sure to break the bleed screw open on the caliper. This will insure not to back wash the master cylinder(which can damage it in some instances) and will aid in the ease of pushing the piston in by relieving the pressure at the source.

 

Great advice. I got the new pads and sensor on and re-installed everything. I push the pedal down a few times then took the car for a shprt drive (1 1/2 miles) the pedal continues to feel soft and the braking doesn't seem to be very good. Do you think the new pads just need time to seat against the rotors or does the line need to be bled?

 

As long as the pedal is not going all the way to the floor, you should be OK, you could bleed the lines a bit if you wish, and yes if you did not reface the rotors or put in new ones, it will take a bit to seat in the new pads. I usually do a few hard stops from a moderate speed, but be careful you don't over do it or you could end up glazing the pads. Typically a car always feels different after a brake job, as you were used to the old worn out system.

If you bleed the lines, watch you don't run out of rake fluid in the reservoir, as you could introduce air into the system...

 

I only changed the front pads, rear pads are on order. I have heard two possible causes for the "mushy feel" One- changing front pads but not the rear casues a distortion in amount of fluid or pressure needed to operate the system properly thus casuing the mushy pedal. Two-over returing of the pistons due to them being pushed too far back in the caliper during the removal of the old pads. I pushed the pistions in flush when I removed the old pads as this was the only way I saw to get the new pads back on with sufficient clerarance. I will try to bleed the lines in the morning and see if the fixes the problem but now this over returning theory has me concerned.

 

No, you've just gotten air in the system.

Probably from following the unnecessary (not in WIS) suggestion of opening the bleeder valve.

 

Once you push the piston in with the hose on the valve and then close the valve theres really no way air can get in there. I was just including my recommendation to be added to those instructions that were in the link. I posted the reason for breaking open the bleed screw upon pushing the piston back in. I am an ASE certified Under Car Specialist and worked in a Midas shop for years and years before working for Mercedes.

 

Thanks to all who responded with help and advice. I did replace the brakes myself and had the lines bled by a shop (didn't feel like buying a self bleeder or asking my wife to help). The pedal still feels soft and goes down much further than before but the car stops well and doesn't seem to be any worse in the braking distance than with the factory pads.

Again, thanks to everyone for your advice and suggestions, I really appreciated it.