I tried to post this question earlier today but it never came up? I must have done something wrong, I'll try again. I just bought my son a 93 190e 2.3. It needed brakes all the way around. I replaced the discs and pads on all four corners. When I got done, I have very little peddle and stopping power! I hadn't opened the hydraulic system but I've gone ahead and bled the brakes with no success. I then removed the master cylinder and found nothing wrong with it also. After the fact I picked up the CD repair manual and it stated that the ABS unit should be bled. My ABS unit doesn't look like the picture in the manual, and has no "sp" bleeder screw? My question is, have I messed up something in the ABS unit when I pushed the pistons in the calipers while fitting the new pads? Has anyone ever had this problem? and why is my ABS unit not like the one in the manual? My son sure likes this car, but would like it more if he could drive it. Any help will be appreciated as I'm not looking forward to a 70 mile tow to the closest dealer. Thanks!

Start by dumping all fluid from reservoir. Use fresh fluid & fill reservoir to the top of the filler neck, many times the rear section of the reservoir will develop an air pocket(very hard to see)& then no front brakes. Open all 4 bleeders & allow to gravity bleed for 10-20 minutes. Always making sure that the reservoir is FULL, then try pressure bleeding. Good luck!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

M.B.Doc
Thanks for the advice, but I've not only tried gravity bleeding but pressure bleeding with the car running and with the car not running, also with a pump type bleeder. All after reinstalling the master cyl. and adding new fluid. All the advise I keep getting centers around fluid and the master cylinder, I'm a little confused how changing the pads could have affected these items when I had a good peddle before???

Very common for air pocket in the VERY back section of reservoir. Try OVERFILLING the reservoir & allow time for it to fill that section of reservoir. This happens to even very good dealership techs. The line closest to the booster is for the front. NEVER push old fluid back into system on ABS cars! Always open bleeder w/pushing pistons back into caliper. When you bleed system do you get good fluid flow??

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

I have had the problem you discribe but for me it was a simple pannel by the brake came lose and would not let the pedal go down. Hope thats all it is for you.

M.B.DOC
Thanks for your help so far! As far as the back chamber in the master cyl., I did run it out the first time I bled the brakes and learned to overfill to fill it. I've also learned to pinch the brake lines and open the bleeders when pressing the caliper pistons in! But I can't back up so what do I do now? Do you think that I have damaged something in the ABS? Can it be rebuilt or disassembled and cleaned? Would it do any good to run a can or two of fluid through the system to make sure there is no air and to flush out any dirt? I can't help but think that the ABS unit needs to be bled but my ABS unit looks nothing like the one in the CD manual and has no bleeder? Any help will most appreciated!
Thanks, Marc

The ABS solenoids are in a rest position(allowing fluid flow) unless activated. Unless dirt in the fluid was pushed into the valves I don't think that could be the problem.
Durning gravity do you get a good flow of fluid? Running fresh fluid through the system was one of my first suggestions. When you pump brakes is there the same pressure at bleeder on caliper as there is at master cylinder lines?

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

I haven't gravity bled the system since the problem first started. At that time I was able to get a trickle at all four corners, but I'm not sure you would call that good flow. Should I re-bleed the system with the gravity method? I'm not sure I understand your next question, bear with me! Are you suggesting removing the pressure line before it enters the ABS unit to compare fluid flow under pressure between this point vs. at a wheel cyl.? If that is your thought I'll give it a try later today, let me know and THANKS!

With the system closed, pump the pedal until some pressure is there. Then crack brake line at the master cylinder one at a time to see if the mstr. cylinder in making any pressure! If you can't build any pressure then master cylinder is done!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator