Newly installed SA - Excessive pedal play and poor performance

[JCM1]

Hi All:
Just had front brakes replaced with used SA calipers and new rotors on my 1992 500e Euro along with new LCAs. I left the rear brakes and calipers stock. Much to my dismay I now find the braking to be worse than before. There is excessive pedal movement ~ 3/4 of total travel and braking is poor. I have to pump the pedal and even in doing this the car barely stops.

I did not have this condition with the old brakes. Is this a symptom of the master cylinder seals going? I had read that the master cylinder is sufficiently large to accommodate the SA larger caliper but given the poor performance maybe that's the fix.

Any help with diagnostics or suggestions appreciated!


All the best,

Joe

[alabbasi]

Might still have air in the system

[doolar]

Air in the system would be the first thing I'd check. If you have a pocket left in one or both of the calipers you will experience what you do. Bleed, bleed, bleed and bleed some more. I think I went through two litres worth of brake fluid when I did this work, both front and rear.

When I swapped to the SA kit I had a totally opposite experience. I used the original master cylinder, and my brakes where notably better from the start.

[gsxr]

It sounds like the system is not properly bled. Did you use a pressure bleeder with 2 bar / 30psi of pressure, and after bleeding all 4 calipers also bleed port SP with the engine running? If so, it COULD be the MC seals... but I'd bleed again (pull at least 150cc from each caliper, doesn't hurt to use more) before condemning other components. What you describe is something with the hydraulic system, not the calipers themselves.

Pedal travel should be very similar to stock brakes, most people probably would never notice a difference (assuming similar pad compounds).

[JCM1]

Might still have air in the system

Thanks! Yes I thought so but was assured that system was bleed. Will re-bleed.

Air in the system would be the first thing I'd check. If you have a pocket left in one or both of the calipers you will experience what you do. Bleed, bleed, bleed and bleed some more. I think I went through two litres worth of brake fluid when I did this work, both front and rear.

When I swapped to the SA kit I had a totally opposite experience. I used the original master cylinder, and my brakes where notably better from the start.

Thanks, I will re-bleed!

It sounds like the system is not properly bled. Did you use a pressure bleeder with 2 bar / 30psi of pressure, and after bleeding all 4 calipers also bleed port SP with the engine running? If so, it COULD be the MC seals... but I'd bleed again (pull at least 150cc from each caliper, doesn't hurt to use more) before condemning other components. What you describe is something with the hydraulic system, not the calipers themselves.

Pedal travel should be very similar to stock brakes, most people probably would never notice a difference (assuming similar pad compounds).

Thanks GSRX ! Not sure if the rears were bleed as only changed the front calipers. I'll do then too. BTW, what is SP and where is it located? Why does this need to be done with the engine running?

All the best,

Joe

[gsxr]

Joe, it's part of the factory procedure for ASR. The start of the procedure involves releasing pressure from the SP port, then bleeding all 4 calipers, and finally starting the engine and bleeding SP port. You definitely need to bleed all 4 calipers and the SP port to get the system working correctly.

Link to FSM procedure, see page 2 / section B:
http://w124-zone.com/downloads/MB%20...94_95/4280.pdf

[JCM1]

Thanks GSRX! I'll check to see if the mechanic used this procedure and if not I'll get it done.

All the best,

Joe

[gsxr]

Joe, also double-check that your mechanic is pressure bleeding, and not pumping the pedal.

ASR cars are not happy unless they are pressure bled per factory procedure.

[alabbasi]

My 560SEC has ASR and was a giant pain in the rear to bleed

[captruff]

After I installed my rebuilt SA calipers, I re bleed the system 3 additional times at 500, 1000, and again at 1,500 miles....brake fluid is not that expensive and bleeding brake is fairly easy. +1 on air in system

Jeff

[Rouven036]

+2 on air in the system.

[gerryvz]

Any update on this? Did re-bleeding solve the issue?