Reman vs New Brake Master Cylinder? - Page 2 - PeachParts Mercedes-Benz Forum

JamesDean · #16 01-19-2011, 11:51 PM

mak, when you say front pipes..you mean the soft rubber lines or the hard metal ones?

MBeige · #17 01-20-2011, 01:00 AM

I'm not sure if master cylinders are "paired" to certain types of calipers. Since you've upgraded yours, it might be possible that the upgraded calipers require a beefier type of MC and would (might) prematurely wear yours out.

Just tossing this idea out there.

punkinfair · #18 01-20-2011, 01:11 AM

master cylinder should be about 190.00 retail, that's for a genuine ATE brand master. might get it for less but just make sure it's ATE brand and it will be exactly the same as the one from the dealer.

Hirnbeiss · #19 01-20-2011, 11:31 AM

Sponginess alone is usually not caused by a bad master cylinder. If you don't have visible leakage caused by deteriorating grommets or corroded fittings, the other failure mode would be leaking piston seals due to wear or corrosion. This will cause fluid to leak back into the reservoir, and you will notice that your pedal continues to sink to the floor to compensate.
Sponginess = gas in the fluid or elasticity in the brake lines
Sinkiness (yes, approved King Julien word) = fluid leakage around internal seals or out of fittings.

JamesDean · #20 01-20-2011, 11:37 AM

LOL King Julien.

I've got a replacement set of brake lines coming and a liter of typ 200. I'll replace them and bleed the system.

We'll see what that does, if I still have sinkiness, perhaps some replacement calipers are in order.

JamesDean · #21 02-17-2011, 02:06 AM

Alright. I replaced the lines, no real differences.

I replaced the master cylinder, bled the system with a power bleeder, I opened each bleeder for like 30 seconds to get all the air out...still feels soft. Like I dont get any REAL breaking power until I hit 3/4 pedal travel..

When I got the old master out, I squeezed the piston on it and fluid shot out of the side port, but nothing from the top port...is that a return? or does that indicate that its bad?

Whats next on this list? Could the calipers be bad?

Stretch · #22 02-17-2011, 03:07 AM

Quote:

Originally Posted by JamesDean

Alright. I replaced the lines, no real differences.

I replaced the master cylinder, bled the system with a power bleeder, I opened each bleeder for like 30 seconds to get all the air out...still feels soft. Like I dont get any REAL breaking power until I hit 3/4 pedal travel..

When I got the old master out, I squeezed the piston on it and fluid shot out of the side port, but nothing from the top port...is that a return? or does that indicate that its bad?

Whats next on this list? Could the calipers be bad?

On my W123 I often need to bleed a bit longer than 30 seconds to get the air out... it isn't really a time thing - it is more of a stubborn bubbles still coming out thing.

If I were you I'd give the system another bleed - if you still see bubbles - keep going!

Another trick - just in case you are still busy welding - is to wedge the brake pedal down for a night or two or three! I read this tip on this forum but I've forgotten who posted it originally - so credit goes to ???? - still if this makes even a slight difference then you know it is air in the system.

As for the calipers you can check them out by pushing the pistons back in - catch fluid that pops back out of the MC with rags (it has to go somewhere) - and then get someone else to apply the brakes whilst you watch the piston travel. They should be fairly smooth. Sometimes it is difficult to see this on a car - you can test this with the calipers removed from the car but you need stop the pistons from popping out with an appropriate sized block of wood (for example).

Hirnbeiss · #23 02-17-2011, 06:16 AM

You did bleed the MC thoroughly first?

JamesDean · #24 02-17-2011, 10:44 PM

I didn't do anything special to the MC. I had searched on here and the general consensus seemed that I could power bleed it after it was installed and be OK.

I did notice the follow:
-On long highway cruises, stopping at the off ramp, the pedal felt pretty good on the first press
-Leaving this morning after setting up Army's leave-the-pedal-engaged overnight trick seemed to improve the pedal for the first few pumps.

I have no external leaks. It could be an internal seal issue on the calipers, I'm not sure how their internals are laid out and what could "go bad"...

I'll give it another bleed in a few days.