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1982 300D-Turbo
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209 Posts
Discussion Starter #1
So I replaced the Master Cylinder AND then this weekend the Brake Booster (guide coming soon) and now I can certainly slam on the brakes and lay down some smoke if need be (before I had the hardest time pressing on the brake - no brake booster). However, before when I pressed on the brake about 1 or 2 inches, I stopped quick and firm. Now I have to almost put the brake petal to the floor to get the same amount of stoppage. Inotherwords, it's like I have to press 6-8" where I used to only have to press 1-2" to get the same stopping power.

What did I do wrong when I replaced the Brake Booster? Brand New o-ring, and gasket. All went smoothly.

Or maybe I just need to bleed the brakes again? Thoughts?
 

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1982 300D Turbodiesel 212K or so, it doesn't work anymore :-)
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216 Posts
you either have air in the lines *most likely situation* or have a leak somewhere...classic issue that's easy to fix but can be a PITA...

good luck!
 

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1984 300D
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5,070 Posts
The leak could be inside of a faulty rebuilt Master Cylinder. It is a common problem.

Re-bleed the Master Cylinder First then bleed the rest of the Brakes.

I recieved a rebuilt Master Cylinder that had a problem of slighly sinking pedal. I kept it because I had to get the Car on the road and I also thought I might not have bled the system well.

Later 3 attempts at bleeding did not change anything. I got a total of 1.5 years use out of that Master Cylinder and the Pedal went to the Floor with nearly no Brakes.
At the time I could not find the paper work to exchange the Master Cylinder so I bought a brand new one made by FENCO (Taiwan). And for 2 years now it has been perfect.

A month after replacing the Master Cylinder I found the paperwork and under the life time warranty exchange the Rebuilt Master Cylinder for another Master Cylinder. So I guess I have an extra as a back up; assuming that one works.
 

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W-1-2-3 Go!
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16,161 Posts
Speaking of MC's, what brand is recommended?

I'm curious if the Wagner rebuilt installed on mine is good quality or if I should start looking for another one soon.
 

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It seems a LOT of people are having trouble with rebuilt master cylinders. H-Town-Benzo-Boy was having problems with his rebuilt Cardone MC. Once he replaced it with a NEW ATE master cylinder all was well.

A new ATE (OEM) master cylinder is only $88 at Autohaus. I don't see why anyone should buy rebuilt, the price difference isn't that much. Some things are just not worth buying rebuilt.
 

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2013 MINI Copper S Clubman, '84 300CD-weekend car
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10,152 Posts
^ I just installed one of those, we'll see how long it lasts.

I'm guessing, quite a while.
 

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1984 300D
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5,070 Posts
It seems a LOT of people are having trouble with rebuilt master cylinders. H-Town-Benzo-Boy was having problems with his rebuilt Cardone MC. Once he replaced it with a NEW ATE master cylinder all was well.

A new ATE (OEM) master cylinder is only $88 at Autohaus. I don't see why anyone should buy rebuilt, the price difference isn't that much. Some things are just not worth buying rebuilt.
Concerning the above in red; my failed rebuilt Master Cylinder was also a Cardone one.

However, my Cardone Rebuilt Rear Axles have been fine as well as other rebuilt items I have used by Cardone.

I believe the rebuilt Master Cylinder issues are being caused by the corroded pitted spots that are often at the bottom of the Master Cylinder. Evidently the rebuilders are just cleaning the Master Cylinder Body and sticking in new guts/parts.

In the old days they used to hone out the pits and install new over sized parts; or you sometimes would find one that was sleeved back to standard.

With Mercedes the available pool of good rebuildable cores may be so small compared to say Chevy Master Cylinder cores that they are attempting to use the marginal cores and hoping you will lose the receipt or sell your Car before it goes bad.
A good rebuilt Master Cylinder should last at least 5 years.

I do not know how long a New Master Cylinder should last because the New one I put on (FENC) is the first new on I have ever installed.
Until my Mercedes since 1968 I have either rebuilt the Master Cylinder myself or installed rebuilt Master Cylinders.
 
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