Ok I replaced my Master Cylinder OK the problem I have now is the brake pedal no longer travels to the floor but the pedal seems harder than before and now I have to choke it to turn it off. I checked vacuum lines that i could see under the hood is there a diagram or something I could use? and also just in case you say it is the booster what is the vacuum pressure suppose to be if i get a tester?

Thanks,


I still Love my Benz!!!

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1st time Mercedes Owner.
1980 300D 123/130
what do ya expect for $600.00
Needs TLC

Did you replace the 0-ring between the booster and master cylinder? I'm betting you have a leak between the two somewhere. All the symptoms point to it. 18-21 inches of mercury or thereabouts I think.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I agree, I bet you forgot the rubber gasket between the M/C and the booster (or didn't realize there was one....I didn't the first time either)

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I'd agree. No shutoff and hard brake pedal = vac leak. Agreed about 20 inches of vacuum. When something like this happens to me, I think back.. What was the last thing I did? That's probably where the problem lies.

There's an O ring????? Was it suppose to come with the MC? or do you have to get it separate? That makes sense. You Guys are AWESOME! can someone point me in the right direction to fix? This was my first MC i changed with out the guidance of my Big Brother or Uncle


Now please tell me I do not have to drain the fluid again and bench bleed it. can I just unbolt the MC and put the o ring in?

__________________
1st time Mercedes Owner.
1980 300D 123/130
what do ya expect for $600.00
Needs TLC

Yup- unbolt it, slide forwards and install o ring.
I bought 2.

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1984 123.193 372,xxx miles, room for Seven.

1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven.

Ok i took it out now where does the O ring go? on the pin coming out of the booster? or inside the MC?

__________________
1st time Mercedes Owner.
1980 300D 123/130
what do ya expect for $600.00
Needs TLC

Can someone send a pik of this o-ring?

P E H

Should be a "channel" around the large opening after you separate the MC from the booster. No need to re-bleed, just be careful to not damage the hard brake lines, there is enough room.
May be able to get a pick, will have to wait.

__________________
83 SD

84 CD

The o-ring goes between the booster and the m/c. It slips over the end of the master cyl.

__________________
80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)

looking at the pic, assuming this is the same mc you bought, where would the oring go?

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
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1987 190D 2.5Turbo
1987 190D 2.5Turbo
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1987 300TD
1987 300TD
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I would think it would cover up the unpainted area just in front of the mounting holes , fitting in that smaller "L" shaped groove there.

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80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)

Took pics, the ring sets in a channel on the MC, and "nestles" into to booster.
Hope this helps.

Attached Thumbnails

   

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83 SD

84 CD

Toomany,

Yes it helps. I recently replaced a master cylinder (MC) and I was worried I didn't put the o-ring in place. But I installed a used MC so the o-ring would have already been on the replacement MC.

P E H