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Old 02-03-2010, 10:49 PM   #1
70Custom10Nut
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Question brake question

OK, I've replaced everything(power drums all around). shoes, cylinders, and even the booster. The only thing I didn't replace yet is the master cylinder. My problem is that even with all the air bled out the brake pedal sinks to the floor while I sit at a traffic light. Would a bad MC cause this? The system doesn't leak anywhere. The truck stop well, but as I sit at an idle the pedal sinks to the floor. Can anyone enlighten me? thanks, Cnut
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Old 02-03-2010, 11:00 PM   #2
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Re: brake question

100%. Don't rebuild it. Just get a new one. The fluid is bleeding past the piston. I bet you $100 it fixes it. Anybody wanna take me on this????
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Old 02-03-2010, 11:02 PM   #3
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Re: brake question

vaccum leak or bad seals in the mc? can someone listen under the hood in the drive way while you press the brake?
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Old 02-03-2010, 11:05 PM   #4
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Re: brake question

The only way a MC will bleed down is a hydraulic failure.
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-Slammed and Tubbed
1955 Cameo
-Straight six, Turbo Hydro option
1955 BelAir 2 door post
-All original down to the oil bath air cleaner
1964 Corvette
-All power A/C 327 4 spd. tanker

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Old 02-03-2010, 11:06 PM   #5
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Re: brake question

A vacuum leak would cause the brake pedal to be hard.
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1970 Short/Fleet C-10 (Project)
-Slammed and Tubbed
1955 Cameo
-Straight six, Turbo Hydro option
1955 BelAir 2 door post
-All original down to the oil bath air cleaner
1964 Corvette
-All power A/C 327 4 spd. tanker

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Old 02-04-2010, 12:24 AM   #6
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Thumbs up Re: brake question

Quote:
Originally Posted by BOOB View Post
100%. Don't rebuild it. Just get a new one. The fluid is bleeding past the piston. I bet you $100 it fixes it. Anybody wanna take me on this????
No bet
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Old 02-04-2010, 12:30 AM   #7
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Re: brake question

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No bet
Awwwwww....COME ON!!!!
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-Slammed and Tubbed
1955 Cameo
-Straight six, Turbo Hydro option
1955 BelAir 2 door post
-All original down to the oil bath air cleaner
1964 Corvette
-All power A/C 327 4 spd. tanker

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Old 02-04-2010, 02:48 AM   #8
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Re: brake question

I had the same problem. It's your master cylinder. The master cylinder on these trucks are cheap.
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Old 02-04-2010, 03:09 AM   #9
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Re: brake question

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100%. Don't rebuild it. Just get a new one. The fluid is bleeding past the piston. I bet you $100 it fixes it. Anybody wanna take me on this????
Yea Ill take you on that one My bet is that you are right on, but it could also be a small leak in the system anywhere else it has been apart crazyL
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Old 02-04-2010, 08:02 AM   #10
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Re: brake question

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Yea Ill take you on that one My bet is that you are right on, but it could also be a small leak in the system anywhere else it has been apart crazyL
Naaaaaah....this guy knows what he's doing!
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1970 Short/Fleet C-10 (Project)
-Slammed and Tubbed
1955 Cameo
-Straight six, Turbo Hydro option
1955 BelAir 2 door post
-All original down to the oil bath air cleaner
1964 Corvette
-All power A/C 327 4 spd. tanker

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Old 02-04-2010, 08:11 AM   #11
67ChevyRedneck
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Re: brake question

If your pedal goes to the floor, then something is leaking. When the MC goes bad, you can sometimes see fluid up under the dash, dripping off of the rod that goes into the MC from the brake pedal. They're not that expensive, if you're sure everything else is good, it's probably the MC.
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Old 02-04-2010, 11:40 PM   #12
70Custom10Nut
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Re: brake question

Thanks to all. It was the MC for sure. $15.00. Now all I have to do now is readjust my rod to the original length (I turned it out to compensate for the bad MC, live and learn). Also put a new Edelbrock Carb on too (Oh, Happy days!!! Did I ever say my wife really loves me?), now the ol' girl runs like a scalded hog! Cnut
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Old 02-05-2010, 10:35 PM   #13
glider_6969
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Re: brake question

I think it's unanimuous ,, get a new mc. I just replaced mine. Remember to bleed it before you mount it on the truck.
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Old 02-06-2010, 10:08 AM   #14
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Re: brake question

I agree with glider 6969, Just replaced my mc, had the same problem. bench bleeding the mc is a must.
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