First I have a 70 dart custom that I just got, on the way home with it a brake hard line ruptured, a quick trip to a friends shop fixed that. Since then every now and again while sitting at a light the pedal would loose pressure and sink to the floor so I bled the brakes thinking the problem was just air in the system. Now if I hit the pedal hard it holds pressure just fine but if I let up just a little it looses all pressure and sinks to the floor, also if I slowly easily hit the pedal it'll go right to the floor, so now I'm thinking master cylinder? Any other ideas? Any help would be greatly appreciated. Thanks, Dave

I'd look real hard at the master cylinder, then at all of the lines and wheel cylinders for any signs of leakage. Make sure you look under the carpet around the master cylinder / pedal area.

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

sorry, I should of mentioned that, there's no apparent fluid leak, master cylinder level isn't going down at all

Your symptoms are right on for internal master cylinder leakage.

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Joshua

Yes... Master Cylinder is bad. I had EXACTLY the same symptom, sinking pedal at stoplight, solved it with a master cylinder replacement.

BTW - It took my two tries to get a good rebuilt master from the auto parts store. The first one did the same thing as the bad one.

-Mac

Yup, bad master cylinder.

Don't drive it in this condition unless you want to cause a rear-ender, and a big law suit.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

or you get get at pumpin the brakes, i drove my valiant wit a crap MC for a few months... no dings

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'72 Valiant DD for over a decade-225-Disc brakes, big T-bars, big Sway bars f/r, carter bbd/super six, GM HEI, 2- 12" subs in trunk, 1000w amp...
'77 cherokee cheif widetrack-360-33x12.5 tires-no lift. keeps driveway dry-project/backup DD/mudder

The best thing to do is just set the car on fire?

Just kidding! Hi Dave! Good luck at the parts counter this week.

(Dave is my buddy and a hardcore chebby refugee!)

radar

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madam im adam

if we set my car on fire we can use the air filter for your demon, that'll fix it, right?

Thanks guys, I figured it was the master but wanted another opinion just to be sure. I guess it's off to advance after work tomorrrow