Almost no brakes

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Mikes270dart

Mikes270dart

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New to me 1971 Duster 340 4 spd. Car supposedly has power disk brakes. When trying to stop press the brake pedal it moves small amount and stops, but the car doesnt. Press as hard as you can and it will eventually stop. Lots of vacuum at the booster. When you start the car with your foot on the brakes it does not move. Don't know how to post the video you can see how little the travel of the pivot is. If you look at the pick you can see how close the the pivot is to the back of the booster. Is this normal. I think I'm not getting full pedal travel but unsure of how to increase it.

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If it hasn't been done already I'd flush and refill the system first.
 
When you apply the brakes driving, does the engine try to die or idle down lower that it should? If you get in the car, not running, press you foot on the brake pedal and start the car, does the pedal move down? Where is the vacuum line hooked up at on the engine? Did you test the check vavle and its seal? How much vacuum does your 340 make at warm idle?
 
The pedal should drop when started with your foot on it to indicate the booster is applying vacuum. Either the booster is bad, or the booster check valve is bad.
 
Look, this is real simple. The hydraulics are working or you'd have no pedal and it would not stop at all. This is a vacuum issue, whether the check valve is bad or the booster is bad. It's really that simple.
 
Mikes270dart said:
Valve is good. Should I try and rebuild or replace.
Click to expand...
Ok, so then you've unplugged the valve from the booster with it running and confirmed vacuum at the end of the valve that installs in the booster? Then do this too. Start it up with everything connected. Let it idle a minute or three. Now cut it off and pull the valve hose and all out of the booster. You should get a rush of air entering the booster. If not, you just confirmed a bad booster.
 
Mikes270dart said:
Followed your instructions. No air escaped. Thanks
Click to expand...
But BEFORE you do that, did you actually TEST the check valve, or just see if it was pulling vacuum through it? If the check valve is bad, when you cut the car off, you immediately lose the vacuum that's normally stored because the booster is open to the engine's intact tract. I would CONFIRM that the check valve is good FIRST if you have not done that 100%.
 
Bought this booster from a well known mopar parts dealer and this is what came. Does this look right. The end that attaches to the brake pedal is not what I was expecting.

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