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Brake problem on 68 Charger RT

grease monkey

Local time
9:28 PM
Jul 16, 2010
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Hello from Luxembourg (Europe)

I have the following problem on my 68 Charger with all four drumbrakes. Ich changed the brake booster because the mecanism inside was rotten. So I replaced the booster and the valve on it with new one's and also changed the master cylinder.
I did a bench bleeding with the master cylinder and after installing all, I did the bleeding on all four brakes. Till there everything alright.
When doing the test on road I have the following problem, the car brakes at first very good with good assistance from the booster, but after a few seconds the boost is gone and the pedal becomes hard, and I can hardly stop the Charger. I did some tests with always the same result. Powerbrake at the beginning and then hard brake pedal and complete loss of brake power.
I checked the underpressure at idling and it was a 15hg which seems to be ok
Where can the problem be ? What shall I do ?

Best regards
kind of sounds like your new booster is faulty, or you have a vacuum leak some where.
Where else than the booster itself can be another leak ?
Brake worked fine before changing the booster