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Old 04-14-2010, 12:09 PM
ronald467
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Default Brake pedal firm when engine not running..goes to floor when running!

I have a nice firm brake pedal when the car is not running, as soon as I start the engine, the pedal goes almost to floor.

So I ruled out the master cylinder, since I just replaced it last week. I bled the brakes and the master cylinder at least 10 times.

The diagnostic check on the brake booster appears normal, except that when I start the engine with my foot on the brake, the pedal goes almost to the floor with a very mushy pedal.

Can somebody shed some light on this problem? The brake booster holds vacuum just fine so again I am lost. What could this problem be?

Anyone have any ideas?

99 Nissan Frontier 4x4 (ABS bypassed) V6 - New Calipers, New pads, new brake lines, factory rebuilt master cylinder.
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