no brakes help

[bigjoe21]

I have a 1996 chevy tahoe with a 5.7 litre engine ABS A/C P/S 4 wheel drive my problem is sometimes when I step on the brakes the pedal goes to the floor. I have had 4 new master cylinders installed in 2 different states in different shops Ive replaced the steel brake lines rotors drums wheel cylinders calipers pads & shoes and still have the pedal go to the floor. This every couple of months. any help any can give would be great. Afraid to use the car.
thanks.

 

[ezdaar]

wow. all that from two different shops and they completely missed the problem.

Your master cylinder is shot.
Go ***** at the closest shop and have them fix it this time.

 

[chaingun427]

He said they've replaced the master 4 times. I had a similar problem when I let my system drain due to broken line, ended up screwing up my abs motor.