1999 GMC Sierra brake problem
When you change the master cylinder it is best to gravity bleed first, then proceed to the pedal technique.
Gravity bleeding is when you just open the valve and let gravity pull the fluid down.
Keep in mind you must "prime" the master cylinder first before installing it, did you do that?
Priming the master cylinder is where you put it in a vise gently, you then take apaptors and screw into the outlets, then take tubes from the adaptors back into the resoirvor. You fill the resorvoir up with fluid and take a 3/8 extension for a socket and push the piston in and out slowly until there are no more air bubbles.
After this procedure you gravity bleed the brakes, then go on to the pedal technique.
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