Break problem

[Jurmy22]

I have a 2003 Chevrolet Silverado 1500 with the 4.8 liter in it. In the last 2-3 years I have replaced the master cylinder break lines and calipers, recently the break pedal started going to the floor when trying to stop, it does stop but takes longer, this truck has a vacuum pump on the break booster, I disconnected the vacuum line and the breaks feel closer to normal and don’t go to the floor. When the truck is off I can pump up the breaks but as soon as I start it and press the pedal the pedal will go to the floor it does come back up though. Any thoughts on if this is a bad break booster or something else I should be looking for? Any help is appreciated.

[Earl Cordova]

Brake.

[Grumpy Bear]

Master cylinder  

[Grumpy Bear]

double post sorry. 

Edited August 6, 2021 by Grumpy Bear

[dna9656]

Your brakes are super important, I think you got a vacuum issue. If it were my truck I'd take it to a well respected shop that offers free inspections. Let the guys who do it to put food on the table and the roof over the heads of their kids tell you what it is; then if you feel like you can do it you can fix it with more confidence or hire those guys and pick it up at the end of the day, ready to perform with a warranty. Don't forget to patronize those guys when you need to. They need love too.