I replaced my pads on my 2004 chevy silverado and bled the brakes. I know I did all this right. The brakes are fine until I turn the car on. Then the brakes go right to the floor like the system is full of air. I have 130K+ on this truck and hear that they were made with faulty master cylinders. I can change that very easily. My question is how do I know it is not the brake power booster unit. Is there a way to check the master cyl vs the power unit. Thanks for your help,
If you're not leaking anywhere-and is sinking to the floor-replace the master cylinder, its not coming from the booster
August, 21, 2011 AT 4:48 PM
I have thoroughly checked for leaks (thinking that was the problem).
I will replace the master cyl and start from there.
August, 21, 2011 AT 5:25 PM
I do have a question about bleeding the brakes on this truck. Should I try bleeding the brakes with the power on or with the truck running?
August, 21, 2011 AT 5:31 PM
You can do both as you wish and see what happens
August, 21, 2011 AT 5:35 PM
In your expert opinion, is it worth a try or just a waste of time?
August, 21, 2011 AT 5:43 PM
August, 22, 2011 AT 3:46 AM
I ordered a new master cylinder from Autozone (they were the only ones that could get it for me the same day). I received it at 5: 30 pm Sunday night. After I bench bled the new master cylinder per the new manufacturer instructions, I installed the MC. I bled the brakes, and I have done many disc and drum brake jobs over the years for my family and I (and we are all still alive), and the same problem still exists. The brakes get hard when we are sitting there bleeding them, but once I start the engine, they go straight down to the floor I have checked thoroughly for leaks and have not found any. Since I have replaced the master cylinder (MC), it seems like the only choice left is the power booster. Yet, a problem like this sure seems like there is air somewhere in the lines. It seems like there is a possibility that there is some sort of leak that I am not able to detect. I am thinking that my next move is to take it to a brake shop and get the system vacuum bled. What are your thoughts with my problem?
August, 22, 2011 AT 6:04 AM
Check if it has a hydroboost integrated the brake system
August, 22, 2011 AT 3:36 PM
Monday 8am. I have checked, and there is no reference anywhere to a hydroboost.
I have also checked again for leaks and it looks good. If this is all happening when I start the car, it seems like the power unit is the only thing left to check. What is your opinion?
August, 22, 2011 AT 5:26 PM
Okay-while engine is off -pump brakes a few times hold it in and start the vehicle the brake pedal should sink a little-did this happened if so -the booster is doing its job.