I have a 2010 2500 GMC sierra 4 door work truck it has over 200k miles.. when im driving and i stop it stops fine but as im waiting on the red light the car starts to slowly move forward so i have to step harder on the pedal to the point that the pedal goes all the way down.. i check my brakes & they seem to be good and i dont see any leaks on the back of the tires.
my brake fluid reservoir was very low so i filled it and I thought that will solve the problem but the problem still there...
Any thoughts i appreciate your time
Thank you
Your master cylinder is probably leaking into the brake booster. If this is what's happening you not only need a new master cylinder but it will ultimately ruin the booster.
Thanks for your help..
Quick question
So I should replace the brake booster and master cilinder at the same time?.. or change the master cilinder first and then see how it goes?
If the master cylinder leaked internally to the booster, you may change the booster as well.
Yes, @vic, to be on the safe side in that situation change the brake booster as well.