2005 VW Jetta: The brake indicator light came on in the dashboard. I took the car to the dealer, and they replaced the front brake pads. Indicator light is now off, but I drove away with a new problem: The pedal fades as it comes to a stop. I have to push almost to the floor to stay still. Sometimes the car drifts forward if I’m not consciously pushing down harder than usual on the pedal. The dealer took the car back for a few days, replaced the master cylinder, bled the lines and did not charge me. But the problem is still there. What went wrong?
The first guess would be that the lackey teenager they gave it to didn’t know how to bleed to brakes. The second would be that the new master cylinder was bad off the shelf. Have them tow it back there & give them one more shot at it.
Good thought. I had no problem with this until they replaced the pads, so the original master cylinder they replaced was probably not the problem. I’ll ask them to bleed the brakes again.
Actually, the process of changing pads & bleeding brakes stresses out the master cylinder. So it wouldn’t be too odd to have problems with after the brakes are done. It isn’t the most common thing but it happens.
Its also not too odd to get “new” parts installed these days and have them be no good. This can be for any reason that new things are defective, but it also could be that a rebuilt master cylinder was installed. This is not an uncommon thing to do for all sorts of auto parts and these days many rebuilt parts are bad off the shelf.
So its certainly possible that both your original & replacement MC are bad. Though its also possible that someone’s asleep at the switch on the bleeding. It is a simple and basic operation, but that doesn’t mean it can’t get screwed up .
I’m glad it’s just the brakes and nothing important to the safe operation of the car.
Thank you very much for this good info. I’m calling them in the morning.
I’m glad it’s just the brakes and nothing important to the safe operation of the car.
Usually one adds a little wink or grin of some kind for such sarcasm. It helps people sleep better at night 
For future work, especially very routine things like brakes, there is no need to take this car to a dealer. There might be the occasional something that a dealer may be better for. But in general just ask around among people that you know for a trustworthy, locally owned, independent mechanic. Some will specialize in VWs. You’ll typically end up spending less and getting service that is just as good if not better. (In this instance, lets hope better).
LAWeiss: I do hope you were joking about it being just the brakes and nothing important to the safe operation of the car. I have had customers decline replacing bald tires with the cords showing, shot brakes, loose ball joints and tie rod ends, and repairing significant coolant leaks in favor of repairing their air conditioning. They would usually approve this work and add something intelligent like, “We gotta have that a/c fixed. The wife and kids are taking this car to Chicago this weekend”. I would say the guy deserves a Darwin award, but he wouldn’t be in the car, “just” his wife and kids. Not sure what kind of award that would be…
Mark, you appear to be a good mechanic and a specialist in abnormal psychology. Some people out there need both. Of course I’m joking about the brakes being unimportant to the safe operation of the car. With all kidding aside, it seems to me that the dealer should not let the car roll out of their shop with an uncertain conclusion about the result, even if they don’t charge for the return for correct service. What if my family were in an accident because they did not bleed the brakes correctly, or installed a faulty ‘new’ master cylinder. This is the stuff that keeps ambulance drivers and attorneys busy.
You have to bench bleed the master cylinder before you install it. Then you have to bleed the brakes. This is usually done with a machine now. Shops do not take the time to pump the brakes and it takes 2 people. If bleeding was not done correctly than you would have this problem. Air compresses much more than brake fluid, which is why your pedal keeps going down as you push on it.
This could be a problem with the brake booster.
Does the pedal feel stiff or soft when this happens?
I suspect that Knfenimore hit the nail on the head.