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Hydraulic Brake Operation

With car stopped if I apply continuous pressure to the brake pedal the pedal will slowly sink. I thought this meant air in the lines or a fluid leak. If I pump the pedal it rises to a higher point than I started at. Otherwise, the brakes work fine.

Dealer says they all do that, not to worry.

What’s up with that?

Dealers always say “they all do that”. Sorry dealer…they don’t. If your pedal keeps sinking then there is air in the lines or the brake fluid is leaving the vehicle. A good mechanic can check this out for you. It may be the master cylinder, wheel cylinder, cracked steel line, cracked rubber brake line or fitting if air is not in the system. In any event, your brake system needs attention right now.

As the car ages, it’s likely a worn master cylinder with fluid simply being sqeezed past the piston. Not that difficult to fix, but might be expensive on a Volkswagen.

As Docnick said above, your symptom is most often indicative of a worn master cylinder. One way or another, I would for sure change the dealer. From what he/she tells you, they are highly incompetent. Besides, unless your car is still under warranty, there is NO reason to go to a dealer. A good independent mechanic is all that you need. If you can find one who specializes in VW’s, then it’s even better.

OK Here’s the rest of the story.
I did go to another mechanic who removed the wheels, disassembled the brakes, removed the pins the pads slide on to check for smooth operation and bleed the lines. He thought if the calipers weren’t centered air could enter there. After determining there were no problems at the wheels he told me the problem was most likely in the master cylinder and as the car (2006 Jetta with 43,000mi) was still under warranty the dealer should fix or replace the master cylinder.
The dealers mechanic demonstrated to me with two of the cars waiting for service that this was a common condition and not problem.
It just seems wrong.

It is wrong. Those vehicles will have to be repaired. Brake pedals do not sink to the floor if the brake systems work properly. No way…no how. I am confirming your suspicions as others have previously.

One question here:
Does this sinking pedal happen all the time, or only when you have the A/C system (either on heat or cool) running ???

He thought if the calipers weren’t centered air could enter there…

Here is another tech (independent?) that ought to know better. The m/c being bad is correct but there is no logic in the caliper being centered comment.

I haven’t had the A/C on yet as I only bought the car 1/8/10. I don’t know about the centering thing, but this all started because the rear brake was making a scraping sound. One wheel had a problem (driver side rear) that gouged the rotor and ground the pads to no brake material being left. So I had that fixed by a mechanic that didn’t have time to properly bleed the brakes. Told me to come back next week and then left town and left me a phone message saying he wouldn’t be back for a few weeks. A second mechanic was the one who told me about the centering thing and determined that (centering) was not the problem or anything else at the wheels.
The Toyota problems have me wondering if there is something different about brakes now.
The Jetta has a stability control feature which applies the brakes selectively to correct for traction loss on one of the wheels. Of course it’s a front wheel drive so why it would mess with the rear brakes?? Obviously I don’t understand that system.
I do believe hydraulic systems should be closed and any entrance of air or water is to be prevented. So I have sent a email to VW customer service and am going to be very interested to see if they think all VW’s are like this.

This is an absolutely normal condition designed by the manufacturer to create a certain “feel” to the breaking system. If you have the car off, and pump the breaks, then hold them it should not sink. If the other cars at the dealership have the same feel, it is not an issue. You also can not compare different year or make cars as they are all designed differently.