Sinking Brake Pedal

While sitting at a light I am able to press my brake pedal almost all the way to the floor. It sank rather slowly, but never lost brake effectiveness. Is this a "feature" of low idle speed and subsequently low air pressure for the brake booster or do I have a malfunction? Fluid level good, braking normal, first application firm, but keeping pressure on pedal results in sinking pedal. Situation is consistently repeatable.

'02 Jetta Wagon
45K mi. 5 speed
1st problem!

mabee your master cylinder is starting to go out.


my '02 does not do this.

It sounds like you may have fluid leaking internally in your master cylinder.

see-ya matt

Yeah, classic symptom of a bad master cylinder. The car seems to young for that, though...

I found that this happened after I changed my brake pads -- even after the piston took up the slack.

The problem went away as soon as I changed the brake fluid. When was the last time you had yours changed?

After a brake job I like to check the play in the brake pedal. Mine sunk to the floor also, but only if I pushed down hard on it- with continuous pressure. I asked about this and was told it is normal- if you have ABS.

I also thought it was the master brake cylinder, since this was a classic symptom in my old jetta, but supposedly not with the newer Jettas and ABS. I have no problems braking and the ABS system works fine. If you do not have ABS then it is the master cylinder or a leak somewhere in the system. The latter will result in fluid on the floor an a lower level of brake fluid.

Since then, some many months ago, I have seen not reduction in the brakes performance. If it was a master cylinder problem, I would also see a sinking pedal when braking normally, but I do not.


On my first Golf, they had a class problem of failure of the brake line under the drivers side carpet. Bad stuff. Happened to me. It was caused by water leaks on the driver's side. Also did a job on the fuse box.