I know this is a commonly asked question (yes I have read previous posts) but there seems to be no definitive answer. I am positive that I did not introduce air into the brake system.
Following a 2-yr pressure bleed brake fluid change, I noticed that, while the engine is running, I can keep a steady medium-high pressure on the brake pedal and it will slowly go almost to the floor.
With the engine off the brake pedal is firm and high - no sponginess whatsoever - one depression meets with immediate, firm and unyielding pedal feel - would seem to indicate no air in system, good master cylinder etc.
The brakes including the ABS work very well - just this strange spongy feel when you sustain pressure on the pedal while running. EG - firm pedal with engine off - start the car with foot on brake - after engine running, pedal will slowly depress almost to the floor. Some depression after startup indicates your booster is working, but this is a bit much.
All pads are good condition and hand brake is used and works well.
I re-bled the brakes via the manual method - no change. I am positive that I did not introduce any air via either bleed.
I can't be sure that the pedal has not always been like this - I just noticed this following a fluid change.
I read one post about using a VAG-COM to cycle/bleed the ABS pump: anyone have success eliminating this problem by this method??
This type of pedal feel seems common to TDI's with comments that it's normal and acceptable - can someone explain why this would happen and why some vehicles don't do this?
Thanks for any help.
2002 Jetta TDI
Following a 2-yr pressure bleed brake fluid change, I noticed that, while the engine is running, I can keep a steady medium-high pressure on the brake pedal and it will slowly go almost to the floor.
With the engine off the brake pedal is firm and high - no sponginess whatsoever - one depression meets with immediate, firm and unyielding pedal feel - would seem to indicate no air in system, good master cylinder etc.
The brakes including the ABS work very well - just this strange spongy feel when you sustain pressure on the pedal while running. EG - firm pedal with engine off - start the car with foot on brake - after engine running, pedal will slowly depress almost to the floor. Some depression after startup indicates your booster is working, but this is a bit much.
All pads are good condition and hand brake is used and works well.
I re-bled the brakes via the manual method - no change. I am positive that I did not introduce any air via either bleed.
I can't be sure that the pedal has not always been like this - I just noticed this following a fluid change.
I read one post about using a VAG-COM to cycle/bleed the ABS pump: anyone have success eliminating this problem by this method??
This type of pedal feel seems common to TDI's with comments that it's normal and acceptable - can someone explain why this would happen and why some vehicles don't do this?
Thanks for any help.
2002 Jetta TDI
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