Spongy Brakes
#11
05-06-2012, 12:01 PM
I had the same problem until I bled mine the opposite direction. On these cars I've read that you should start with the wheel nearest the master cylinder and then move to the one furthest. FL-FR-RL-RR.
I bled mine using a homemade pressure bleeder that made it really easy. I have heard that using the two person pedal technique can damage the seals in the master cylinder because the piston is compressed further than typical.
I bled mine using a homemade pressure bleeder that made it really easy. I have heard that using the two person pedal technique can damage the seals in the master cylinder because the piston is compressed further than typical.
Bleeding Sequence
1. Right-rear brake caliper.
2. Left-rear brake caliper.
3. Right-front brake caliper.
4. Left-front brake caliper.
#12
05-06-2012, 02:11 PM
I'm thinking my problem may be the brake booster or something affiliated to it (vacuum pump, etc).
Reading through the troubleshooting section of the Bentley A4, B5, regarding the Brake Servo (AKA brake booster) it says:
- With engine switched off, depress brake pedal firmly several times (to deplete vacuum in brake servo).
- Depress and hold brake pedal with average foot pressure and start engine. If servo is working properly, pedal will be felt to give slightly underfoot (servo assistance becomes effective)
My car seems to pass this "giving underfoot" test, but I wonder if the booster is still the problem. I'd hate to cough up another $300 just for parts and find it's not the problem.
At this point, I doubt I have a problem with air in the brake lines, but it's still spongy.
I can pump the brake pedal and get it solid, but it gets soft after a few seconds of engine running. What thinks the board?
Reading through the troubleshooting section of the Bentley A4, B5, regarding the Brake Servo (AKA brake booster) it says:
- With engine switched off, depress brake pedal firmly several times (to deplete vacuum in brake servo).
- Depress and hold brake pedal with average foot pressure and start engine. If servo is working properly, pedal will be felt to give slightly underfoot (servo assistance becomes effective)
My car seems to pass this "giving underfoot" test, but I wonder if the booster is still the problem. I'd hate to cough up another $300 just for parts and find it's not the problem.
At this point, I doubt I have a problem with air in the brake lines, but it's still spongy.
I can pump the brake pedal and get it solid, but it gets soft after a few seconds of engine running. What thinks the board?
#13
05-06-2012, 04:06 PM
I had the exact same symptoms. I would still try bleeding with the reversed direction. I had an okay feeling pedal but wanted to flush the dark fluid out. I never let the reservoir get low, but when I was "finished" I had a soft pedal that would get worse when the engine was running. At this point I had flushed almost a liter through and the fluid was clear.
I went the other direction and actually got some bubbles at both front wheels. I ran another half liter though and the pedal has been rock solid ever since.
I went the other direction and actually got some bubbles at both front wheels. I ran another half liter though and the pedal has been rock solid ever since.
#14
05-09-2012, 04:47 AM
I had the exact same symptoms. I would still try bleeding with the reversed direction. I had an okay feeling pedal but wanted to flush the dark fluid out. I never let the reservoir get low, but when I was "finished" I had a soft pedal that would get worse when the engine was running. At this point I had flushed almost a liter through and the fluid was clear.
I went the other direction and actually got some bubbles at both front wheels. I ran another half liter though and the pedal has been rock solid ever since.
I went the other direction and actually got some bubbles at both front wheels. I ran another half liter though and the pedal has been rock solid ever since.
My ABS light is on.
I also went through a bunch of brake fluid -- it's ALL really clear now.
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