Pdas & abs & warning horn intermittent problem

[Maych87]

I am having an issue with my 964 pdas and abs warning system. There is so much information on this issue that I do not know where to start. Here is the info I have gathered and I am wondering if someone has any ideas on how I can correctly diagnose the issue without the Bosch hammer.

1. If the car sits overnight and I turn the car on the abs & pdas lights come on as well as the warning horn that beeps 16 or 17 times. The light does not turn off for the entire drive.

2. If the car sits overnight and I turn the key to run to allow the pump to turn on it runs for 75 seconds before it turns off. If I then start the car there are no lights. Sometimes the lights remain off. On longer drives they sometimes turn on.

3. I have replaced the accumulator and bled the entire system several times with a power blender and get no air.

4. The fluid level is right at the max level and I have no battery issues.

Please help


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[Maych87]

Tests I did today.

5. Car sat overnight. Pedal was hard as if there was no pressure left in the accumulator.

6. Turned key to on let the pump run until it stopped. Timed it with a proper stop watch this time and it took 54 seconds to turn off and pressurize system.

7. Once system at operating pressure with the key still in the on position I pumped the brakes. If I pump it 4 times the pump turns on for 10 seconds.

8. If I let the system get to operating pressure, then wait 1 minute and pump the brakes. It only takes 2 pumps to activate the pump.

It seems like I have a problem holding pressure. Is there a way to confirm this. Is it possible that I got a faulty accumulator or that I still have air in the lines. Or am I way off and is there other possibilities. The fluid level always remains the same so I can't imagine there being a leak.

Suggestions please




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[Maych87]

9. Let system fully pressurize. Pump pedal, 31 pumps until brake pedal goes hard.

10. Let system pressurize. Leave vehicle for one hour. After an hour pump brakes. Took 28 pumps and pedal went hard.


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[Paperboy]

If your brakes and ABS are working seemingly ok but you are still getting warning lights, two Quick tests. Clean the connector to the PDAS/ABS computor . Also try overfilling the brake fluid ever so slightly. No expert, but minus light and buzzer your system doesn't behave that much different from mine.