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Discussion Starter #1
2001 4.6L vogue.
I've searched for abs type issues, but only found "clicking" pedal and lots of pedal movement, so:-

Started as "abs type" intervention when turning / parking, with made me think it was a sensor / reluctor, but has developed into banging through the pedal.
Now happens when travelling straight as well.
I sometimes get a heavy banging through the pedal( both feel and audible). This is not the gentle pulsing of ABS.
Occasionally the pedal is hard with little braking, until I push through this.
Often there is a loud "boing" spring noise !
I get a variety of ABS and Traction Control lamps lit, but not in any particular pattern. The startup selftest bit is normal. Sometimes they go out after a short time, sometimes they stay on.

The brakes are physically in good condition with good discs and pads, and free guide pins and calipers.
They don't feel spongy at all.
Vehicle stops in a straight line with the correct braking power on the occasions it doesn't "bang" or "boing".

Oh, and no faults on an OBD tester. Maybe they would only show up on a dealer diagnostic?

I haven't replaced anything yet.

Thoughts?
 

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It's not, that issue only applies to GEMS, the OP has 2001 Bosch.
 

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I've also experienced that "springy boing" noise and sensation on the brake pedal before, typically in the morning when I'm reversing out the garage and the ABS pump is still doing its thing and i brake to stop. I won't be applying a lot of pressure and I'll hardly be moving when it happens. Also a 2001 Bosch by the way. Rave says "When the ABS system operates, the driver will experience an audible noise from the ABS modulator and vibration transmitted through the brake pedal." so I've always just assumed it was that, not sure why it would go off under the circumstances I've described because I really doubt there were any wheels skidding at the time.
 

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I believe what you are reading about ABS in Rave is that under "Normal ABS" operation, the modulator will do just that....Modulate the brakes. This is felt as a click, or series of fast clicks in the brake pedal as well as very audible clicks from the hydraulics. Try a hard stop on a gravel road, or while turning and going over a bump, and you will hear and feel the ABS system kick in.
The Boing in the morning, which I have heard from both of my 02s is, I believe, the sound that a spring loaded, fast acting shuttle valve in the modulator would make if the system detects braking, and inadequate fluid pressure in the powered side of the system. It will shuttle to bypass ABS and open up ports on the manual, non powered side of the system to continue to provide stopping power, although weak compared to powered operation.
The reason for first thing is that there is simply not enough pressure built up in the system yet by the pump. If I wait about 30 seconds to give the system time to pump up, I never hear the Boing.
I read the entire post mentioned above and now I am very curious about the modulator and it's internal workings. I may need to get one from the wrecking yard, and take it apart to see just what makes it tick....Or Boing!
 
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