cshaida

I've been having a constellation of possibly related issues with the PDAS/Anti-lock/Brake Pressure warnings. I've read pretty carefully (I think) a lot of the prior threads and they've helped quite a bit to untangle what might be separate issues. Th particular issue I'd love some guidance on has to do with the recent change in the actual action of the brake pedal.

Right now on virtually every stop the pedal 'pulses' (or experiences 'stiction' in John Boggiano's phrase) ONCE just before the car comes to a complete stop (at maybe 0-3 mph). The pedal stays firm, brake pressure is live (ie, it doesn't feel like there is a loss of braking), it's just that the brake pedal 'resets' or 'hiccups' and a minor addition of foot pressure fully re-engages the pedal. We've tried different kinds of extreme or aggressive braking (in very safe places, of course!) and experience no hiccup or stiction or pulse at higher speeds--just at the very end, at very low speed.

Visually checked brake fluid level (seems fine), have looked at the components of the system in the boot and don't see any leaking), have not looked at the individual brake calipers.

Any ideas for further diagnosis?

THanks

darth

If I undersand you correctly you're experiencing a false ABS condition. The ABS activates when it senses a mismatch in one or more of the 4 wheel speeds. I'd look at inspecting / cleaning up the wheel speed sensors checking the electrical connector conections first as they're the easiest thing to check. If you have access to a multimeter you can measure the AC voltage output of each sensor and by comparison of the 4, determine which one(s) are suspect in order to narrow down the investigation.

Bill

Indycam

I would start by unplugging the abs computer .
Does the symptom go away ?

Indycam

Have you cleaned your accelerometers ?

cshaida

darth: a 'false' abs activation kind of makes sense (since it's so consistent). I do have a multimeter and can check that (I don't know exactly which wires are which but I'm sure I'll find pictures here or elsewhere).

indycam: will try unplugging the abs computer; have not cleaned (but have read about cleaning!) the acclerometers. I'll read up more carefully and see if it's within my (very small) sphere of competence.

Thanks for the tips!

darth

There are 2 wires coming off the sensor, so just connect the multimeter leads one to each with a paperclip at the connector and try and put on the lowest scale to get maximum deflection. Don't worry about polarity but try to be consitant on all sensors. You can get one or all the wheels off the ground and just spin it noteing the voltage.

Bill

DAVISRILEY

How bad is your brake squeel? When mine is bad, I will get a pulse at every stop. No squeel, no pulse. Also, when mine pulses, does your speedometer bounce up? Good luck.

cshaida

no 'squeal' really but there is a little 'burp' and no speedometer bounce that I've noticed but I'll watch carefully next time out

DAVISRILEY

My abs only kicks on when the brakes squeel loudly. Trust me, you wouldn't miss it. Small children, dogs and the elderly duck for cover when my car stops most of the time. It's what I get for running no spiders. O well.