Braking changes after 5MPH

[DieselDavey]

Hello again,

Since I've had the Burb, the braking behavior has always changed when slowing down below 5 MPH.

Lets say I'm traveling at 40MPH, slowing down for a stop light. When speed decreases to 5 MPH, the bake pedal suddenly drops then feels notchy (hope that makes sense). Pushing down on the pedal (from 5 and below) seems to move in steps.

The vehicle always stops just fine. It just seems to be a strange behavior.

I assumed that the change was due to the RPMs on the power steering pump slowing. I installed a new pump (due to catistrophic failure, the shaft broke), and the brakes behave the same way.

Anyone else experience this? Do you think it indicates a failing booster?

Thanks.

[JTodd]

Something is wrong with your ABS. A working ABSystem deactivates below 5mph - it would appear that yours is not.

[Robyn]

Try this.

Get ready to do a stop from say 40MPH shift to Neutral and keep the rpms up to, say 1200 or so and then do the braking. See if having a little more rpm (Oil pressure from the pump) helps the issue.

If this does not help then ABS is probably having issues.

An issue with the ABS should show a code or at least the light should come on to alert you to an issue.

If the extra RPM's stop the problem then I would suspect the booster has issues.

Lower oil pressure with a booster that starting to fail can result in some hinky things happening when braking.

Let us know

Robyn

[diesel65]

Common problem for which GM has a service bulletin, The ABS is kicking in around 5 mph because it lost a wheel speed signal.
The fix is first connect a AC millivolt meter to the ABS wire connector from the bearing hub then spin the wheel by hand,(check left side and right side) you should get a reading of approx 350 millivolts. If not, then pull the rotor and hub assembly and then remove the speed sensor from the hub assembly. Where the sensor was mounted scrape and clean any rust and scale that is present. When done apply a film of grease over the surface and reinstall the sensor. Reassemble the rotor to the vehicle.

The rusty scale builds up under the sensor and heaves it causing a weak signal at low rpm.

[DieselDavey]

Thanks 65 and Robyn,

I have felt the dirty sensor symptom... Only once in a while. So for sure I have a dirty ABS Sensor.

The "Notchy" or different "steps" in the pedal as it goes towards the floor is a completely different feel than the very quick ABS modulations.

I will of course clean the sensor. Also a great idea to use neutral to keep the revs up whild stopping.

Thanks,

I'll work on it this weekend and let ya know what happens!