I had this in the technical forum but it's not getting many views and no responses. So put it here for more visibility. Thanks

On the way home from work today and pulled into Walmart parking lot, when I applied the I heard what sounded like a slapping noise. When I let off the brake it stopped. Parked went in a got what I needed.

I had a short ride to my apartment from there and when I left the ABS light was on, but brakes still worked.

I shut off the when I stopped to pick up my mail. When I got back on the ABS light was off but still hearing the slapping noise when I apply the rear firmly. I also feel a slight pulsing through the rear brake pedal even when applied slightly.

The ABS still seemed to work when I applied the brake quickly and hard. The also seemed to occasionally be slightly firmer then normal but not all the time.


Pads were replaced about 6 months ago and brakes bled at the same time, flushed the brake system about a year ago.

I haven't had time to look at it yet, but any ideas?

FOLLOW UP:

Pulled the rear caliper off and made sure all 4 cylinders were working, they are. I bled all 3 brake cylinders and didn't appear to be much air, if any. The ABS function still seems to function when I slam on the brakes (both rear and front).

However, the master cylinder was low brake fluid..but I don't think enough to cause air into the system, but can't be sure. Let's say some air got into the ABS module, would that cause the pulsating I'm feeling when I press the rear brake pedal? It happens even when I just softly apply the brake.

When I pull the ABS fuse, brakes work as normal without ABS.

The front brake doesn't do it, only the rear. Are the front and rear ABS system totally separate?

 

Chances are the circular float on your rotor has seized. When this happens the rotor can be stuck on an "out of round" rotation. I would suggest placing a towel or taping off the rotor below the float and hitting it with pb blaster. This float should be able to be moved with your fingers (vertical movement).

I know this because while coasting down an empty (under construction) 7 story parking garage. I heard a repetitive squeak or slap and when I applied the brake there wasn't a large pulse cause I was going slow but there was a pulse.

My float had seized, once I got it free'd, no squeak and no pulse...

and a valuable lesson when I do my checks... I need to verify they are free. I recently added checking the torque on the exhaust nuts too. mine backed out a little during a trip to yosemite.

 

FOLLOW UP: (I updated the original post)

Pulled the rear caliper off and made sure all 4 cylinders were working, they are. I bled all 3 brake cylinders and didn't appear to be much air, if any. The ABS function still seems to function when I slam on the brakes (both rear and front).

However, the master cylinder was low brake fluid..but I don't think enough to cause air into the system, but can't be sure. Let's say some air got into the ABS module, would that cause the pulsating I'm feeling when I press the rear brake pedal? It happens even when I just softly apply the brake.

When I pull the ABS fuse, brakes work as normal without ABS.

The front brake doesn't do it, only the rear. Are the front and rear ABS system totally separate?

 

" When I pull the ABS fuse, brakes work as normal without ABS. "
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Does that mean the slight pulse in the rear pedal is gone when the fuse is pulled?

 

This problem has been around since the frame change in 2009. It has nothing to do with the rotors or ABS. If you do some looking you will find the reason for this. Seems if you use front and rear brakes together there is no problem.

 

Yes, it is gone and brake works.

 

This literally just starting happening three days ago so I have a hard time believing it's normal. Something is causing it, will probably take it in to the dealer tomorrow.

 

Did you replace the rear tire lately? The reason I ask is that sometimes, if you're not careful, you can tweak the rotor and cause the rotor to warp. I did it once and had to dial indicate and straighten mine to get it back to normal. It worked and I didn't have to buy new. I'm cheap and if I can fix the problem, I will.

 

Ended up being the rear wheel bearing and the sensor in the bearing causing the ABS problems.