Brakes pulsating Here is what I have tried: Turning front rotors first then New Rotors. New Calipers, Turned rear drums twice,then New Rear drums, Pulled axles and checked. New wheel Bearings. New brake shoes in rear. I have no idea what is causing the problem. The vibration is so bad loses road stability going downhill at 60 mph. Only does when slightly braking. Gets worse as braking harder. I clamped off the two hoses to the rear brakes and the Vib. went away. Folks tell me this is not an indication that it is in the rear due changing brake config. HELP.

SOURCE: pulsation in brake pedal and rear end hops during braking

What happens is if you have a bad front wheel bearing when you brake that wheel will turn in or out,when this happens it throws the four wheel alignment out and since this is a solid rear axle,it's forcing it to flex on the suspension,wich could cause the rear tires to bite on the outside edge of one tire and the inside edge of the other,thats one possible the other would be that the rear brakes are are not slowing the wheels evenly causing the same issue.I saw this problem with a bad front wheel bearing on a Nissan Pathfinder but not as pronouced due to the independent rear suspension. Check the front wheel bearings,which of course will mean getting the calipers off the rotors,and then check for any movement in the rotor,if there is check the hub nut,if it's loose tighten it and check for play in the rotor if there is still play that's going to be caused by a bad bearing.You can check the braking in the rear with a simple spring scale(like the ones used for fishing),with the wheels removed have someone apply enough pedal pressure to just engage the brakes but still allow movement attach the scale hook to a wheel stud and pull until it starts to move and note how many pounds of pressure it takes to move the hub.If it's uneven chech your adjusters and even them if needed and then retest,if still uneven you'll need to bleed them again.As far as the dark black substance in the fluid I would say you may gotten a contaminent in the fluid.Brake fluid gets kind of a rusty reddish residue when it breaks down.If I missed anything or you need clarification don't hesitate to ask I'm home all day.Hope this helps solve your problem.

Ned C Cook

• 3433 Answers
• Posted on Jun 29, 2009

SOURCE: 1999 Chevy tahoe 2dr Brake shudder intermitant hard pedal.

Previously mentioned proble. Turned out it was the ABS. I'm sorry I can't remember the part name but I believe it was the main distribution module. But, it is the ABS.system for sure