Reader Question: Austin,
My 1996 Renault Clio shake/vibrate when I step on the brakes at 40mph. At low speeds of 10-20mph, it does not seem shake/vibrate as bad.
I changed the brake pads and rotors six months ago. I drove it for six more months and it kept doing it. I then changed the driver’s side caliper because the vibration/shake seemed to be coming from there, which is on the right hand side of the car in this country.
When I was bleeding the brakes on the new caliper, I had to pump it several times to bleed it. The fluid in the master cylinder looked really dark not clear but I left it as is. After that I took it out for a test drive and it stills shakes/vibrates when I step on the brakes.
Do you think the master cylinder is bad? Do you think the fluid is bad and needs changing? Do you think I may have warped the new rotor prior to replacing the caliper?
What are your thoughts?
If you can feel this shaking/vibration in the steering wheel then it is most likely coming from the FRONT brakes, and probably a warped brake rotor is the culprit.
If the steering wheel really does not shake as much as the brake pedal or the rest of the vehicle does when this vibration is felt, then there is a possibility the problem could be coming from the REAR brakes.
I would find a large empty parking lot and slowly stop the vehicle with the emergency hand brake, which only uses the rear brakes. If you feel the vibration when just using the hand brake, you have warped rear rotors or drums.
If the vehicle brakes smoothly with the hand brake, then I would have the front brake rotors machined and see what happens.
I have installed “new” brake rotors that were warped right out of the box. Also, if the brake rotor or wheel is not installed correctly in a star pattern it can put the rotor in a bind and cause it to be crooked and off center, which can also cause a brake vibration.
If the brake fluid in the master cylinder is black, yes I would flush it out or just open the brake lines at each wheel and let gravity suck out the black fluid as you add new clean fluid to the reservoir. This process can take an hour or so, but is the safest way to bleed brakes. I do not feel the dirty fluid or the master cylinder is the cause of your vibration though.
Here is more about brake rotor warp: