Pulsating brakes..

Hi,

My mom's malibu recently broke down and I let it sit for about 3 weeks before I fixed it. After I changed the lower intake gasket, I got it running and took it for a test drive. Ever since, the brakes have been pulsating and the car vibrates when I break. My friend's car had a similar thing happen to his breaks after his car sat around for a few weeks, but his brakes went back to normal. My mom's car still has pulsating breaks after 1 week of driving.

Your rotors have warped, you need new brakes. If it shakes in the steering wheel, you need fronts, possibly rears as well. If it doesnt shake in the wheel, then you need rears.

I figured as much. I just don't understand how that happens when the car is sitting still...

The brakes didn't warp, they rusted. Rotors are cast iron. It doesn't take long for them to rust like crazy. The part covered by the pads tends to stay pretty clean, but the rest of the rotor is rust central.

And you may not need new brakes. Since you've driven it for a week and it still has a pulsation, the rotors are probably warped. If the rotors are thick enough, they can be machined/turned so that it runs true again. Be sure when reinstalling them that there is no debris on the hub or rotor mating surface and that you properly torque the wheels when reinstalling them. If you hammer the lugnuts on with an impact wrench, you may warp the rotors again.

-Rod

An impact gun will only warp rotors if you are an idiot. Torque your wheel nuts down gradually and in the correct star pattern, and you will never warp a rotor by bolting a wheel on. Assuming there is no debris between the rotor and hub.

A lot of the time, new rotors are around the same price as having a shop turn a pair for you.

Unless they are machined very acuratley you may well still get some vibration or pulsing, I wouldoptfor new discs, front first as they take more of a pounding.

We received rotors from the store that were warped and needed to be machined. I've never had a rotor pulsate after being properly machined. I'm not sure if that's due to the way they stock them on the shelves (on end rather than flat).

O'Reilly Auto Parts around here will machine rotors for $11 each.

-Rod

The critical thing is PROPERLY MACHINED