AJK

Sun and in the 40's in upstate NY, so I took the car for a run. At the start, the brakes were smooth and stopped the car well. As the ride progressed, I got a pulsing in the pedal which seemed to get more pronounced the more the brakes were used. I thought once a rotor was warped it stayed that way, whether hot or cold. This same phenomenon repeated itself after I stopped and resumed the drive.

And ideas on the cause?

Garth S

Yes, rotors do not 'unwarp': to check for warpage, demount the wheels and spin each rotor against some immovable reference point. This is the quickest way to check for lateral run out .. aka 'potato chip' rotors. Any point on the caliper will serve as reference; however, on the front, assure that the wheel bearings are tight prior to testing.
The early calipers are somewhat prone to sticking on the machined sliding faces, especially after periods of storage. That could be a cause, as could a sticking piston. If either has been advancing over some time, you will see asymmetric wear on the brake pads. Also, check the wear pattern on the rotors.

perrys4

I had a sticking piston and the wheel got so hot you couldn't touch it for 20 minutes. Rotors are easy to replace and not very expensive.

IcemanG17

Did you feel anything through the steering wheel?

mark kibort

i had a MAJOR saga with my BMW. turned out 5 years later of chasing huge vibrations in the steering wheel (and you could see the front wheels moving back and forth) turned out to be dragging brakes due to the bad master cylinder. the brakes were fine, if the master wasnt dragging, but once they did, it was pretty bad.

Usually, a stuck piston will make the rotors hot and warped all the time.

MK

perrys4

Sorry for the big delay. Actually I didn't feel anything though I was freeway driving. It happened on my way to Precision for an oil change. Greg and Ken said I was lucky the thing didn't catch fire. Made me a little nervous.

AJK

Thanks for your replies.

Iceman: Yes, I freel it in the steering wheel, big time.