As far as the "tar like substance, " I'm not sure. Brakes will sometimes get a build up on them if there is a bad wheel seal that allows grease to get on them or the wheel cylender is leaking. The grinding noise you heard was most likely just rust.
As far as the wheel cylender, if you pop off the rubber boots on each side, they should be dry. If they are leaking, they will be wet with brake fluid. Also, most times if they are leaking, you will see a build up of dust and brake fluid on and around the rubber boot. If leaking, they need replaced or rebuilt. Honestly, it's easier to replace them because they are cheap. You need special tools to rebuild them and it isn't worth the time.
Let me know if you have other questions.
Thursday, July 16th, 2009 AT 12:04 PM