QuestionJohn -
2003 Discovery HSE7, 48,000 miles
First off, thanks for the advice you provided about a month ago in regards to my AC problem. The cabin was not cooling off at any setting. The dealer ended up installing a new heater box. A damper door was stuck and not distributing cold air to the passenger side. It's fixed and cooling like I'd expect.
Now for the question: I decided to replace the rear brake pads and rotors on the Disco. It was fairly easy, two caliper bolts, two mounting bracket bolts and the philips set screw and the rotors came off. I bought Wagner pads, some type of high-end high metallic pad but forget the name (supposedly a direct replacment for the more expensive OE pads). I was pressed for time so ran to the dealer for the rotors at $90/ea...ouch. Sprayed the "blue" rotors with brake cleaner and installed the new rotors and pads. It's been about 3 weeks and now I have recognized a clicking (metal to metal) sound coming from the rear driver's side wheel. It is associated with the revolution of the wheel, faster at the start of brake application and slowing down as I come to a stop. The clicking occurs periodically, if I press lightly on the pedal, no noise. If I jump on it, limited to no noise. It's at its worst when the pressue is medium or normal pressure...and definitely stops as soon as I take my foot off the brake. I just removed the pads, caliper and pad holding bracket tonight and tried to secure all bolts, but still the clicking occurs. I'm at a loss and about to bring it in to the dealer. Is there something I missed? Bad pads? Over-tighten or under-tighten some bolts? I can't believe the rotor would be warped. It almost appears like the pads seize to the rotor and bangs against the holding bracket or the fluid pressure varies but why not on the other rear rotor? I'll stop writing and see what insight you might be able to provide.
Thanks.
Einar
AnswerHi Einar,
normally, the caliper adjusts the pad's distance from the rotor after you release the brake pedal. The rotors rotation should give a slight gap so that the pads are not constantly pushing.
Usually, if there is a noise coming from the brakes, it is due to the pads vibrating. There are special 'springs' that hold down the pads and should eliminate any noises. Sometimes these springs no longer provide enough pressure and a pad can vibrate. When you slipped your pads into the caliper on either side of the rotor, you had to also slip two cotter pins (or cotter-like pins) thru the caliper to lock in the pads.
On my '95 Disco, I also have two metal springs (or flexi-flanges) that press down on the pads and are held in place by the two cotter pins. If one of these springs is worn badly, it can allow the pad to vibrate.
Another problem could be the caliper. Perhaps a piston is seized or seizing and does not provide uniform pressure (either before or after) the brake pedal is pressed. Perhaps the piston rings are rusting or the rubber seal ring (beneath the cover ring) has turned and thus the piston does not retract properly. The only way to tell is to remove the pads and press out the pistons. Once the pistons are fully removed, you'll have to examine the rings that the pistons slide on. If you see rust or if the rubber ring is kinked, you'll have to replace them. In a pinch, you can clean the rust up as best as possible and try to reseat the turned rubber ring. I've done this..only it is a short-term fix that must be addressed soon.
The only other reason new pads and rotors would have noise is that the rotor has a warp. I've never seen one but I know its possible.
So, noisey brakes are either loose pads, caliper pistons not moving freely, air in the brake line, loose caliper installation (did you use locktite on the caliper bolts?) and a possible wave or warp on the rotor.
I doubt you over-tightened the caliper bolts although its best to have a torque wrench to measure ... a very good investment I must add!
I hope this helps.
Regards,
JohnMc
