Hello All,

I know this is a 850 column, but I thought maybe some one my have an answer for me. I have a '99 XC with just over a 100,000 miles on it. The problem was, that after driving the car in stop and go traffic for several miles, you would hear a "crunching" noise comeing from the front brakes just as the car came to a complete stop. My independent shop diagnosed the rotors as warped and replaced them with Brembo rotors to save $$$ (at my request) and installed new Volvo pads. About a month later the same noise returned, again just as you brought the car to a complete stop (after driving in stop and go traffic). My shop replaced the Brembo rotors under warranty with another pair of Brembos. Again the noise went away for several weeks and returned again. The rotors were replaced again under warranty, and this time Volvo OEM rotors were installed. Again, after several weeks, the noise again returned. The pads are fine. Does anyone have any idea what is causing these rotors to warp prematurely? Thanks for all replies.

Hugh

So there have been three sets of rotors installed after the initial pad replacement. I know you say the mechanic replaced the pads with "Volvo" ones but maybe it's time to try something different?

Fixit2002

At my expense, I may ask that a new set of Volvo pads be installed. I confess, I have a "bias" for Volvo parts. Although not cheap, they do normally fit and work better than after market parts.

Hugh

Hello All,

Well, my independent mechanic had my car for a week and drove it several times, but could not duplicate the "crunching" noise I hear coming from the front brakes as I bring the car to a stop. He checked the pads, the rotors and the calipers (not stuck) and all of them were fine. He could find nothing mechanically wrong with the front brakes. In my initial post I said the rotors had been replaced 3 times. Each time the crunching noise went away for about a month and then returned. My independent shop replaced the rotors each time, under the belief they had become warped.

I have to explain further. Typically, with warped rotors you will experience a "pulsation" in the brake pedal. That was not the case with my car. All you heard as you applied the brakes and brought it to a stop, was a "crunching noise" coming from the brakes. There was not "pulsation" in the brake pedal. This noise only occured just before the car came to a complete stop. This "crunching" noise only develops after you have driven the car in stop and go traffic for several miles. You will not hear it initially when you start driving the car after it has been parked overnight. I know this problem is still present. I've told my garage that when I get the car back, I'll bring it into them immediately when the noise presents itself so they can hear it and experience it firsthand. I'm just hoping some one else has had this problem, so it can be diagnosed quickly and fixed. Thanks to all who replied. I'll let you know how this plays out.

Hugh

Wonder if your mechanic forgot to put the caliper retaining springs back on....that would allow the outside pad to just kind of drag on the outside of the rotor and the crunching could be the pad bieng pushed into place....not sure if your type volvo has the retaining clip though......

Gwen,

Idon't know either. But I'll ask him "politely" if it the brakes do have such springs and if they were re-installed.

Hugh

Could it be a wheel bearing? I had one go bad with an intermittant sound, but that sound was more of a high pitched variety. Just a thought as maybe a bearing has a flat spot that sticks and frees every so often. Good luck, it took me two+ years to get mine solved.

dnlars,

Thanks. I'll mention it to my mechanic. This is a "strange" noise. I know I'm not crazy. I'm heard this "noise" consistently.

Hugh

I can do the front brakes in about one hour for both.(you might want to give it a try). Generally if you can easily push the pistons back into the calipers, the calipers should be ok......If brand new rotors are warping, that can only be because the rotors are getting extremely hot....this would happen if your calipers are sticking, but I can't think of much else that would cause that kind of heat. Sometimes one type of pad will fit in the slots of a caliper and still be the wrong ones. I wonder if your shop is using the right pads. "Crunching" is a strange description for warping. Normally with warped rotors you get pulsing in the brake pedal. Ask your mechanic what torque he is using on the lug nuts.....

If you used volvo rotors and pads, you might want to go to the dealer next time and get a second opinion on what's going on....

Gwen,

Thanks. I'll follow up with my mechanic.

Hugh

Unless the lugnuts are put back on without regards to torque, rotors don't 'warp'. The brake pad material gets deposited on to the rotor, and if the deposit is not uniform, you will feel the brakes shudder.

I would find a nice back road in CT, if there are any left, and bed your pads and rotors in before going back to the shop.

http://www.stoptech.com/tech_info/wp_bedincontents.shtml

If you are limited to speed, use your left foot lightly to keep the pad on the rotor while getting up to speed. Remember, you want to get the rotor red hot and then cool off before you stop the car.

Klaus
--
Proud owner of a 220S. If I had more room, I would have more Volvos.

Klaus,

Thank you, I'll try your suggestion. You don't think this problem is anyway related to the fact this is an AWD vehicle?

Hugh

Nope.
--
Proud owner of a 220S. If I had more room, I would have more Volvos.

Are both rotors warping? Do you feel if they're warp or just hear a "crunch" when coming to a stop? If the mechanic hasn't tried flushihg the system w/ new brake fluid give that a try. With all those pads replaced the mechanic should have been able to tell if the calipers were sticking.

Fixit2002,

I'm not experiencing any vibration when I apply the brakes, strictly a "crunching" noise.

Hugh

Fixit2002,

You raise a good question about whether both rotors are becoming warped. I know both were replaced each time. I also have to say the "crunching" sound which has been identical each episode seems to be coming from both front rotors, not from one side only.

With regard to flushing the brake fluid, as I do on all my cars (two '96 850 wagons) I request that the brake fluid be flushed everytime the brakes are serviced, i.e. even if just the rear pads are being replace, please flush the system.

However, the car is going back in tomorrow, and I'll suggest the possibility the problem may be related to brake fluid. I've experienced this "crunching" noise on my two 850s every so often, but once the rotors were replaced, the noise went away for good. Thank you for your reply.

Hugh