Brakes: Periodic scraping after all brake pads replacement

[AlvinC]

Hello all.

Advice at last MOT was that brakes would need to be changed before next check. Also, handbrake effiiciency was 16%. Shortly afterwards, light scraping sound from driver side front on braking was my motivation to get cracking. I changed the lot, handbrake shoes, rear and front pads and did a full flush. Changing the handbrake shoes was a nightmare but that's a story for another day.

I thought all was well after testing, but the day after, I noticed the light scraping sound was back and still on driver side front. Checked all the work, no metal on metal. It is very intermittent, and I have been trying to replicate the braking conditions to see what brings it on. Best gues is when I leave the foot on the pedal and it comes on just before stopping - disappears on pedal release.

When doing the work, I noticed there was a lot of air in the front lines. I'm wondering if it could be an issue with air in the ABS? Brakes are working fine, and as I said it's intermittnent but it;s just an annoyance. Also, as it is the same sound that was there before the change, I'm inclined to think that the brake pads (which were very worn) were not the cause of thw noise.

Much obliged for any advice.

Alvin

XC70 2006 Ocean Race D5 AWD

[MWMan]

Not sure if this is the same problem as yours, but just recently I changed all the discs and pads on my V70, and noticed a scraping sound when turning.
Took both wheels off and really cleaned the mating faces between the wheel and the hub and tried again. A little better, but still there.
Another look showed that the new disc was just touching the back plate slightly. I pushed a large screwdriver between the disc and the plate to move it off slightly and there has been no scraping since.

[AlvinC]

Originally Posted by MWMan

Not sure if this is the same problem as yours, but just recently I changed all the discs and pads on my V70, and noticed a scraping sound when turning.
Took both wheels off and really cleaned the mating faces between the wheel and the hub and tried again. A little better, but still there.
Another look showed that the new disc was just touching the back plate slightly. I pushed a large screwdriver between the disc and the plate to move it off slightly and there has been no scraping since.

Thanks NWMan. That was one of the first things I had checked as I had read that might be the culprit. As I hadn't changed the discs, only the pads, I did it just to be sure I hadn't bent it when removing/replacing the caliper but all was fine. Also, as noise was same as before, I don't think this was the issue.

Thanks for your help.

Alvin

[Simmy]

the scraping sound is more than likely the pad wearing to the disc if it has any wear on it the friction material shape can vary so its possible this is your problem give it a good few miles and report back if the noise has gone also check the anti rattle springs are fitted correctly

[stuart bowes]

When you removed calipers and changed the pads did you give the sliding pins a good wire brushing and regrease? Just wondering if maybe one of them is sticking slightly on occasion and not letting it return back freely

Also, probably not likely to be related but did you check the bearing is turning smoothly and no play

Can you replicate the noise with that corner jacked up and spinning the wheel? And then the same but with someone occasionally dabbing the brake

Is it only when running straight or does it have any relation to turning

[AlvinC]

In response to Stuart -

Everything was thoroughly cleaned and greased and the pins were polished on a wire brush on the bench grinder. Each wheel thoroughly checked and rotated before and after refitting calipers. The moise, when it appears, is always when driving straight.

In response to Simmy, the disc was in good shape and as I said the noise was appearing before and after the change. Rattle springs checked thoroughly as I had trouble with them before on a different car. Gave the car a thorough testing and bedding the day of the change because I had done the handbrake shoes as well.

By way of an update, I drove the car today and the ABS warning light came on right from the start of of an 80k journey. No evidence of noise when using the brakes at all. On the return jouney, the ABS warning did not come on, and the brakes were also perfect.

Suspect it might be ABS related so. I have VIDA and a DICE so I'll hook it up and read the error code from the earlier ABS warning. I understand that there are diagnostics/proceudres that can be done with VIDA for testing/burping the ABS system, so if anyone has any experience with this I would welcome your guidance.

Thanks for all your suggestions and comments to date.

Alvin

[Simmy]

iv never used vida for bleeding abs .but it will locate abs fault and tell if mechanical or sensor clear all old codes drive to recreate fault read new codes and dont forget to read off the delivery tab only not the initial state

[AlvinC]

Originally Posted by Simmy

iv never used vida for bleeding abs .but it will locate abs fault and tell if mechanical or sensor clear all old codes drive to recreate fault read new codes and dont forget to read off the delivery tab only not the initial state

Thanks Simmy.

Took a reading from VIDA. Initial and Delivery tabs showed error BCM-0012 - Left Front wheel senor. Faulty signal. Cleared the codes, drove the car, and checked again. As expected as the ABS light had not come on last cycle, the Delivery code was gone. There is a substitute value for this code and that is 'ABS module is blocked' - so I think I am correct narrowing it down to the ABS. The question now is what to do - full or targeted rebleed? Cracking the hoses leading in to the ABS unit?

Alvin

[Simmy]

be care full opening the abs unit or you may end up with more problems than you have .it would not do any harm to change the indicated sensor before considering the abs unit to see if the problem persists

[JoeNinety]

Check the condition of your ABS reluctor ring, this could have something stuck in it, or rust, that causes the scraping noise and the ABS fault...and check the positioning of the sensor.