A4 B9 rear brake pads/grinding noise

Dean Shirt

Registered User
Hi all, just had my car MOT’d at Audi Stoke. At the same time I had the brake fluid changed as recommended. On the visual check they advised the rear pads were 70% worn. I’m not replacing them yet. However Iv had the car about a week and it’s been fine but yesterday and today when I start the car in the morning the brakes sound like they are grinding? Kind of like the car has been sat for a while. The brakes feel very soft and spongy until I have broke a few times. It has done this twice. Iv driven the car for 40 mins. Left it to cool and my next journey it happened again. Any ideas? Also why would my rear pads wear quicker than my front? Both sets have never been changed? It’s a b9 a4 avant 2.0 tdi 190 sline thank you
 

stuart scott

Registered User
Is it an auto?my car has only 22000 on it and its had brakes all round ,my last s4 the back brakes wore out first i think we use the brakes more with the auto box
 

Dean Shirt

Registered User
Is it an auto?my car has only 22000 on it and its had brakes all round ,my last s4 the back brakes wore out first i think we use the brakes more with the auto box

Yes I have the auto box. Seems strange that doesn’t it. Thanks for the heads up! Seems strange the noise I’m getting though when it’s been sat for a few hours in the cold.


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spartacus68

Registered User
Did they mention anything about the rear discs? If there's a lip on the discs or excessive corrosion I'd change them too, as it seems false economy just to replace the pads. The brake fluid change doesn't involve any physical adjustment of the brakes, so a full brake dismantle always helps these things, lubricate and check the brake sliders, clean the caliper carrier edges, a little copper ease on the backs of the pads, etc.

At this time of year it's not unusual to get noisy brakes, with road grit, salt, moisture, especially from start-up.

It can be done by DIY mechanic with knowledge. You'll need VCDS to back off the electro-mechanical handbrake, then reset it once the rear pads are installed.
 

Dean Shirt

Registered User
Did they mention anything about the rear discs? If there's a lip on the discs or excessive corrosion I'd change them too, as it seems false economy just to replace the pads. The brake fluid change doesn't involve any physical adjustment of the brakes, so a full brake dismantle always helps these things, lubricate and check the brake sliders, clean the caliper carrier edges, a little copper ease on the backs of the pads, etc.

At this time of year it's not unusual to get noisy brakes, with road grit, salt, moisture, especially from start-up.

It can be done by DIY mechanic with knowledge. You'll need VCDS to back off the electro-mechanical handbrake, then reset it once the rear pads are installed.

Thank you very much for the detailed reply, much appreciated. Audi didn’t mention anything about the discs just that the rear pads are 70% wore. Iv checked the disc (just by hand) and they don’t feel that they have lipped. Not what I would think is a lip anyway. I just find it strange if it’s the actual pads causing the problem with them being 70% wore. I may just get them done and see where we are at. So strange how it has only just started happening. Is it possible to see if something is between the pad and the disc? Thanks


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Spearo

Registered User
Sure - you can get grit or a stone between the calliper and disk or disk and backing plate , but I my experience a stuck rock or something usually results in a terrible screeching noise !
could it be that the heat shield has been bent when the brakes were being bled and that they’re now lightly touching the disk? When warm they may deflect away from disk???
By tbe way you don’t need Vcds to release the Parking brake in order to change rear pads - you just need to remove the parking brake motor and back it off and reseat pads with an appropriate size torx bit.
 

spartacus68

Registered User
Good call on the heat shield touching the brake disc. Easy done. A small stone can lodge between the disc and the pad, apart from noise, then you may see scoring on the outside face of the disc. Run your fingers behind the disc too or a visual inspection with a torch.

You can jack up the rear of the car, chock off the front wheels, release the handbrake and rotate the road wheel. You may hear a slight scuff noise which is acceptable as the pads will always have some contact on the disc. Anything more, then it needs more investigation.

Regards Spearo's comment, yes can be done without VCDS, but I find it easier. There's even some folk that use a 12v battery and jumper leads to retract it.
 

Dean Shirt

Registered User
Good call on the heat shield touching the brake disc. Easy done. A small stone can lodge between the disc and the pad, apart from noise, then you may see scoring on the outside face of the disc. Run your fingers behind the disc too or a visual inspection with a torch.

You can jack up the rear of the car, chock off the front wheels, release the handbrake and rotate the road wheel. You may hear a slight scuff noise which is acceptable as the pads will always have some contact on the disc. Anything more, then it needs more investigation.

Regards Spearo's comment, yes can be done without VCDS, but I find it easier. There's even some folk that use a 12v battery and jumper leads to retract it.

Thank you both for this. I will do some investigating tomorrow! Thank you


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cuke2u

Registered User
If your car has been sat for a while there will be a build up of rust on the discs and this can make a noise. A few heavy braking stops might sort it out. Other than that the system has a process of lightly applying the brakes as part of it's maintenance which can also rid the discs of any contamination over time...
 
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