Brakes: XC90 rear o/s brake binding

[Mikefo27]

Has anyone come across this before. Its a 2011 D5 200 AWD.

O/s rear brake caliper is binding against disc, not enough to notice driving but enough to heat up the disc to very hot on a motorway run. I started by making sure pads move ok in caliper and mount bracket - they do. I've replaced caliper with new caliper and also rear brake hose with new just to discount this. still binding. I've blanked off the ABS valve for that wheel and rear brake is now totally free, no binding for any distance without heating up disc. Proves its not park brake also! So it must be something from ABS module to the master cylinder but which one? Assume ABS module as master cyl only provides 2 pipes to ABS module so would affect more than one brake. i.e split circuit front o/s rear n/s etc

So i then replace the ABS valve and motor but keep the electronics so i don't have to get them reprogrammed. Still exactly the same, no change.

I'm currently going to swap the 2 rear brake pipes over but as they are different (one M12 other M10 sizes) its going to take me time to find the reducers. This will then show if N/S brake heats up which i think it will.

Is it likely the electronics now? i.e. trying to apply slight brake pressure due to faulty reading from abs ring or some kind of ESP system or something??

I would pull the ABS fuse but i'm worried it may cook the Haldex system? can anyone confirm this? Ps i've switched off Dstc for what its worth.

Any help would be greatly appreciated. Getting towards the end of my tether! Had car for 5 years + and its a belter! Apart from this.....

Cheers

[tonygreen1966]

Hi,

You've done some good work there to rule out most causes. I had a similar problem and it turned out to be a faulty rear ABS ring, which is integrated into the rear wheel bearing. The DSTC uses the ABS to apply brakes automatically and that was what was happening. But I did have some ABS/DEM/DSTC fault codes. Do you have vida dice? Do you have any warning lights.

Good luck

[Mikefo27]

Thanks Tony, nice to find out i may be on the right track!

That was exactly my thought the abs ring but no warning lights which made me dismiss until now. I think i'm going to have to throw £75 at a hub to discount it, after all, the old girl has got 135k miles on anyway. Wish me luck getting the old bolts out if they are anything like VW hubs.....

No not got vida dice. My mates garage has a decent diagnostics but not vida but i'll pop round there once i switched the brake lines around to confirm what i thought and give it a scan. First Volvo i've had and didn't realise they are unconventional!

Car is about the age where corrosion in these areas start to come into play

I'll update when/if i ever fix it for anyone else with the same problem!

[Mikefo27]

Thanks for your private message itec, your advice will help once i get plugged in!