Vw one rear brake disc hotter than other and abs error!?

Vw one rear brake disc hotter than other and abs error!?

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Discussion

strath44

Original Poster:

1,117 posts

93 months

Friday 26th July
quotequote all
Hi Folks,

I was topping up air in my tires and noticed that one rear disc seemed to feel hotter than then other side. Once home I grabbed an IR thermometer and one side was about 64 Degrees C and the other about 47 which is quite a big difference, the fronts were about 46 so I'm assuming thats about normal!?

The car is a 2012 Passat and it had new trw discs and pagid pads all round 3 months ago (5000 miles). Yesterday it came up with an abs error on that corner as well.

I bought an abs sensor and assuming it was a sticky caliper (the piston boot looked buckled) I rebuilt the caliper with new seals and piston, re-greased everything, fitted new anti rattle shims to the pad carrier and refitted everything and cleared the abs code. I also checked the wheel bearing for play etc and it was good.

Anyway drove to work today and checked the temp and its only 5 degrees lower ahhh! Any ideas at all?

One thing I noticed is it looks like the piston doesn't hit the pad square in the middle is that correct, it looks strange in the photo below but everything is square on the car, caliper, guide pins etc etc!!!

Any suggestions appreciated!





Edited by strath44 on Friday 26th July 12:48

GreenV8S

27,410 posts

229 months

Friday 26th July
quotequote all
You could check the other caliper to see whether that piston alignment is normal, but it's hard to imagine it could be wrong without some glaringly obvious problem.

Have you checked the handbrake mechanism?

ETA: Check tyre pressures too.

Edited by GreenV8S on Friday 26th July 13:31

E-bmw

5,072 posts

97 months

Friday 26th July
quotequote all
Your original findings weren't really significant.

20 or so degrees isn't really a lot with brakes as a one off measurement considering the discs can get to several hundred degrees on one stop.

Slowing on a sharp bend will produce more differential than that I would guess as each disc/caliper is effectively doing more/less of the overall task of braking to a stop.

50+ degrees I would potentially have been concerned about if it was always like that after differing scenarios.

Could just be a pad slightly closer, a bit less cooling through the disc, or any one of a few hundred different things.

Check it after every run for a few days/week & see what it is doing then.

strath44

Original Poster:

1,117 posts

93 months

Friday 26th July
quotequote all
E-bmw said:
Your original findings weren't really significant.

20 or so degrees isn't really a lot with brakes as a one off measurement considering the discs can get to several hundred degrees on one stop.

Slowing on a sharp bend will produce more differential than that I would guess as each disc/caliper is effectively doing more/less of the overall task of braking to a stop.

50+ degrees I would potentially have been concerned about if it was always like that after differing scenarios.

Could just be a pad slightly closer, a bit less cooling through the disc, or any one of a few hundred different things.

Check it after every run for a few days/week & see what it is doing then.
I would hardly say insignificant I’ve done at least 10, 50 mile commutes and it’s consistently higher each time.

Would a bad wheel bearing create that much heat?

stevemcs

3,324 posts

38 months

Friday 26th July
quotequote all
The wheel bearings on the Passat fail and throw up ABS codes.

tapkaJohnD

1,276 posts

149 months

Sunday 28th July
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Your Passat, like most moderns, has ESP, Electronic Stability Programme in its brake system. This will apply individual wheels' brakes to help correct loss of traction, due to overuse of throttle or road conditions. On the trip when you noticed the temp differential, it may have applied the brake on that side more than the other.
John