Binding off side rear brake

[Buzzoff]

Hi guys

sorry for the long question.

ive an annoying issue I need advice with.

Ive a 2010 2.0l tdi 170 Scirocco.

I’ve uprated the front brakes to Scirocco R setup with no issues.

I Recently decided to upgraded the rears to Audi S3 rears (new brembo vented 310mm discs, Bosch pads and HEL Braided lines). I understand that Scirocco R,R32 &Audi S3 8P platform are the same and fit one another.
Initially while bedding in the rears over 400 miles I realised I was loosing MPG (approximately 5 to 10 mpg)I was at which point I realised the rears were binding and getting the disc hot.

I fully rebuilt the NSR ( older caliper which I bought missing carrier so I purchased a new TRW carrier)which was ok but originally stiff to wind in on original install.

I partially rebuilt Off Sid Rear caliper, seeing it was almost new eBay bargain.

Re installed all and bled the system. I even adjusted the handbrake cable off just a tad incase the handbrake was causing the issue.

After refitting the rebuilt calipers I Found that OSR caliper was still binding!!!

I decided to eliminate the OSR rear caliper completely and got a TRW exchange unit from Eurocar parts (Black Friday deal)...
As well as a new caliper carrier from Germany.

Ive just refitted all and it’s still binding....

ive disconnect the handbrake cable to eliminate that as an issue and after a drive it did nothing to elivate the caliper from binding.
With the car wheel jacked up the wheel spins freely with seemingly no difference to the opposite side..


Could the HEL braided line be bad? It was a brand new part.

Ive clocked up the disc using a DTI and it runs true to 0.01mm

Its pointing to a hydraulic issue which is not allowing the caliper to retract enough...

Before I replaced the original rear brakes everything worked with no issues.

Any advice would be greatly received.

Thanks

Buzz

[Buzzoff]

I’ve swapped out the HEL Braided line for the cars original flexi and it’s still binding...

As I’ve said previously the car was 100% fine with the original rear brake set up...

Any help will be very much appreciated

thanks

Buzz

[Crasher]

An odd one, have you done a system pressure bleed using diagnostic equipment?

[Buzzoff]

An odd one, have you done a system pressure bleed using diagnostic equipment?

Hi Crasher,

yes this has has been a real head scratcher for sure...

All of the lines have been bled through, but I’ve not got the diagnostic equipment for such check unfortunately.
My good friend (ex Audi master tech) said the VAG rear calipers are a real issue, I’ve no abs warning lights but he mentioned the remote possibility of the ABS unit being stuck on this particular brake line.

As I said before all was good before I fitted the new S3 setup...

Im going to refit the HEL braided line, re bleed it and take the car for another drive but get the abs to kick in on a quiet piece of road. Then if necessary undo the brake line before the flexi and see if it’s under abnormal pressure.?!.

I’m also considering swapping out all discs and pads, just to rule them out, I’ve spent enough a ECP recently, who knows it could be a rogue item?!?

I like to do as much as possible myself with help from my mechanic friends, I’m an engineer by trade so reasonably hands on.

Ive also a VAG Specialist local to me so maybe they could have the necessary equipment for the diagnostic equipment, would that be VCDS?

What do you think Crasher?

cheers

Buzz

[Crasher]

So with the back in the air, the brakes do not bind but the disc gets hot when driving?

Stupid question time, did you clamp the axle?

You have converted to 1KW spec at the rear from what I assume was Pr-1KS or 1KT? Pr-1KW on the Scirocco is perfectly acceptable as it was a factory option so the protocol is laid out and it uses calipers 8J0 625 423 E and 424 E with carriers 1K0 615 425 R left and 426 G right, the disc is 1K0 615 601 N and the pads 1K0 698 451 K. Now the interesting point is that the 1KS/T rear hoses were handed 1K0 611 775 D left and 1K0 611 776 right and 1KW hoses are the same each side and 1Q0 611 775 A changed to D in 2015. The difference is the 1KS/T hoses bolt into the caliper by banjo, the 1KW hoses use the pig tails so it could be that the banjo bolt is bottoming out in the caliper, which style of hoses are you using?

https://farm5.staticflickr.com/4854/44456147850_71eb217c93_k.jpg (https://flic.kr/p/2aJrnVL)

https://farm5.staticflickr.com/4855/46273011661_19f7fe5f90_k.jpg (https://flic.kr/p/2duZheT)

[Buzzoff]

Hi crasher thanks for your reply,

Yes when the car is in the air the rear wheels both spin freely, only whan the car is being driven does the Rear Left brake drags and causes the disc to heat up.

The rear hoses were replaced with Braided HEL items which can't be clamped.

The original rear calipers were not the banjo line type but the type that had another metal brake line (the same as in your second picture) on the caliper, so basically I was able to trial the original VW line (LH Rear Line) back on the real caliper.
This ruled out the HEL Line causing any issue.

I've no ABS/Traction warning lights on the dash so I'm hopeful that my ABS assembly is ok.

I'm investigating it again tonight, refitting the HEL Braided line and re-bleeding it, then going to test out ABS via a few heavy stops to envoke the ABS system...
I'll double check that there is nothing obstructing the hard lines at either end of where the HEL Brake line will be fitted..

The Discs and Pads I bought for my car were for a VW Scirocco R (which I understand are same as Audi S3 8P platform)
Looking on Mintex website for reference this confirmed the Discs and Pads are the same for these models.

If you have any more thoughts I'd be greatly apreciative.

Thanks

Buzz

[Buzzoff]

Update:

After double checking everything (making sure piston was retracting correctly), all looked good working order.
I re-fitted the HEL hose and bled the caliper again then took the car out and did repeated ABS inducing stops but alas the brake was still dragging...
My friend told me when he worked as an Audi Master Tech that the VAG rear brake design was always causing issues and he always had a 'good' spare rear caliper to test on customers cars...In this case my friend was happy with everything on the car and advised me to just drive it and it will bed in.

I decided to use my car on the necessary 150 mile (mainly motorway) round trip, I thought kill or cure!!!T
Thankfully my friend was right and it cured the dragging!!!:beerchug:

I hope that this thread will help someone else who finds themself in this frustrating position.

Thank you to you input Crasher

Have a great Christmas to everyone!!!