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Drivers side rear brake binding – 2007 UK, 2.0 tfsi, manual. How to diagnose

3K views 6 replies 3 participants last post by  RobSlaterFSI 
#1 · (Edited by Moderator)
Hi,

During the annual service at a local VW specialist a few items where picked up as needing attention. One of these as the rear driver’s side brake was slightly binding when the hand brake was released.

Approach

I think Vox has mentioned this a few times that an assessment of the job needs to be undertaken first, i.e. is this something that can be done at home safely and what investment do I need to make in terms of tools and time.

Not just doing the job, but time for research, fault diagnosing and picking up the required parts. Weather is also a key factor as to whether I would do the job myself. If this needed to be done in the middle of winter, I would have given the job to the garage to do as it’s just not practical to it do outside. Also factor in how long you can have the car off the road as the parts provided might not be the right ones.

Three trips to Eurocarparts to get the right once …..Arrrr

As the Eos isn’t our main daily driver and I have access to a drive way and it was warm enough to work outside, so I decided to pick this job up.

This isn’t a full write up, but more of an overview of my approach / fault finding process. As with most things a bit fiddly, and the caliper carrier bolts are a bit of a pain to get at, so its time consuming, but can be done at home. Time wise allow at least 2 hours per side, if you have the right parts. Hindsight is also a wonderful thing …

Symptoms

With the wheel jacked up, other wheels chocked and the car in gear, release the handbrake and spin the wheel. There should be no binding / rubbing sounds and the wheel should spin freely. Mine was making a slight ‘grinding sound’ as if the pad(s) was still in contact with the disc. All other wheels span freely with no problems.

The car isn’t used for many miles per year, and when driven after being laid up for a while (about a week) , a slight grinding sound could be heard from the rear for the first few miles. I had assumed it was some rust that was rubbed off after a few miles. Brake feel and performance was fine

Tools

Usual array / good set of tools / spanners etc.
1/2 inch breaker bar
½ inch Impact spline set (Clarke pro216 , machine mart, £22.00) You need the m14 spline to remove the caliper carrier bolts
Brake caliper re-wind tool – Don’t think about this job unless you have a one, around £15 - £20
Gunson eezibleed kit - makes to job some much easier

Investigation

1. Use jack stands / chock wheels , leave in gear and remove the wheel. Inspect all brake components for condition including the brake lines all the way back to the reservoir. Also check the level . All looked fine

2. Remove caliper bolts by holding the inner bolt and turning the outer, and hang up the caliper. Don’t let it hang down on the hose. Then and remove pads. Both pads looked fine, with an even amount of wear, the disc also looked fine , with a slight lip on the inside face towards the hub , as if the pad was not making full contact with the disk. see PIC_1. There was no evidence of overheating on the disc or pad

3. Inspect the caliper for leaks and conditions of the rubber boot . Clean with an old tooth brush to remove all muck / brake dust

4. Overall other than being mucky and need of the good clean and re-grease and a slight lip on the disc all looked fine / within spec , see PIC_2

5. The slider bolts were also moving fine , and the boots looked ok , i.e. no splits

6. Clean and re-grease parts as needed including the pad carriers , see PIC_3 which shows what grease I used

7. Clean the caliper carrier where the pad carrier sits . see PIC_4. Use a file to remove the rust etc.

8. Remove the reservoir cap. You may made need to remove some fluid as you need to push the caliper piston back and need to allow for this fluid to get pushed back into the reservoir

9. Use the re-wind tool (clock wise) to push the caliper piston back, this was very difficult to do , very stiff

10. Re-assemble , replace wheel press brake pedal a few times and test

11. Result , same problem

Conclusion
As the pad wear was even , and other than a slight lip on the inner surface of the disc all components were ok / within spec . Nothing really stood out as to the cause. The caliper did seem very stiff when pushing it back , but I didn’t have a frame of reference i.e. was the other side just as stiff.

After a bit more research / googling I undertook the following

1. With the wheel removed , release the handbrake cable , check the cable isn’t stuck, push caliper back in , reassemble and re-test

2. Same result , slight binding

3. Re-attach handbrake cable
This test was done to eliminate the handbrake as the cause

Next steps
At this point I had two options, replace the caliper leaving the pads and disk as is .

Thinking here was the caliper was not retracting when the brake pedal was released , hence the binding and disc and pads were in spec. As all other wheels were fine / no problems and VCDS didn’t report any problems I assumed that the other parts of the brake system were fine. Option two was to replace the disc and pads , re-test to see if the lip on the disc was the problem. If I still had the problem replace the caliper.

To try and confirm it was the caliper, I removed the caliper again , hooked up a bleed tube and pushed the caliper piston back with the bleed nipple open . Fluid should gush out and the piston move freely . Mine didn’t . At this point I suspected it was the caliper at fault, but not 100% sure

In the end I went with replace disc and pads , no improvement so replaced the caliper. I used Eurocarparts of this and it took three goes to get the right parts. The best option if not using the dealer / TPS is to take to parts with you if you have the option to check for size / fit . Remember to fit disc and pads in axle pairs i.e. if you replace one side you have to do the other to ensure even braking.

Caliper replacement (the hard bit)
1. To replace the disc you need to remove the caliper carrier . There are two bolts on the back of the hub and it’s only the carrier part that is threaded so it’s almost impossible to get penetrating fluid in as its blocked by the disk. A few people have said you can remove the disk with it in place but it wasn’t possible

2. Remove the wheel arch liner and mud flaps if fitted , this gives enough room to feed the socket and bar in . Some people have removed the bottom nut on the shock to get more room but I didn’t need to

3. Insert the socket and make sure its home and flush as these are tight and rusted in and you don’t want to snap the head off. Unfortunately, there isn’t enough room to get an impact gun in

4. PIC_5 shows the carrier removed and the bolt location, give these and the bolts and carrier a good clean , brass wire brush works a treat

5. The disc is held on by a single screw which once removed the disc should drop off , if not tap with a rubber hammer

6. Clean up the hub and smear the surface with copper grease. Just a little but make sure it’s even and spread out

7. Clamp off the rubber brake hose and remove the caliper

8. You need to pre bleed the caliper first , i.e. fill it with fluid, just attach a hose to the bleed nipple, open the nipple and pour in till it drips out the bottom.

9. I had the remove the metal pipe that connects the caliper to the rubber tube so this needs to be filled up as well ( as best you can) see pic_6
10. It’s a right pain to refit and I found that starting the thread on the caliper first then the hose , and then tighten up just a fraction on each one in term worked best

11. Clean your disk and refit

12. Refit carrier , 90 Nm + 90 degrees

13. Re-grease all moving parts and refits pads . I had to file the ears of the pad to make sure they moved freely, i.e. just file the paint off the ear a little until you get free / limited resistance in the holder

14. Bleed to brakes using a one man system . This is so much easier than get a helper to push the pedal. Top up fluid if needed pic_7

15. Check your work / torque / have a last look around

16. But a bin bag over the brake and refit the wheel arch liner / mud flap – this stops all the crud dropping on your new brakes

17. Replace brake disc and pads on the other side. As a side note the caliper piston was so much easier to push in compared to the other side

18. Refit wheel and reservoir cap

19. Start engine and press the brake pedal 7 / 8 times and make sure your get an increased resistance

20. Go for a test run to bed the brakes in , can take 100 / 200 miles of slow speed / slow braking / also check hand brake

21. Re-test after a few weeks and brakes are bed in to make sure the wheel spins freely

22. As a side note there is not point testing after refitting new disc and pads as they will slightly catch / bind until they bed in

Summary

Hindsight is a lovely thing, and it was difficult to get a confirmed diagnosis that it was just the caliper at fault. I think might have been able to get away with just replacing the caliper, but better safe than sorry . Remember The brake system is in two parts the wet side , brake fluid and grease , and the dry side , disc and pads and never should the two meet !

I did notice that a fair few bushes are on their last legs , so looks like these is the next job … Any one had a good at replacing the suspension bushes ?

Regards
 

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#3 ·
Thanks for a good write up. From memory the rear suspension parts are fairly straight forward. There is more room and not so much weight on the rear, I'd rather work on the simpler rear than the front. I've done rear springs, shocks and handbrake cable, but no bushes yet. No surprises in that job, everything comes away and drops down easily on to a jack.

I also bought a piston retractor tool after I struggled with needle nosed pliers trying to turn the piston. The tool is the way. The self adjuster thread is very coarse. One cause of uneveness can be the hand brake cable adjustment. I bought each new half cable seperately one OE the other aftermarket and there was a few mm difference in length but you can compensate using each side adjuster. In your case, disconnecting the handbrake cable should tell you if binding is still in the caliper or not? I've always thought the way caliper pistons work is odd because there's no return spring for the pistons. When brake pressure is removed there is often some contact with the disc, but it should never be binding, unless the disc is warped which can happen.

If the handbrake cable has been rubbing and got water inside it may stiffen up and not release the caliper arm. When you look at the cable routing you'ld expect cable friction both sides to be the same, but I always found one side would come on first? I think I always checked on one notch, then two that the hand brake pulled each side evenly, which is what they also check for on the mot brake tester.

When they mot brakes on the brake tester, their big meter dial can easily tell if there's uneveness and they will apply gentle foot pedal pressure whilst watching for any fluctuations. what this is telling them (& you) is if a piston on a multi piston caliper is partially seized or not or if for our type, one half of the caliper is jamming on the slider. The throat of the caliper where the pad slides in can be another place for sticking and I will clean off any hardened brake dust with a needle file.

If I remember correctly, the V.W rear calipers are those nasti cheap single piston sliding assembly type that are supposed to self center? They are one reason why I'd like to change the calipers and have more pots without the sliding gizmo. When fluid enters the caliper, both halves slide and in theory there should be the same pad contact pressure on each side. However, their system depends on the slider and groove on each half being clean without friction, clogged with brake dust and not sticking. Sticking can occur if the slider or groove gets worn. Although not in any brake service manual, I usually carefully clean up the slider and particularly the corners with a needle file, then add a very small amount of copper ease grease (I like that stuff a lot!). I've used the same on the self adjusting helix thread and the back of pads.

You seem to have had the same problems getting the right brake parts. Eurocarparts always offer me 2 or 3 different pad variants for my VIN and now I always record their catalogue part numbers and hold back a worn pad to use as a pattern for future reference.
 
#4 ·
Great how to Rob and nice to see you used the correct grease (ceramic) for the sliders as other greases can cause them to stick, again well done.

Mick


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#6 ·
I used a spring compressor eventually. I've been there before with spring compressors and have 2 or 3 different types because the coil spacing is quite narrow at the top and bottom I used the cheapo sort which is a threaded rod with longish hex nuts and fairly thin steel hooks welded on each long nut. The more expensive forged end type just didn't get in there. Having once had a spring go 'bang' and 'boing' in my vise I now take precautions to stop compressors sliding down the coils. I unscrew worm type hose clips and put them back each side of the compressor hooks to stop them sliding. It takes a little longer, but stops the spring exploding in your face. Whichever way, it is pretty easy once you get the rear end off the ground.

There's a VW Tech bulletin regarding rear noise produced from the springs in contact with the body. If the bottom lower spring plate is found to be galvanized 1K0512297C they recommend replacing them with a rubber version part 1K0512297D. At the time I had some sheet rubber around and made a mat to go under the lower spring plate. Looking at the VW photos of their modified part, I thought it was still a metal plate but just given a rubber coating?

You will be o.k on standard rear springs OE spec. from Eurocarparts. If yours is the EOS Sport, the front springs are thicker specials and must be OE spec. when all the Fleabay aftermarket parts sellers will sell you the standard EOS thinner springs! :eek:
 

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