B6 Passat Rear Pad Change

[BobTheRocker]

Ok, I've carried out a lot of research into this task and I have myself a VCDS to do it. One question I would like an answer to:

Many state a battery charger of 15 Amps or more must be connected to battery to prevent error messages.

Can I just retract/deploy the EPB motors using the VCDS with the engine running as in normal operation to prevent any errors? If not, why not.

Any help or theories appreciated

[martin1810]

No idear but VAG specifically state use of battery charger. I guess engine running might be ok. Just not recommended in a garage incase you gas yourself or accidently knock it into gear and kill someone.

[DSG4ME]

Martin, have you investigated the claims that you can change the pads like normal as long as you wind the motors back 1st and undo the bleed nipple when pushing the pistons back, I've seen two ppl quoting the method recently, have you heard or seen anything to back it up yet?

[martin1810]

The bleed nipple bit is miss leading. You need to do that anyway if you want the piston to push in easily. You can wind the motor back with a 12v supply easily. The killer is winding the motor forward to the correct place ready for the new pads. You can wind it forward until you see/feel the piston being pushed. Then refit the new pads and caliper. BUT this method assumes your new pads are the exact same thickness as VW originally intended. Now when the epb is applied the motors will wind forward, the controller will detect the current peak and switch off at the right spot. If the pads are slightly two thin, the motor will wind too much and the controller will have a fit because the current peak didn't happen at the right time. I guess alot of times this method will work fine but it will be a pain if it doesn't and the controller has a fit.

[BobTheRocker]

Thanks for your reply Martin, I've been thinking about this. Surely the following procedure would be effective.

1. Using VCDS with engine running, retract torque motors.
2. Switch engine off and replace rear pads.
3. Start engine and using VCDS deploy torque motors to parked position and run test.

Unless there is some sort of reset the EPB controller carries out when the engine/ignition is selected off I can't see how it would be any different to normal operation. (Unless VW know something we don't)

I understand the battery charger is there to prevent voltage/current flow drop off during retraction and more importantly the re-deployment and subsequent test (hence preventing a fault code) but surely the alternator with the engine running (as in normal operation) will have the same effect.

Any one have any luck using a similar method?

The reason I'm asking this is that I have a battery charger but it is only capable of delivering 7 amps, not the 15 required by some write ups I've read. This does make sense as I've seen through VCDS that the EPB controller requires approx 14 amps per motor to effectively set the Park Brake

[martin1810]

I have just double checked VW instructions for rear pad replacement. It does not mention battery charger anywhere. If you want a copy, send me an email address.

[harltech]

The electronic handbrake setup can be very tempramental and it is worth following the guide lines or you can cause your self all kinds of problems. If you have a battery charger of any kind it is worth sticking on.

I was doing a set of rear pads once and one of the lads took the computer off the car half way through the job and i spent the rest of the day trying to sort the problems it caused. (and that is in a VW dealership with the VAS5051)

Also Im not sure if you can wind the pistons back with the engine running.

[andy good]

I have done the Job without the laptop etc I left the handbrake off removed the wheels and disconnected the battery took the pads off and removed the motors then wound the piston back with a torx socket you can turn it with your fingers wind it all the way back then i pushed the piston back with a g clamp put the motors back on and the pads in etc then connect the battery and operate the handbrake it sets itself as the motors cut out when there is a specific current drain from the motor i did it this way and had no problem it sounds a long winded way but i found it really easy and the motor is only held on with two small torx bolts so if you would rather use a spanner than a laptop etc this is the way ,it certainly is the way for me you just have to twist the motors to align the teeth before you can bolt it on and pump the brake pedal a couple of times to take up any play job done hope this helps someone all the best Andy

[martin1810]

This is an excellent method but it relies on the new pads being same thickness as previous ones. If not the motors will run for a longer or shorter time than the controller expects and the system will have a fit. So just be aware that this could be a problem.

[andy good]

Ok martin thanks for the advice but i replaced the old worn pads with new ones so they were obviously different thicknesses and in my experience the motors did run longer on the first application to take up the excess travel but after that they ran as normal and have worked perfectly since I hope this helps im not a mechanic so im not sure but i thought the motors cut off on application of the brakes when the motor draws too much current ie when they stop turning then on release just run until the motor runs freely ie brakes off anyway that was my thoughts on the matter and it worked for me but i can only describe my experiences which was great for me as computers and car ecu,s im not very confident with .thanks for your reply though its good to have other thoughts on the matter then other people can make there own decision on how to tackle this over complicated handbrake system .All the best Andy

[martin1810]

Andy...I think your method is good. Sorry I didn't mean thickness of new pads vs old pads. I mean thickness of the original pads when new compared to the thickness of the new pads. The controller does switch off the motors at peak current but the ecu also seems to include some sort of "run-time error" monitoring. Say the original new pads were a total of 20 mm thick, the controller will be adapted to that 20mm (how long the motor should run). If you fit new different spec pads that are 18 mm thick, the controller is still adapted to 20mm so the motor will run longer than the 20 mm adaptation says it should. The controller then has a fit because something must be wrong. That's why I was warning about it. Your method works fine but every now and then a controller will have a "run-time" error and have a fit. This can result in trips to a dealer and even suggestions of new motors or a new controller. As long as all pad manufacturers stick to the VAG pad spec, your method is fine.

[andy good]

Thanks Martin Ill bear that in mind good luck Andy

[richiemac]

http://forums.vwvortex.com/showthread.php?3865092


Handy guide to reference off.............

[Peter D]

Did you open the bleed nipples when you pushed the pistons back. ? Regards Peter

[andy good]

No I didnt there was no need too thanks Andy

[Peter D]

So you have forced old contaminated fluid back up the pipe. It is always best practice to expell the surplus fluid. Do you know how much an ABS pump assembley costs. Regards Peter

[andy good]

Yes i pushed fluid back up the pipe it goes back and forth whenever you push the brake pedal it wasn't contaminated and I didn't force it, its also no older or more contaminated than any of the rest of the fluid in the system, no I don't know the cost of an ABS pump assembly or want to know as I don't need one, you asked me a question how I did the job and I replied if you want to release the bleed nipple go ahead Andy

[Peter D]

When was the fluid changed completely last. Often when you press pistons back the fluid that comes out is discoloured and has black swirl marks in it. These are caused by the rubbings of the hydraulic seals. There is very little movement of fluid, it is a change in pressure and a small movement of the piston. Do your self a favour next time and crack the bleed nipple open. I did not ask you how you did the job. Glad you finished the job. Next time you have the rears off bleed your rear brakes. Regards Peter

[dmcentire]

I have a 2008 B6 Passat wagon that I'm going to attempt a rear brake pad change this weekend. I'll go with these steps unless someone suggests otherwise:

1. Use VCD to somehow "retract" calipers to "service" position.
2. Remove wheel, remove one or two bolts holding system on rotor.
3. Not sure if those bolts are torx or hex, will find out soon enough.
4. Use a c-clamp to compress the caliper back to it's starting position.
5. The above will go slowly but that's what I've always done with other cars.
6. Grease back of new pads, install new pads.
7. Install brake system back on rotor with bolts, and replace wheel.
8. Start car and press on pedal a couple times to reset pad position.
9. Engage the electronic parking brake for testing purposes.

Is there a VAG step I need after the procedure in step #1?

Thanks for any input, and I'll post what I can afterwards for others to benefit.

If photos are desired someone mention it and I'll take photos of the steps.

Dennis McEntire

[Peter D]

Why not start your own thread this one was June last year.

Regards Peter

[Peter D]

Do you have the special tools to remove the bottom bolt of the caliper both on the LHS and RHS mounting. Do you have a manual for doing, this I suspect not from what you say. Regards Peter

[nick.king]

I have just double checked VW instructions for rear pad replacement. It does not mention battery charger anywhere. If you want a copy, send me an email address.

Hi, is it possible you can send me a copy? I've sent you a PM.

Thanks, Nick.