DEFINITIVE DIY Brake Guide

[Alex156]

Hi All,

I'm writing in relation to my 2006 3.0 A6 Allroad.  Time has come to change the rear discs and pads.  I've done this job countless times on other vehicles and am OK with the release of the EPB (I have VAGCOM) etc. but am hoping that someone can clarify the CORRECT procedure for this job, especially when it comes to pushing the caliper piston back.  

Now, most mechanics I speak to simply say, take the cap of the brake fluid reservoir and push the piston back, using a screwdriver or appropriate tool.  Now ordinarily that's what I'd have expected although when I last referred to a well know car repair manual (all be it for a different make/model) it stated that when pushing the piston back in it was ESSENTIAL that the hose be clamped and the bleed nipple opened.  It was stated that this was to ensure no seals were 'flipped' by the back-flow of fluid and so that none of the contaminated fluid from the caliper found it's way back into the system which could cause issues/damage to sensitive ABS components.

Can ANYONE clarify what is the correct procedure as it's driving me nuts not being able to find a definitive answer to this one?

Thanks,

Alex 

[Magnet]

Hello Alex,

Since you have done the job many times and got away with simply pushing the pistons back and displacing the fluid ‘in reverse’ then chances are you might continue to get way with no ill effects. However, the proper way would be as Mr. Haynes states, and disperse the ‘rejected’ fluid out through the bleed nipple, thereby taking away any chance of ill-doings by reversing fluid back into the system. You know it makes sense as Del used to say! 

Kind regards,

Gareth. (aka Anyone in your capitals) 

[Alex156]

Thanks for getting back to me. I have no problem with either method. I'll always do what is best/safest. I have just read so many posts saying under no circumstances clamp the brake hose...... Would it be advisable to just undo the bleed nipple when pushing piston back without clamping the hose? If I did do that would I also need to remove reservoir cap? 

[Magnet]

Hello Alex,

Do you have a proper brake hose clamp, as opposed to an often used ‘Molegrips’?

I would guess you do, since you have worked on brakes. I think the answer lies there, with the use of the correct tool, used in the correct manner. 

Kind regards,

Gareth. 

[Alex156]

Hi Gareth, 

Yes indeed, I have the bar type tool which you can only tighten by hand so as not to go to crazy. I think all things considered I'll clamp the hoses when doing the rear brakes but then install new hoses to be 100% safe as I'm guessing they're the originals on the car. I'll then flush the fluid for new and bleed etc.

Im coming across 2 different lengths of hoses for the rear (350mm / 323mm). Any idea which is correct and/or if it matters? 

Thanks, 

Alex