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Inside the Rear Caliper of a B5 A4

Discussion in 'A4/S4 forum(B5 Chassis)' started by Steve_D, Mar 8, 2013.

  1. Steve_D
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    Steve_D Member

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    [Mar 8, 2013]
    The information i wanted with pics about the rear calipers and handbrake assembly was very limited so went into this somewhat blind.. other than seeing a great writeup of a B6 rear caliper setup... so thought i would just post a few pics here so you can see the grubbings for those that might or want to do this for themselves... maybe haha.

    So basically my troubles were, a sticking caliper. and the handbrake has some loose travel when applying it.
    Went to biggred.co.uk and ordered a repair kit.

    The offending caliper (and Hole in the Backbox!) for the beady eyed viewers

    DSCF1711.jpg

    So i didnt loose too much brake fluid, i put a plastic bag folded a few times under the cap of the reservoir.. i lost about a cap full in drips :)

    Splits in the Dust Boot
    DSCF1716.jpg

    DSCF1717.jpg

    No airlines necessary to take the piston out on the rears... just pump the handbrake mechanism, but wear goggles.. brake fluid WILL Squirt out in any direction once the boot comes out of its seat
    DSCF1718.jpg

    Take the spring off, the nut on the rear of the handbrake mechanism and pull off that plate under it, undo the star bolt and take off the other one.. it makes it easier to do before you open up the system and find yourself covered in brake fluid from waist to toe
    DSCF1720.jpg

    These were caked in dust/**** even inside the Dust boot seat.. i dont know the correct tool to do this, but i used a very narrow flat had screwdriver and cleaned it out.. all was smooth after and made the seal much better. I didnt take a picture of the circlip inside here, i forgot. Its under the fluid and is a real pain in the ass to shift out. Just be careful not to damage the smooth surface inside it can be done and this is not under load from the spring.. see the next pic
    DSCF1726.jpg

    I did not see any point in opening this up so left it in tact, but where the o-ring is gave that a good shine it was the cause of my sticking handbrake, the corrosion (very slight) was just enough to make it stiff in the hole and not return to the lowest point. I used some abrasive strips that is used to clean copper pipe (also useful for the tail pipe too!) :)
    DSCF1729.jpg

    You can see the scoring made, the oring makes the seal inside the housing so as long as you dont take too much off when smoothing this out you will be fine.
    DSCF1730.jpg

    DSCF1732.jpg

    Put it all back together, bled the system and the handbrake is working so smoothly now, it feels completely different. Dont get me wrong if you want just go and buy a new one... but since i have never taken one apart nor attempted to take and thing off the braking lines, it was more to learn something new and not just take off, put on.

    This was my method, some may frown on it, some may not and just laugh haa haa, but it worked for me and have a fully functional caliper and handbrake again! Also its not in great detail, but im tired lol
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  3. Bradderz_1988
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    Bradderz_1988 Dont replace it, Upgrade it !!

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    [Mar 9, 2013]
    Good right up !!

    Where did you source the seals, boots, pistons from etc ?? Im thinking of doing mine at some point.
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  4. PAULF
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    PAULF Active Member

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    [Mar 9, 2013]
    Very good write up!

    One thing I will say, I had to take one of mine apart, and found the mechanism in your 7th and 8th pics was damaged.
    This is part of the self-adjuster, so I bent the tabs back, removed the internals (some ball bearings and a spring), cleaned it up and refitted it. It worked fine - but would have been so much easier if I had these pics!
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  5. spartacus 68
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    spartacus 68 Active Member

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    [Mar 9, 2013]
    Excellent write up. Only thing I'd add, as I did the same job a couple of months ago is to add a smear of Lockheed red grease under the dust sleeve to add a little lubrication. In addition, I found putting some marine grease on the hanbrake spring before reassembly and a zip tie around the rubber grommet on the handbrake cable end keeps corrosion at bay, as the cable is prone to fraying.

    Oh and get some chemical metal on the hole on your exhaust back box! :yes:
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  6. Steve_D
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    Steve_D Member

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    [Mar 9, 2013]
    Hi Bradders, cheers fella. I got them from here Bigg Red
    Great Prices and only 2 days delivery (thats what it took for mine anyway)

    Heres what u get in 1 set for the £26

    DSCF1725.jpg

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    Last edited: Mar 9, 2013
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  7. Steve_D
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    Steve_D Member

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    [Mar 9, 2013]
    TBH The only reason i never took this piece apart was just time, it took me that much time to get the circlip out, daylight and needing the car the next day... plus i could see the corrosion on the bolted side was my main issue. Wish i did take it apart now so i could have seen the internals of it. But i do have the other side to do hehe

    Ohh, good point! i didnt put and grease under the sleeve, but i did on everything else on the outside.

    The cables are lines with a thin plastic coating... but good point! I will strap mine down later :)
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  8. Steve_D
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    Steve_D Member

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    [Mar 9, 2013]
    Just googled that chemical metal looks really good stuff, been trying to find something to put on it! so thanks fella.
    Ive got some Epoxy Putty in would that do the same job?
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  9. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Mar 9, 2013]
    i got as far as that circlip, then gave up.

    Would be interesting to see how you actually got the clip out!
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  10. Steve_D
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    Steve_D Member

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    [Mar 14, 2013]
    aragon, i will be doing the other side soon, so i will remember to take some pics of that part of the job lol.. its the more tedious and the reason most dont attempt im guessing...

    Will update as soon as i have got there again lol
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  11. spartacus 68
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    spartacus 68 Active Member

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    [Jul 27, 2014]
    I've just had to strip both rear calipers down (not internals) as the handbrake wasn't retracting (driver's side). Not great when you're on the west coast on holiday without your main tools, with a boat on tow! Re-greased handbrake mechanism, slider pins, etc. Anyone got a how-to for removing the circlip inside the caliper. Take it I will need a circlip tool?

    Plan to order the Bigg Red kit. It's the rubber seal behind the handbrake that's deteriorated.
    Last edited: Jul 27, 2014
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  12. spartacus 68
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    spartacus 68 Active Member

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    [Aug 10, 2014]
    Just attempted this job again. I'd stripped the rear brakes down when I was on holiday a couple of weeks ago, so most of the bolts played ball and came out without a struggle.

    Good news is the caliper can be dismantled with a little perseverance and a couple of improved tools. I used a screwdriver and bradle after I shaved some width off it with an angle grinder. The circlip tool is no use until the snap ring is further out of the caliper housing.

    I've just ordered a master cylinder snap ring tool (50mm ends, 90 degree right angle). Managed one side, but couldn't do the driver's side. Also purchased the Big Redd rebuild kit.

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    Last edited: Aug 10, 2014
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  13. spartacus 68
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    spartacus 68 Active Member

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    [Aug 10, 2014]
    This is the tool that will work as far as I'm aware.

    image.jpg
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  14. spartacus68
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    spartacus68 Member

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    [Aug 16, 2014]
    This is the right tool and the snap ring comes off in seconds. Worth doing it to replace the 'o' ring inside and lube the mechanism before rebuilding.

    image.jpg

    image.jpg
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