Hi Everyone,
I'm hoping someone can help me out, I'm in the missle of fitting new brake pads to the rear of a 99 audi A4. Im having real problems getting the caliper pistion to go back in. It seems to be stuck (I'm pretty sure its not seized as the piston will move back out from the pedal). It seems like Im missing something to make it retract. Handbrake is off and the bleed nipple open with fluid coming out.
Any suggestions would be gratefully recieved,
John
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I think I may have the answer, I think the pistons need to be turned clockwise to 'screw' them back in, something to do with the way the handbrake operates I think. Im just off to try it out.
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well Ive tried 'screwing' them back but it doesn't seem to be helping. Im fast running out of ideas....
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If it's any help I had to use a G-clamp to get them back in on my old Metro.
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The standard reference for doing this on a Boxster or 996 is at:
www.bombaydigital.com/boxster/projects/brakes/chan.../
where he says at step 4
Now the pads are free and clear. You can just lift them out. However, if you are going to immediately put the new pads in, you'll need to compress the pistons to make room for the new thicker pads. The easiest way to do this is use the old pads to push the pistons back into the caliper. A simple technique I use is to simply stick a screwdriver or other prying device into the retaining pin hole in the pad backing plate, and pry the pad, as in figure H, to squeeze the pad back against the pistons. The point of this is to push the pistons back into the caliper so that the newer, thicker pads have room to slip into place where there is currently only room for a worn, thinner pad. Alternatively, you can buy a "pad spreader" for about $10 at an auto parts store (I saw one at Sears) that inserts between the pads and works like a reverse vise. You could also use pliers to grab the backing plate and caliper where the retaining pin holes line up, and squeeze them together, using a rag to protect the caliper surface from getting scratched up.
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as chris says, use a g-clamp. only a few quid at wilkinsons.
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Try slipping the old pads back in and levering between the pad and the disc with a big screwdriver, trying not to damage the disc and trying to keep the piston square in the caliper bore.
Levering without the old pad in place may push the piston sideways and jam it in the bore. Of course there is no need to worry about damaging the old pad.
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Lud - you beat me to it!
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ooo, i have done that a few times
i wonder if you have cut your hand yet doing it
gently prize it back with a big screwdriver, taking time of course for it to slip and you graze your knuckles
good luck
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Agree with the above. Also see if you can get a pair of waterpump pliers around the pad and the back of the caliper body.
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Many thanks to everyone for the suggestions so far - I've tried all the brute force methods I can think of - large screwdrivers, g-clamps (it broke under the strain).
Despite all of this the piston has not moved so much as a millimetre!
Looks like I'll be getting the train to work tomorrow!
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I've just found this posted on another website, I think this must be the problem (my pads were down to the metal). Looks like I may have to keep trying.
"One thing to note over and above Dave's instructions for the rear pads is that if your rear pads are well worn, the pistons will have come far enough out of the cylinders to have come off the handbrake adjustment threads. This increases the difficulty of getting the pistons back into the cylinders tremendously
If the pistons are out past the ends of the threads, you'll have to push & turn & turn & push until you luck out and get the pistons to engage in the threads! Once they're back in the threads they go back in pretty quickly, with only 2-3 of turns to retract fully. In other words, if you're wondering if the pistons went in a little bit or not on the last turn, the chances are they didn't!"
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I have an AUDI A80(1994)and to change the rear pads, I needed a Brake wind-back tool (Sykes-Pickavant from Halfords)to wind the pistons back into the caliphers before the new pads could be inserted.I think you may need the same tool.
Bill
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If you use brute force without a windback tool you will damage the thread they wind out on. The tools are now about a tenner so go and see if your model is listed then you will know as you clearly do not have or have not read your manual. Regards Peter
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I've been up to my local spares place (by push bike!) and bought a wind back tool. As per Peter's post I think I've damaged the thread as it still refuses to go back. It feels like it 'bites' on the thread but isnt catching properly. I guess my next step is to dismantle the caliper to see what damage I've done :(
Oh well, live and learn I suppose...
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No try the other side first using the tool. The pot should not have screwed right out so you comment about not catching is a little odd. Clearly your model was listed as having wind back calipers but how is the hang brake ajustment released on your car. Is your wing back left hand or right hand threaded. Easy mistake with you head under the wing. Take care, don't pop the cylinder out just jet as you may not be able to get replacement seals. Regards Peter
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Top marks and many thanks to Peter and everyone else who offered suggestions.
I have now fixed it!
I had one last go before calling it a day and I tried turning the piston anticlockwise, this made it come out further still, but then after some vigorous twisting back and forth it suddenly freed up. Once free it easily turned (clockwise) and wound itself back in with out any pressure needed.
Thanks again,
John
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It implies the seal was was an unused area of the cylinder and as such put up a lot of resistance. Hopefully no seal damage was done but do keep an eye on the fluid level and the disc's in case a seal leaks. Is you hand brake OK it will take a while to settle in. Do not overbrake to try and bed them in as you will over heat the disc's and glaze the pads. Brake hard and short for a few days and all will be well. Was your fluid due to be changed. ?? Regards Peter
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