uneven brake pad wear

[dmccormick]

Sorry, a couple more questions if I may. Eventually managed to get the other caliper holder off - cut two holes in the disc to be able to get it past the caliper holder and then sawed the retaining bolt off.

So the situation is that the rear right side is the one where one pad was down to the metal and the other only partly worn. The guide pins were free and the caliper piston has wound back OK.

The left side had stuck guide pins but the pads were even - in fact looked hardly worn. The caliper piston was very stiff and when I wound it back it has made a mess of the rubber seal:

I would have expected a stiff piston and pins to be on the same side where I got the really uneven pad wear, but it seems this is not the case so I',m puzzled why the right side had such uneven wear.

1) I obviously need to do something about the left caliper as it's now knackered. I see brakeparts do a caliper service kit - is it worth getting this and having a go at getting it moving or is that a really tedious job and I shouldd just fork out for a new caliper ?

2) If i replace the left caliper do you have to do the right at the same time like with discs/pads or does it not matter ? Is the right caliper suspect anyway because of the uneven pad wear ?

3) On the parts web site there are two different kinds of pad. One it says is for cast iron calipers and the other for alloy calipers. Mine are cast iron a(at least a magnet clings to them) and that tallies with the car's year and VIN number, but the pads that I took off look just like the ones for the alloy calipers. Is it possible someone fitted the wrong pads before and I should get the ones for cast iron calipers or is it more likely the pads I need are the alloy type ones ?

Once again thanks for all your help and advice.

 

[Burnerman]

Time for an exchange calliper I'm afraid - but the brake pipe connection is usually the banjo type so thats not too bad. The last one I did (Golf TDi 52 plate) was around £80. It came with a new banjo bolt and 2 washers.
So long as the pads fit the calliper and are the same size that came out, then worry ye not....I can't remember ever seeing an alloy calliper on these!
No need to fit a pair of callipers unless the braking / releasing effort isn't the same on both sides - the MOT test will sort that one later!
As for the uneven wear - anyones guess really....some discs have a chilled surface which is as hard as hell, yet on the other face can be soft.
Be lucky! Nearly there and a medal is in the post
John

 

[Mursal]

Would the other 3 pads have more resistance to movement (partially seized) when the brakes were applied, causing the remaining pad to wear excessively?

Don't leave the brake pipe disconnected/loose for long when you are changing over the caliper. Less likelihood of spongy pedal after you bleed out the air.

 

[dmccormick]

Just to complete the story, here is the finished job

I took the caliper bracket with the seized guide pin and sawn off mounting bolt to a local garage and for a fiver he got them out - the pin by drilling from the other side and hitting it out. He said not to worry about the hole left, just put a lot of grease in, but to be sure I tapped the hole he had drilled and fitted a short screw with threadlock to plug the gap.

Brakeparts in Rochdale did a caliper guide pin kit that came with new pins, rubber boots, caliper bolts and a tube of silicon grease so that was ideal as TPS Audi parts place didn't sell the guide pins on their own, only the whole caliper bracket assembly. TPS did supply the carrier mounting bolts though.

There were a few slight hiccups putting it all together, like I fitted the caliper bracket and torqued the bolts then realised I couldn't put the disc on with the bracket in place (that's why I'd had to saw the old one off in the first place, doh!).

Also, the ABS rotor just freewheeled on the new disc. It was only after I'd assembled everything with anti seize on the right bits, etc and fitted the tyre that I thought about it a bit more and realised the ABS ring probably should be locked to the disc. Had to pull it all apart and superglued the ring onto the disc then reassembled the whole lot and regreased the bearings.

The bearings were a nightmare to fit. In the end I put the housings in the freezer and heated the disc up and then was still bashing away with a club hammer and flat screwdriver to get them in. I imagine there's a good tool that does that much more easily or my local garage and another fiver, but by this time it was late Sat afternoon.

The only real issue is that I thought I'd be clever and use an Eazibleed to bleed the new caliper. 2 seconds later the brake fluid reservoir exploded so I now need to replace that. I later googled eazibleed, reservoir, audi explode and realised that I'm not the first person to do this . In the end I don't think I would have needed it anyway - I had filled the caliper with brake fluid before fitting and the brake pipe was still full of fluid and just by gravity bleeding the pedal is not spongy and the thing's working OK.

Road tested and all OK - whining noise gone and brakes working, wheel didn't fall off. Now I need to find a new reservoir and hopefully just prise the old one out and squeeze the new one in.

Thanks again for all your very useful advice and help.

 

[Burnerman]

Brilliant and very well done indeed
The reservoir is a push fit (with automatic fluid spill ) and best keep the Eesibleed below 20 psi - although these do bleed by gravity.
New reservoir on and top up (no pedal pressing) and all will be fine.
Quite a week for you!
John

 

[Mursal]

Great work, Audi workshop would have been expensive, you saved a small fortune.

 

[Agile]

I am also impressed by what you have managed to achieve!

Also by the amount of difficult to find small parts you have sourced!

Can anyone explain about the ABS part which you needed to superglue? That does not sound like a correct workshop procedure!

Tony

 

[Burnerman]

This ABS part is simply a toothed wheel (just like a gear wheel) that is fixed onto the driveshaft. A sensor close by can tell if the driveshaft is rotating by receiving a magnetic pulse from each gear tooth.
Its proper name is a reluctor ring.
Personally I've only replaced a couple of these....one ring simply pressed into place, the other needed heating up before being pushed on (a bit like a flywheel starter ring gear). I've no experience of gluing them in place.
Often enough, a replacement driveshaft is the way to go.
Not all ABS systems use a toothed wheel....on some cars, the magnetic pick up is actually on the wheel bearing ball race.
John

 

[mfarrow]

Not all ABS systems use a toothed wheel....

Some use a purely mechanical setup, but that's going back a couple of decades!

Good advice from John re. calipers. I've rebuilt them myself in the past thinking it must be easy. Fine if you've got the time and the patience but if it's seized it's usually due to piston corrosion and that plus the seal kit is about the same as a new caliper.

 

[Burnerman]

Mechanical stuff? That'll be the Ford belt drive system from the driveshafts...Escort RS Turbo etc
John

 

[dmccormick]

I am glad I listened to the advice on the calipers or I think I'd still have been at it on the Sunday and missed all the tennis !

For the ABS ring I was a bit worried about using superglue, but then I remembered that it was invented by NASA to hold the space shuttle heat protection tiles on, so it can probably cope with getting a bit hot !

For getting the parts I found GSF and Brakeparts very useful. Trafford Park TPS was a shambles - I'd gone there on Friday for the caliper carrier bolts, guide pins and caliper bolts; they said they would be there on Sat am. Sat am: they'd only ordered the carrier bolts and some bushes that I think are for the front calipers and the bolts hadn't even arrived ! That prompted a drive up to Rochdale to get the carrier slide pins and then to Stockport TPS to get the carrier bolts.

I also realised that my car had previously been fitted with the wrong brake pads - the ones for 97 onwards witlh alloy calipers.

Running smoothly now and the bonus is that the noise at speed is completely gone.

Next to tackle the viscous fan coupling which seems to be sticking....

 

[Mursal]

Mechanical stuff? That'll be the Ford belt drive system from the driveshafts...Escort RS Turbo etc
John

Way before my time ...................

 

[Agile]

I have been reading all this with interest because I have three Peugeots and my friend in France has a Fiat which is a rebadged pug 807.

There is no hayes manual for his Fiat because they only write one when there have been 100k vehicles sold of each model.

He recently had a sticking rear caliper which I diagnosed in france but we did not have the tools to repair it there so he waited until he returned to the UK.

As expected, the offside, outer, piston was seized but after soaking it still would not free up so not having had experience of these he took the caliper to his local garage where they freed it up and apparently quite easily as they did not charge him much!

Tony