Ive bought a fair few different calipers in different states of disarray and tried to repair a fair few as well. Few things I've learnt:
-Reconned calipers can be fine. Ive used reconned rear calipers when my old ones seized (and mk5 calipers are bad for it, especially the rear ones). Buying on EBAY you have some degree of protection, especially with paypal as the seller must state the functional ability of the item and most will list reconned - as new or second hand but functional. I was able to claim my money back on a caliper that clearly wasnt functional using this argument as missold.
- S3/r32 calipers have a small section of hard brake pipe in them, both front and rear. GTI ones only have this hard pipe section on the rear calipers. Reconned calipers often dont come with this section (although they do tend to include the bleed screws). The rear hard pipe sections are interchangeable between gti and S3 calipers but you need a crow foot spanner as its very easy to damage these pipe sections as you remove them, especially if the caliper has ever seized or overheated. Buying old mk5 calipers for a £5 is often an easy way to get a replacement pipe as new can be pricey. The r32/s3 fronts are NOT compatible with your GTI lines. You need a new set of lines. If the caliper has no hardline section then you need to get an oring made up on the brake line along with a bolt and crush washer. I was able to arrange this over the phone with Hel brakelines and it cost me no extra, they are experienced with this but if you buy a standard r32 brake line from them it will be two female end peices, not with an o-ring on one end.
-Buying second hand in person you can see exactly whats needed and they often have the hardline section attached. The risk is that the calipers have been sticking or are damaged and thats why they are being sold.
-Look for the general state of the caliper.
- Repeated excessive heating will have damaged the paint. Dirty paint is likely just brake dust, whitened/missing paint may be heat related and a sign the caliper is not in good condition. This is not a given but can be a guide
- The rubber seal around the piston should be intact. If it isn't there is a chance the piston has become damaged by grit/dirt or that it has rusted. the piston can be repaired or replaced but the barrel that holds it, the main body of the caliper, is not replaceable so if it is badly scored or damaged the caliper will stick repeatedly. Brake repair kits are cheap and easily available, I'd recommend them for anyone repairing their own calipers. I use Bigg Red kits off ebay. Comes with new rubber boots and a cylinder with some grease. Some include slide pins as well.
- Check if carriers are included. If so check the slide pins. The boots should be intact and the pins straight. They are easy to replace but if one has bent and not been noticed it will have caused a sticky caliper and potential heat damage
- Price wise I'd look to pay 200-300 for a set of front calipers and carriers in reconned or good condition. Rear sets should cost less but tend to be rarer so often command a similar price. I found a beat up second hand set for £50 which i managed to recondition myself and so far theyve been fine for over 5k miles. I have also wrecked a caliper when I snapped a bleed screw off in it and made a hash of drilling it out. You win some you lose some.
-Discs and pads. Sometimes people sell them with the calipers as a package. They weigh an absolute tonne (345mm discs are at least 20kg for a set) so postage is often pricey. New is not extortionate so have a think if a half worn set of discs is worth it to you (and the seller) to get them posted.
-Fitting is easy. There are loads and loads of guides, I find micks garage and the pelican guides very informative as a place to start. Both, I think, are stickied on this forum. Be very, very careful of the hard lines in the chassis. Muck them up and your replacement brakes will get VERY expensive. Use the right tools (crows foot/brake spanner) and loads of release agent. MY car is 120k miles and 10 years old but a good spray of release agent, patience ( and a cup of tea) and they all came undone smoothly. You do not want to twist the hard lines as you cannot twist them back into the right shape and you dont want brakes failing on you.
Thats a fair old page of stuff I guess. Ive replaced and repaired my GTI brakes and then replaced and repaired r32 front and back so happy to offer help and advice where I can. I'm certainly not a pro though so if I have got anything wrong I hope people will point it out to me. You can save a vast amount of money with reconned calipers and still get a great set of brakes. You can also save a lot of money replacing your own brakes. My brother in law was quoted well over £850 for new discs and pads on his 7R recently, we did the work for nearly half as much and hes had no problems whatsoever.
