PJH

Are the slider pins on the HP2 calipers torx or allen head and what size is needed to remove them?

Thanks

ITGUY

On my HP2's they are torx 50.

PEH

Thanks for the information.

Can the slider pins be removed while the caliper is still mounted to the carrier? Is there enough room to get the torx and rachet in there?

ITGUY

I'm not sure the rotor can be removed without swinging the caliper out of the way by at least removing one of the big bolts and loosening the other. I do recall that it was close to being possible with the pads removed but looked like it would gouge up the rotor. Someone else here might have a more definitive answer.

Those caliper bolts ARE a big pain in the butt though, even with a breaker bar and 2-inch extension. Had to use a steel pipe to extend the breaker on 2 of those mothers! That was after smashing my fist into the concrete floor of the garage after the socket slipped off.

Discovered a completely un-attached torx bolt to the lower guide pin on the front/right last month when replacing the rotors. Also discovered an uneven buildup of debris on the otherwise flat mounting surface of the calipers where the outer pads mount. Check this area before you re-assemble.

Don't know if you'll have sufficient clearance for getting a socketed torx bit in there, but maybe at least at a slight angle...assuming you're able to remove the rotor. You might need to clear out the recess of the torx bolt with a stiff toothbrush or small wire brush first.

Johann2.7t

the 18mm bolts on my caliper came right off, that gives you enough room to slide the caliper back and forth to remove the pads then pop the whole thing off.

pretty easy.

SloopJohnB@mac.com

There is a third option, i.e., 'triple square' that is used on a lot of German cars.

Most likely a 10 or 12mm triple square.

PEH

I have removed the rotors in the past (3 years ago) to put slotted ones on with ceramic pads but do not recall greasing the slider pins. Caliper must be removed to remove the rotor but I just wanted to clean and grease the slider pins with minimum disassembly. Thats why I was asking if the slider pins were easily accessable and what size torx was required. I don't recall what the setup looks like being 3 years ago when I did the brake job. I have a HP2 caliper, driver's side, sticking and I believe the cause is a slider pin or pins hanging up requiring cleaning and lube.

Thanks for the information. I have a torx 50 so at least that's one less item to purchase.

SloopJohnB@mac.com

Generally no. Remove the caliper from the carrier and THEN remove the bolts.
While you're at it you might replace the rubber boots and caps. Often the lower one gets weakened by exposure to CV joint juice and the cap goes away....a new cap won't stay in the boot.

The sliding pin bolt has to be out to replace the boot.

The dealer will tell you the boot/cap is unobtainium..ECS has them both in OEM and Meyle. I had one tech tell me the parts guy at Audi will order the part/kit if you give him the number but he never got around to telling me the number so I got mine at ECS.

http://www.a4mods.com/index.php/page...errebuild.html

PEH

Examined the left front caliper and removed the pads. Slider pins operate perfectly. With the caliper mounted on the carrier the bottom piston is just about frozen and is near impossible to compress with a c clamp.

My options are rebuilding this caliper or purchasing a re-manufactured one from NAPA. At the NAPA website they list this caliper for the 2001 S4 and the 2001 A6 but the 4.2 version but not my 2001 2.7t. Don't these 3 models use the same HP2 caliper?

If I was to rebuild the current caliper I would need a triple square bit, unknown what size, and locate someone who sells a rebuilding kit.

I would prefer to just replace the current caliper with the re-manufactured one.

Could someone check the NAPA website and see if the caliper listed for the 4.2 A6 is what I require?

Thanks

SloopJohnB@mac.com

Before you get a new caliper I would try blowing out those pistons with compressed air and scuffing/sanding the cylinder bore. Put in new seal and dustboot and lube the piston with brake grease and reassemble. Chances are the piston will come out without having to completely remove the slider assembly. I haven't done an HP2 but the rears are also single piston (rather than opposing pistons...the HP2 are dual piston but effectively single piston design) and the pistons will come out without disassembling the sliders. ECS has slider caps/bushings and rebuild kits...you'll need only one set. Do BOTH pistons on the caliper. You don't have to rebuild the other HP2 caliper if the pads are wearing uniformly.