LouB

My A7 TDI Prestige with single piston front calipers developed a horrendous squeal when low speed braking at ~30k miles. I've been reading about various Tech Bulletins, etc. but figured this can't be too difficult to resolve.

Usually such noise indicates one (or more) brake pad(s) isn't moving completely away from the rotor when brake pressure is removed. (My understanding is that the [deformed] caliper seal and the rotor's inherent imperfection (not 100% true) provide this "function".) So either the pads were moving in the caliper (clips and/or glue hold them) or the pads themselves were hanging up on their pins. As shown below, it was the latter.


After removing the wheel:
1. Remove anti-rattle clip (thankfully this is made from stainless steel).





Rattle Clip Removal

2. Disconnect the pad thickness electrical connector (exists only on the driver's side; there is none on the passenger's side of vehicle)



Disc Pad Electrical Sensor Connector (driver's side only, none on passenger's side)

3. Cause caliper piston to retract into caliper. If it doesn't retract, then you've got bigger issues.



4. Remove caliper by removing (2) 14mm bolts and work it free. Then use some spare wire to hang the caliper away from the rotor rather than hanging it by its own brake hydraulic line.



One of two 14mm caliper bolts.

5. After blowing off loads of brake dust (I can't wait to replace these with Akebono's) you'll see the four corroded and crapped up brake pad pins. BTW- The inboard/outboard brake pads themselves were quite secure within the caliper.



The four corroded brake pad pins. (I can't figure why these weren't manufactured using stainless steel.)

6. Using some emory cloth cut to the desired width, I was able to clean up the corroded brake pad pins (although they were still pitted). Of course, one needs to also use some brake cleaner on all surfaces. Finally, I carefully applied SIL-GLYDE brake lubricant on the brake pad pins. Now the brake pads will be able to move smoothly on their pins.



Corroded brake pad pins cleaned and with SIL-GLYDE applied.

7. Finally, I reinstalled the caliper (used blue locktite on its (2) bolts... dunno exact factory torque requirement), installed anti-rattle clip, reconnected pad thickness sensor and finally the wheel/tire.

ABS didn't complain about anything and that damn squeal is finally gone!!!!
(Brake fluid level was fine.)

Hopefully this will aid a fellow Audi pilgrim and there is nothing unique here to an A7 (pictures depict my A7) except the use of non-stainless steel pins . In general, there are various slide/pin configurations on all disc brakes.

Cheers!
Lou in SC

tenspeed

Nice write up, Lou.

The front brake caliper to brake carrier bolt torque is 30 nm / 22 lb/ft.