Rear Pad extraction 164S 1991

[harvey alperin]

I finally investigated why the brake wear indicator light was lighting up sporadically on the dash. I pulled the calipers on the front and made an easy determination of the issue. The right front inside pad was so worn and crumbly that the sensor was just flopping around making contact. I then figured it prudent to inspect the rear pads as well. After removing the 2 bolts (as done in the front) the calipers do not want to separate.I attempted to push the piston back in with a large C clamp but it did not act like other brakes that I worked on in the past.

Can anyone explain the key elements involved in separating the parts in the rear caliper area? How does the handbrake cable play in to all of this?

Thanks,
Harv

[Richard2]

And, I bet the 164 drives and handles like no other car you've had before
To retract the piston on the rear caliper, you need to put pressure on the piston while turning it clockwise. Use your C clamp to put a little pressure on it, then very carefully, use vise grips to turn the piston. There is also a special tool to do this. If it doesn't turn fairly easily, it make be seized. These things are very difficult to repair if seized. It's best to get a rebuilt set if they are.

[harvey alperin]

Richard2,
Thanks for the informative response to my question. I just wanted to be
sure before starting to compress the piston. I believe it to be clockwise.

Thanks,
Harv

[Michael Smith]

The hand brake adjuster rod is a threaded rod inside the piston which is why you must turn the piston as well as pushing it inwards. The self adjuster mechanism turns the rod as the piston is pressed onto the disc face when the foot pedal is applied. This lengthens the rod inside the piston as the pad wears and takes up any clearance due to wear.

Failure of this mechanism is the number 1 cause of rear brake seizing, I've had it happen twice until my Italian mechanic reworked the internal sheet metal spring with his machinists ball peen hammer on the anvil side of his bench vice. It was a pleasure to watch some handcrafting by a skilled man. It has given no trouble since.

Unless you can find that level of skill it is wise to replace the entire caliper if there is any doubt about the efficacy of this mechanism. I paid for two premature and entire rear brake jobs before this issue was repaired.