Rear Caliper Self-Adjustment

[PatTroy]

I've been digging around for a few days online and in the manuals I have and I can't seem to find anything about how the rear brakes self adjust.

I was told once that if they don't adjust from repeatedly engaging the parking brake handle, then they should adjust by coming to a stop in reverse... I have both a pretty low pedal and a pretty high parking brake lever...

I'm now learning that the pads have a nub on the back which supposedly interfaces with the slot in the piston. It is possible that I did not line-up the slot properly after rebuilding the calipers, but every piece of info I can find uses ambiguous language to describe the correct slot position after adjusting/rebuild. Is it vertical or horizontal relative to the ground plane with the caliper installed? Does the nub go in the slot?

Thanks in advance!

[DieselSpider]

When you apply the hand brake the clutch nut inside the brake piston will rotate on the threaded stud activated by the parking brake lever to take up any free play inside and adjust the piston outwards. If the brakes have not been flushed regulary or the hand brake seen regular use the clutch nut and its spring mechanism along with the threads on the activators stud can get pretty badly gummed up and even rust up so it not longer turns freely enough to self adjust. The slot is to screw the piston back down on the self adjuster stud and set it back to its starting position. It should be set so that you can slide the caliper over the pin on the back of the brake pad.

You need to remove the brake piston from the caliper and then the circlip that retains the adjuster clutch. Be carefull as there are small ball bearings inside the assembly that will roll off into the land of the lost if you don't have a pan or basin to catch them.

[131]

The slot is positioned so it can slide over the "nipple" on the pad, not likely you'll get the caliper fitted if it's not lined up properly. The nipple on the pad stops the piston rotating when the hand brake is used. There is a line machined in the piston face next to the slot, this line goes towards the bleed nipple.

To adjust the handbrake, pull it on, put your foot on the brake and hold while releasing the handbrake, this holds the piston out while the handbrake rod retracts, giving the adjustment mechanism the best chance of working. Keep in mind with the age of these vehicles, the chance of the adjustment mechanism working well is not good. Saying that, I rebuilt 2 calipers this afternoon and the piston internals were in very good condition, no rust or grime, corrosion or pitting, it made the job much easier, just cleaned them up and replaced o'rings and seals.

[klweimer]

I found the complex little self adjust mechanism inside the caliper pistons were completely rusted up on mine; after I spent a short lifetime trying to adjust the parking brake linkage. I have never seen anything on the self adjuster in any of my shop manuals. You have to physically remove the piston from the caliper to look down inside to see the mechanism. Because the brake fluid will hold water, I bet this happens to a lot of these. You can buy replacement pistons from all our normal suppliers, but they don't have the mechanism inside, just the piston that houses it. I don't think you can get the mechanism by itself (but I could be wrong, happens a lot). The answer was a brand new set of calipers from my buds at AR. Dropped them in and the e-brake adjusted up in like, 10 seconds! Some days, it's hard to beat new.
Kirk

[DieselSpider]

I found the complex little self adjust mechanism inside the caliper pistons were completely rusted up on mine; after I spent a short lifetime trying to adjust the parking brake linkage. I have never seen anything on the self adjuster in any of my shop manuals. You have to physically remove the piston from the caliper to look down inside to see the mechanism. Because the brake fluid will hold water, I bet this happens to a lot of these. You can buy replacement pistons from all our normal suppliers, but they don't have the mechanism inside, just the piston that houses it. I don't think you can get the mechanism by itself (but I could be wrong, happens a lot). The answer was a brand new set of calipers from my buds at AR. Dropped them in and the e-brake adjusted up in like, 10 seconds! Some days, it's hard to beat new.
Kirk

They clean up quite nicely and are a fairly simple spring clutch type deal like a engine valve rotator. Remove the clip, dump the parts out into some rust penetrant and flush them out with non-flamable brake cleaner before reassembling.

This is one reason why brake fluid needs to be flushed out and replaced every two years. This is even more critical on new cars especially those with the Bosch ABS Systems as the ABS Pumps and Control Valve units can become badly impacted by old brake fluid.