Jeep Cherokee (XJ, the real one) drum brakes Q

That's because the brakes aren't actually working when you're pulling on the cable. With the full force on that adjuster assy, AFTER the lever has moved the star wheel to compensate for worn shoes, and the shoes are squeezing the drum, the star wheel won't rotate back.

This of course assumes you are stepping on the brake pedal BEFORE you release the parking brake. Otherwise it would just move back and forth like you are doing with your hand.

GW

I'm not really seeing how pulling the cable (assuming it's done in the same plane as the shoe) is any different from the pull that it gets when the brakes are applied... the brakes are not self adjusting when driving either because they are way looser than when I adjusted them after install. I have deliberately stopped hard when e.g. backing out of a parking spot because I know the shoes will wear faster than normal until they're worn in.

Just wish I had a 100% correct vehicle sitting here so I could compare and figure out what parts are wrong, otherwise this could take a while... dealership is cool but pretty much everything will take a week to get, so it could take MONTHS to iteratively replace all the parts related to the self adjusters...

...or is this just a fundamentally defective design?

whole situation is a little perturbing as the last time I did a rebuild on self-adjusting drums I just bought parts from parts store, installed, and they worked (and I knew it right away as I could hear the self adjusters working while I pumped the brake pedal in the driveway.) That was back when this Heep was new though and on a '67 Dodge Dart...

nate

Copy of my last post to NAXJA:

I think I got it!

Sometimes I guess you just have to step back, pour yourself a cup of coffee, bitch on the internet for a while, and think about the issue before you actually come up with the solution.

The problem, I think, was that the new springs for the adjuster lever were too strong - not in the rotational direction, but they were pressing the lever too hard against the star wheel. I unhooked the spring from the lever, stuck my screwdriver in there, and pried it out away from the backing plate a little to bend it so that it would provide less tension in the "in" direction.

Pass side seems to be working now! I'll reinstall the new cable and guide so it stays working freely, then do the same treatment to the driver's side, and hopefully be done with this whole sordid mess.

(reference to "install new cable and guide" is because I'd started reinstalling old parts from before the brake job to see if any of the new components were the source of the issue. Apparently one was, but not one of the ones that I'd swapped out.)

nate

Correct. They are not self-adjusting when you are driving. Using the parking brake adjusts them. If you use the parking brake once a year like most suburbanites, it doesn't even work by the first time you set it, cuz the shoes are too far worn.

GW

No, they self adjust when you back up and stop hard. My point was that they were not self adjusting even then, but I figured it out as stated in my other post.

nate

don't you have to hit the parking brake when backing up to adjust them? I don't think just hitting your brakes does anything.

It may or may not help, not sure - but it's just a cable hooked at one end to the anchor pin, and at the other to the adjuster lever. So if the shoe-star wheel-shoe assembly rotates too far around the axle in the reverse direction before the leading shoe hits the anchor pin, it'll pull the adjuster lever and hopefully expand the star wheel a little (and then ratchet back to its starting position when the brakes are released, which is where I was having an issue with my setup after getting everything else squared away with the brakes.) There really doesn't appear to be any difference in how it would affect the self adjuster mechanism if the drums are expanded by the wheel cylinder or by the parking brake lever. The SA parts only attach to the anchor pin and the trailing shoe.

Apparently, based on a lot of comments on NAXJA, a lot of people haven't gotten them working on their vehicles and simply manually adjust the rear brakes at periodic intervals. Of course I consider a statement like that a challenge :) Most people seem to convert to rear discs from a Grand Cherokee or just swap in a Ford 8.8 rear from an Explorer, but I didn't feel like going through that hassle and expense...

I use the parking brake as a matter of principle anyway, having grown up in western PA...

nate

Old wives tale. When would a normal person even DO that?

GW

You have to use the PB. Correct

GW

When your brakes need adjustment?

Seriously, look at the way the thing is put together. The most cable pull will occur when brakes are applied in reverse - because the cable is hooked at one end to the anchor pin, and the adjuster lever is hooked to the (movable) secondary shoe. So when the vehicle is stopped in reverse, the primary shoe will rotate up into the anchor pin, while the secondary shoe will be pulled down away from it, giving the most cable pull on the adjuster lever of any condition likely to be encountered in normal operation.

that's been SOP for taking up slack in self adjusting drum brakes longer than I've been alive...

nate

Hardly. The procedure can easily be demonstrated even with the drum off on a leading shoe type servo brakes.

When would a normal person apply brakes while operating a vehicle in reverse? Could you possibly be serious?

That's exactly the description on page 6.1 of my 1963 Chevrolet shop manual. The 1965 book, page 5.1, says the improved brake design adjusts when braking forward or reverse. (we have a really nice library here)

I've never heard this described as phoney before. This brake adjustment procedure must be as old as drum brakes were around. Braking hard while in reverse might not fit into everybody's daily driving routine but neither is changing the oil or windshield wiper blades. This "tech" group has me worried.