Parking brake ineffective with adjustment screw full tight -97 SL1

[trottida]

Originally Posted by steve seibel

1) So I want to set the adjusters in the brake drums so that there is a *slight drag* on the brakes -- and this adjustment is made with the parking brake handle *down*, right?

Yes, back off the adjustment screw a bit and the parking brake should be fully down. Adjust the shoes using the star wheel till there is a slight drag when rotating the drum by hand.

Originally Posted by steve seibel

2) Doesn't this in essence mean the brakes are dragging when I'm driving? That's not a problem?

The brakes will drag at first and they will settle. Shouldn't be a problem to be concerned about.

Originally Posted by steve seibel

3) So, at present, I can't stop the car from rolling with the *parking brake*. There's *some* resistance to rolling, but I can still push the car. So what is stopping the handle from just rising a few inches higher-- a few clicks higher-- when I pull on it? It's nowhere near how high it can go if I set the adjustment nut to the full loose position. (It's in the full tight position now.) Is there something about the geometry of the cables from handle to the brake drums (thanks for the photo btw) that puts a limit on the total travel of the cable which is *independent* of whether or not the shoes are being pulled tightly against the drums, and also is *independent* of whether the handle mechanism has risen to the highest possible position that you would get with the adjuster nut full loose (all the way up)? Can someone explain how what that limit is?

Thanks--

I think the limitation is the length of the cable itself. It basically controls a leaver at the drum that compresses the brake shoes. The cable is at full stretch and it's still not enough to compress the shoes. As I understand it, you have to adjust the shoes to counter that.

If you have ever worked on a pedal bike with hand brakes (with cables not hydraulic) you can relate it to that. There is an adjustment at the hand brake to tighten the pads and when that adjustment is fully consumed you have to go to the brake pads themselves and shorten the cable length.

..

[steve seibel]

Ok one last question--

4) The parking brake handle is connected by cable to the brake adjustment mechanism. That's what appears to move the mechanism. So any method to attempt to adjust the brakes by driving a certain way (e.g. backing up and stepping on the brake pedal), that does not involve pulling on the parking brake handle at some point, can never change the adjustment of the brakes, or more specifically can never turn the adjusting wheel inside the brake drum, correct?

[billr]

Post some pictures of that brake stuff, both sides, with the drums off. Better yet. post videos showing how things move as you raise the hand-lever.

[steve seibel]

It's being suggested to me that if the parking brake cable is set too *tight* at the adjustment nut by the handle, then when the parking brake is pulled there might not be enough motion of the mechanism inside the brake drum to advance the little adjusting wheel.

I'm skeptical--

Is there any way this could happen, at least assuming the cable isn't adjusted so tight that the parking brake is actually dragging with the brake handle all the way down? (Which it doesn't, even with the adjustment nut screwed all the way down. And the handle does come up 5 to 7 clicks with a moderate pull, like the Haynes manual suggests.)

Or is that not a viable theory?

Will probably have the drums off again soon and will get some photos or videos--

Thanks--

[fetchitfido]

Probably not where the issue is: Adjusting at the handle: https://www.youtube.com/watch?v=NatVQFa5zdM
Probably where the issue is: Adjusting at the drum: https://youtu.be/FpxQN2esZnU?t=370

The other option, if the shoes & springs are in good shape and adjusted properly is the cables have lengthened from wear. Should be easy to find them as long as it's not a '91-'96 2dr with rear calipers.
You might be able to see where the load-leveler off the handle attaches to the p-brake cables with the handle shroud off, maybe it's bent or the cables are falling out (if you can't see then the console needs to come out if you want to check).

[trottida]

Originally Posted by steve seibel

Ok one last question--

4) The parking brake handle is connected by cable to the brake adjustment mechanism. That's what appears to move the mechanism. So any method to attempt to adjust the brakes by driving a certain way (e.g. backing up and stepping on the brake pedal), that does not involve pulling on the parking brake handle at some point, can never change the adjustment of the brakes, or more specifically can never turn the adjusting wheel inside the brake drum, correct?

I'm not sure I understand the question.

You've maxed out the cable adjustment that controls the length of cable between the parking brake handle to the parking brake connection at the rear brake. You can only make the adjustment using the star wheel adjustment now. The star wheel adjustment controls the amount of compression of the brake shoes.

The star wheel adjustment is supposed to self adjust when the car is reversed and the brake shoes are compressed (hydraulic force via brake pedal or parking brake lever). I'm not exactly sure how the mechanism works but the star wheel will rotate a few clicks to tighten and take up the slack in the drums. If the brakes are not well maintained the star wheel mechanism may not self adjust. Part of servicing the brake shoes is lubrication of the adjustment mechanism.

Here's some information I found....

BRAKE SHOE ADJUSTERS.- Brake shoe adjusters maintain correct drum-to-lining clearance, as the brake linings wear. Automatic brake shoe adjusters normally function when the brakes are applied with the vehicle moving in reverse. If there is too much lining clearance, the brake shoes move outward and rotate with the drum enough to operate the adjusting lever. This lengthens the adjusting mechanism, and the linings are moved closer to the brake drum, thereby maintaining the correct lining-to-drum clearance.
Many vehicles use a star wheel (screw) type brake shoe adjusting mechanism. This type consists of a star wheel (adjusting screw assembly), adjuster lever, adjuster spring, and an adjusting mechanism.

Link type- The link type self-adjusting system (fig. 7-13) uses solid linkage rods to connect the adjusting lever to the stationary anchor point. The two linkage rods, connected together by a bell crank that pivots on the secondary brake shoe, operate the adjuster. One rod attaches to the anchor point and the bell crank, while the other rod connects the bell crank and the adjusting lever. In this configuration. the self-adjuster works only in reverse direction. As the vehicle is backing up and the brakes are applied, the adjusting process is as follows:

1. The secondary, shoe moves away from the anchor because of the self-energizing action.

2. The pivot point of the bell crank is moved in the direction of rotation.

3. The lever moves up on the star wheel through the connection of the linkage. If enough clearance is available between the brake shoes and the drum, the lever will engage another tooth on the star wheel. As the brakes are released. the shoes retract and the return spring helps force the adjusting lever down, rotating the star wheel and expanding the adjusting screw to remove excess shoe-to-drum clearance.

Lever type- The lever type self-adjusting system (fig. 7-13) is similar to the link type, in that it operates in reverse direction only. While the link type system uses linkage rods to perform the adjusting process, the lever type uses a stamped metal lever to engage the star wheel and actuating link to connect to the anchor pin. The adjusting process is the same as the link type system.

I believe that the S Series uses a lever type mechanism fig 7-13

[billr]

Doesn't the S-series have the star-wheel at the top, just under the cylinder??? That would not be like any of those posted above.

Yes, I believe it is the "lever" type, as opposed to a cable or link/rod; but I fear there is going to be (further?) confusion referring to anything other than what the OP actually has.

I gotta ask... were both brakes ever apart at the same time, any chance the star-wheels were swapped from one side to the other? I think one is LH thread and the other is RH.

Once the drums are off, it should be fairly easy to check if the hand-lever/cable is working OK; that is the least complicated part of this system. But without removing the drums we will just keep wandering around in the weeds guessing.

[trottida]

Originally Posted by billr

Doesn't the S-series have the star-wheel at the top, just under the cylinder??? That would not be like any of those posted above.

Yes, this is just generic information on the conceptual working of the star wheel adjustment function. The concept is applicable to S Series however the diagrams are not.

This site has all the diagrams and procedures for the S Series drum brake including the Richpin video....

Brake Shoe Replacement

[trottida]

Originally Posted by trottida

There should be a plug in the backing plate that looks like one of the 2 options below. This is from a 97 parts listing however it is applicable to 1991 through 2002 S Series. I couldn't find a good picture of the backing plate itself to identify the access hole. The backing plate are part numbers 21013315 and 21013316.

Here is the diagram showing the backing plate. I just came across it.

[billr]

The link in reply #28 is very thorough, let's use it for reference.