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Parking/Emergency brake how it works and how to adjust it. - reversing and applying the brakes does not adjust it correctly, read on.

The following refers to the rear axle disc/drum assembly, and its based on a UK spec 4x4, however I don’t think there is any difference but the photos should give you a clue.

Before working on your vehicle please take safety seriously, do work on level ground, chock wheels, use axle stands and disconnect the battery if working near electrical components


Does yours look like the above.

The Nitro has a drum type parking brake system, the drum being formed inside a conventional disc brake. Often called a top hat design.

Even if you only want to adjust it and not strip anything down, the following should explain how it works, what to look for and where find them and maybe clear up some miss-conceptions.

The drum system is totally separate from the foot brake system, it is mechanical and cable operated, the drums are not self or auto adjusting and if working correctly the parking brake should be equally as efficient in either a forwards or rearwards direction. I’ll hopefully explain along the way, but I’m no robot and may have got it wrong.

I’ll take it the vehicle is safely off the ground with wheels off and the rear brake caliper and carrier assembly has been removed, this being covered in my part 1. pads removal.

At this stage I’ll also take it the disc came off easily but cover later the areas which may prevent this from actually being the case. When I first did our car one side was easy, came off no trouble the other was an absolute Pain in the ?^%$ to remove.

Once the disc/drum is off you can see the back plate and brake shoes, towards the front is the actual adjuster (red), towards the rear is the brake shoe Anchor, steady or fixed point, (silver colour) the part with the white arrow on it. This is fixed to the axle case and the part which takes the braking load and weight of the vehicle. At the side of which is the actual brake shoe expander mechanism operated by the cable.







In the ‘off’ position you should see both the top and bottom brake shoes resting on the Anchor fixed point, If there not, something’s wrong, find out why, most likely the expander or cable is partially seized, not returning to fully off and holding the shoes apart. The (red) adjuster at the forward end being used to expand the shoes to maintain the smallest clearance possible without binding, between the friction lining of the shoes and the drum.




When the brake is applied the cable operates the expander which as its name suggests expands the shoes, spreading the shoes off the anchor point into contact with the drum.




The expander is not fixed and is free to move on the back plate as is the adjuster.

So with the brake applied, the shoes are now expanded and locked to the drum, but in effect they can float on the back plate and if the drum turns the shoes will try and turn with it.

But the shoes can only rotate until a shoe contacts the anchor point. If the wheel turns forwards the lower shoe will contact the underside of the anchor and if the wheel turns rearwards the top shoe contacts the top part of the anchor.

There will be a slight amount of self servo action from the leading edge of the shoe into the drum but again as every thing can float this will also be same for both directions, just the leading and trailing edges of the shoe will reverse, So the brake works exactly the same in either direction and should be equally as efficient.

Not clearly visible, but there is an arrow stamped into the expander, this should be fitted the same way as the arrow on the back plate fixed point, so the expander lines up with its exit hole through the back plate to the cable, you will see it points up on one side and down on the other. Its not direction of travel, they are not left or right hand specific components there all the same just fitted opposite way round for the other side.




The main problem with the park brake is your usually stationary when you apply it, I’ve know some people with autos never use it and only use the gearbox ‘Park’. So the good part is it should never wear the friction linings, and therefore once adjusted if nothing wears should never need readjusting.

But its not all good, the actual result is the surface where the shoe lining touches the inside of the brake drum because there’s no actual friction taking place, corrodes, then when you do want the brake to work the shoes are being applied to a corroded uneven surface and not a smooth polished one, result the brake efficiency is poor to useless.




In normal service and its maybe a good idea to do it before you start dismantling anything. After taking all the safety precautions etc, it’s a good idea to occasionally apply the park brake whilst on the move just to keep things clean and polished. If you consider doing it, and I haven’t told you to, make your own decision. Don’t do it on a busy street, don’t do it at a stupid high speed and ‘do’ keep the lever ratchet button pressed in, travelling at something like 20/30 mph, just apply it enough to feel it working and slowing the car then release, your not trying to lock the wheels, if you do your tail lights may be come your front lights!!, try it a couple of times.

Back to the brake, when its applied, the amount you can rock or rotate the drum too and fro, is an indication of how well it’s adjusted, the better its adjusted the less movement there will be. Try rocking the wheel before you take it off and adjust anything just as a comparison for when you’ve done.

The adjuster is the ‘star’ wheel. The star wheel is like a nut turning on a bolt, turning the star wheel causes the bolt section to move and in effect lengthen the adjuster unit and therefore spread the brake shoes inside the drum. Both the left and right hand side brakes use a right hand thread adjuster. On the right side the star wheel is towards the top of the adjuster unit and on the left side it’s towards the bottom.

Why, well to adjust the brake without removing wheels etc, the star wheel is turned by inserting a screw driver or similar implement through an oval slot in the back plate. The slot is covered by a rubber plug and is to the front of the axle but to the rear of the caliper and its carrier, (the wire at the side of the slot is the ABS sensor wire)

Not easy to get at. And as you can see, you have to remember at one side the star wheel is at the top of the slot and the other it’s at the bottom.




But by doing this, to adjust up the brake, when you insert your screwdriver you move it in the same direction no matter which side your at. Insert the screw driver into the star wheel and move your hand towards the axle, turns the star wheel the right way to lengthen the adjuster unit.


With the drum off, To remove the adjuster unit first release the shoes from the back plate, the shoes are held to the back plate by a pin and spring clip (yellow) one at the top and one at the bottom, partially depress and slide the clip off the pin, you may have to reach behind the back plate and hold the pin as when you push on the clip you just push the pin through the back plate and don’t actually release it. Then spread the shoes against the single spring and the adjuster should drop out.

There’s not much to the adjuster, check the threads are clean and the star wheel is free to turn and lightly grease on reassembly.

Sorry have to continue with a part B thread as ive more photos to show, please save comments to end of Part B
Thanks.
 

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How To; Park/Emergency Drum Brake. Part B.

If you need to spread the shoes by inserting a bar or lever, be careful what you pry against, the ‘ABS’ sensor is fitted through a circular hole (Highlighted in white) behind the adjuster and is only plastic, held by a 10mm 'head' bolt it is easy to undue then pull the sensor out of harms way, the bolt may be tight all the way as it may have a lock-tight compound on the threads. The toothed (blue) ring behind the hub flange is the ABS exciter ring. Don’t hit it, bend it, or subject it to any other forms of abuse, The ABS and ECU’s wont like it and you’ll probably get a nice warning light illuminated on the dash.



To remove the shoes you have to fight the two springs at the expander end, one you see at the front face of the shoes and one behind.

If you have a suitable tool to unhook the springs from the shoes this is the easiest way but if you don’t you can lift the top shoe out of the anchor and rotate the shoe over the hub flange reducing the spring tension enough to release the large springs from the shoes.

You now have the expander unit still on the back plate, reach behind the back plate, pull the brake cable and simply un hook from the expander pull rod, the expander can now with a squeeze, come out between the fixed anchor point and the hub flange.

Check the expander is free, there isn’t much to it, remove the ‘E’ clip, clevis pin and it comes apart.



Clean the back plate, the white ‘X’ marks where the brake shoe rests on the back plate, check there are no wear ridges or corrosion at these areas and apply a light coat of grease.



If you have removed everything you will know what a pain the two large springs are.







The manual adjusters are both right hand threads,
(some cars use one left and one right hand adjuster).

The reassembly,
If you have a tool or a method for fitting the springs to the shoes whilst they are on the back plate, fine, fit the expander through the back plate, check arrow direction, then fit the shoes, the adjuster and the springs, finally the spring clips and pins to hold the shoes to the back plate.

If you haven’t such a tool for the springs the following can be done but its fiddly, may take a few attempts, and make sure there are no children within hearing range !!

Do not fit the expander first, leave it out, fit the large springs to the shoes whilst off the car, then fit the shoes and the springs together to the back plate, the springs will fit between the hub flange and the fixed anchor point, you can fit the smaller spring at the adjuster end, then spread the shoes at this end and fit the adjuster unit. Note which way up it goes for the star wheel.

At this point don’t fit the (yellow) clips and pins which hold the shoes to the back plate.

The brake looks complete but without the expander unit. You can not get the expander in with the shoes resting on the anchor point so lift the top shoe off the back plate anchor point and rest something like a 10mm thick nut under the shoe, now take your expander unit, remove the clevis pin from the expander which allows you to reduce its physical size then in its now slightley smaller component form, slide the expander unit in-between the brake shoes which you have got held apart, and between the hub flange and the anchor point. Make sure you have the arrows and therefore the expander the right way up for which ever side your working on then reassemble the expander between the shoes and refit the clevis pin and ‘E’ clip. Lift the top shoe and remove the Nut letting the shoe back down onto the fixed anchor and the expander at the same time.
It isn’t as bad as it sounds, and a doddle by the 15th attempt !!. (doddle-easy task, childs play, any undertaking that is easy to do)

Fit the spring clips and pins holding the shoes to the back plate.

Pull the brake cable and hook it back through the expander pull rod, thats the shoes refitted, now get your disc/drum.

Check inside the disc/drum and clean off 'if any' the corrosion ring which has probably built up between the outer edge and the brake shoe working area. The cleaner this area is the easier the next stage and adjustment will be.

Trial fit the disc/drum back over the brake shoes, then have an assistant apply the park brake lever a few times whilst you rotate the disc too and fro, or if on your own try pull the cable from behind the back plate, the purpose is to expand and centralise the shoes on the back plate in relation to the drum after they’ve just been disturbed, make sure the park lever is fully off and check the shoes are resting properly on the fixed anchor point .

Remove the disc/drum and turn the star wheel to adjust the brake, a small amount at a time till the disc/drum wont slide back on, (dont force or hammer it on) then move the star wheel back slightly. Fit the disc/drum and operate the park lever several times, again rotating the disc/drum to centralise the shoes, tapping the hub face of the disc with a hammer also assists here, remove and turn the star wheel one tooth try the disc/drum again, your aim is to just feel the shoes rubbing whilst you can still turn the drum, when you get to this point remove and the disc and back off the star wheel one tooth, refit the disc/drum. That’s about as good as your going to get without ending up with a binding brake and if done right you wont need to go under the car to readjust when the wheels are back on. Its not as fiddly as it sounds.



Right side, star wheel to top.



Note, you may have to angle screw driver to touch star wheel.



Above is the left brake, star wheel to bottom.

The more you can adjust before replacing the disc/drum the easier it is, as you can obviously see what your doing.This very much depends on how much of a corroded edge you have on the disc and how easily it will go over the shoes, if its too bad you have no option but to fit the disc then fiddle with the star wheel through the back plate hole, rather than being able to do it from the front without the disc on which is certainly much easier.

Apply the park brake lever, try to rotate the disc/drum too and fro there should be the smallest amount of movement, if you remember its as the shoes rotate with drum and contact the fixed anchor point.

Refit, the ABS sensor if removed, your callipers, wheels etc, and press the brake pedal several times before driving.

On the next few journeys occasionally apply the park brake as mentioned earlier to keep those polished surfaces in order. From the photos you can see there is 'no' connection between any rotating components (disc/drum) or the brake cables and the adjuster mechanism, the brake shoes are totally 100% manually adjusted by the star wheels.

Brake Cables and Lever
Two cables run the brakes to the lever, located under the centre console. the centre console has to be removed, (Disconnect Battery (neg) first and wait 10/20 mins),remove screws and lift console off over the park brake lever, to do this the lever must be applied to full travel, to do this you trick the system but need an assistant.

Chock wheels, release parking brake, under rear of car pull on the brake cable near the back of the drum, creating 'slack' in the cable,



Your pulling against the spring loaded lever auto adjuster.As you hold the cable ask assitant to apply the park lever as you release the slack, the lever will hopfully have come to full travel,The centre console can now be lifted forwards over the lever, when refitting the console you will have to pull the lever to full travel again, this time you can do it by pulling the cable on the lever drum. the next time you release and reapply the lever all will be back to normal.

The cables go through the floorpan under the back seat to a compensator and level assembly.







The cables stretch over time, this should be taken care of by the spring/drum unit in the lever. When you pull the brake lever you actually rotate a square section spring which tightens and grips around a drum, this in turn as you pull the lever pulls the single cable and on to the compensator.

It is this 'Lever' unit which has been recalled and replaced on some models as there is too much lever movment before actually pulling the cables.result excessive travel.





The excessive travel and poor spring operation can be improved as shown in another thread by slightly bending the spring rest/tag.

If you need to remove the cables or the lever assembly, first take up the spring tension and lock the spring drum, Easy to do, pull the cable and rotate the spring drum as in the photo then insert a screw driver or similar through the provided bracket into a slot in the drum This will stop the spring turning and pulling the cable, you can then easily unclip the cables from the compensator.





So as some have mentioned how does reversing and applying the brake lever adjust the brake, I’ve no idea. mechanically it cant, theres no conection but It obviously does something for some as many have stated so on the forum, but it cannot adjust the brake shoes in the rear wheel drum, the star wheels.

The lever is however auto adjusting the cable, every time you release and reapply, when in the off position the spring around the cable drum partially releases, there is another spring like a clock spring (darkest grey/black colour in the photo) which keeps some tension on the cables then when you pull up on the lever again the system should take a fresh hold on the cable drum, its possible reversing and applying the brake may coincidently be aligning the shoes, the expander or any moving parts which are a bit stiff inthe brake assembly so the cable doesn’t return as much, the lever then doesn’t have to pull the cable as far because it isn’t returning fully.

If it works it works, but I can’t help thinking it’s short term and maybe masking a problem which may develop further, it certainly isnt physically adjusting anything.

Please check out my other brake how to, How To:Brake Pads/Disc Change

Hope this has been useful
Keith
 

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Khaki Nitro Nut
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Well done Keith! Great write up and the Pics make it easy to follow.
:rep:
 

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WoW :SHOCKED: this is an awesome and invaluable tutorial, I know I will be referencing back to it. thanks :rep:
 

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Discussion Starter #5
Thanks, hope it makes sense as as long as it is, I still took alot out to shorten it
and have loads of phots left, thanks who ever linked the two A+B together, couldnt think of how else to do it.
just note yours will not be the same 'colour' !!! my wife thinks im mad paining bits you cant see.
Keith.
 

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Keith if it is not not much to ask, if you can put all the photos in this thread or another in chronological order that would be great. I know dealing with the rear braking system is a bitach :D
 

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Discussion Starter #7
I have added a couple more, but dont want to get repetative, I think in conjunction with photos also shown in my fitting pads/disc 'how to', its all covered.
unless some one has a specific question I could assist with, (maybe)
Keith
 

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WOW dude, that was one hellava write up and that parking brake system. :rep:
 

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Great job! Now if I can just figure which way to turn the star wheels, in the right direction, the first time, for once in my life! ...Let's see, my hand moves toward the axle... DOH!

I also need an English to American dictionary!! :chuckle:

doddle - an easy task
child's play, cinch, duck soup, piece of cake, pushover, breeze, walkover, picnic, snap - any undertaking that is easy to do

Got it!!:smileup:
 

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Discussion Starter #13 (Edited)
Just Hope its assisted some of you,

English to American dictionary, now that might be use full.
i tried to use a few i'd heard of but still cant get my head round some of your US terms/names
the only trunk I was aware of is at the front of an Elephant. :chuckle:

(markH) hope you dont mind ive added the meaning of doddle to the howto,
must admit never even thought about the translation bit for that one!!!!!!
Im sure you can suss out twiddle.

hope youve checked out my other how to - change pads/disc, as they go well together with this one i think.

Keith,
 

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The origin of "trunk" makes sense... but only if it's made from "boot" leather! :wave:


 

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There was a recall on the parking brake because of some sort of part that was bending and causing the brakes not to hold tightly (I don't recall which part it was). We took ours in and had the recall repair done, but ours never has held very well. I looked all over for an adjustment on the cable and didn't find one, so I'm going to be doing the adjustment on the shoes as well. Thanks for the pics. I had been under mine and couldn't find/see the access for the adjuster.
 

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Do you know the Recall ID# or TSB#?
 

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Discussion Starter #19
Depending on where you live. (climate) and how you use the park brake, if the lever doesnt come to full travel, the poor efficiency is often corroded inner surface of the disc/drum, which untill this is cleaned off, adjustment may not make much difference.

Try pulling the brake on slightly whilst on the move to polish things up before adjusting, but TAKE CARE when doing it, read the full how to,
regards
Keith.
 
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