Simon's new Xantia V6 and Leaf blog

[Mandrake]

I've done a bit of reading on it tonight, one thing suggested is a build up of lining dust in the mechanism which in very wet conditions can clump together as a sticky mess and cause binding in the mechanism (and it has been very wet lately!) also lack of lubrication between the sides of the shoes and the backing plate contact points or groves worn into the backing plate contact points.

I've only ever owned two cars with drum brakes and only one of those needed attention - and that was nearly 20 years ago... so if I did know anything about drum brakes at the time I've forgotten it now.

A strip down, clean with spray degreaser and reassembly with copper grease in the right places like the backing plate contact points might be all it needs. Weather is looking ok this weekend (cold but clear) so I'll get onto these drums asap while I wait for the rest of the bits for the front discs.

[white exec]

Drum brakes can have a self-adjusting mechanism, which works like a ratchet and takes up slack/clearances as the linings wear. This mechanism can get bunged up with dust and dirt, or just go dry, and it also needs setting up according to the book when shoes are replaced or refitted.

Handbrake cables which act on the same drum brake shoes also need setting up properly, to prevent binding. There can be an equalising mechanism which ensures the (two) hand brake cables do their job equally.

On brake vacuum, it was common for upmarket cars to have a small vacuum tank (about 4 litres) included in the system, to provide a reservoir/backup of vacuum for heavy braking or emergencies.

[Mandrake]

Drum brakes can have a self-adjusting mechanism, which works like a ratchet and takes up slack/clearances as the linings wear. This mechanism can get bunged up with dust and dirt, or just go dry, and it also needs setting up according to the book when shoes are replaced or refitted.

Handbrake cables which act on the same drum brake shoes also need setting up properly, to prevent binding. There can be an equalising mechanism which ensures the (two) hand brake cables do their job equally.

Thanks - its looking like it will be fine this weekend (but very chilly!) so I'll get out and have a look inside the drums. Hopefully a bit of cleaning up, lubricating and adjusting will do the trick without requiring any parts, although those are available if I need them.

This morning I tried the handbrake again while rolling slowly and the rear left drum was squealing and had a sound of metal to metal dragging while the hand brake was pulled on, and I could tell it was trying to grab and lock while the rear right wasn't. After 2-3 hard, brief applications of the hand brake while rolling this squealing/dragging sound went away and both rear drums seemed to pull on evenly and smoothly, albeit not particularly strongly. (although I wouldn't expect a rear drum hand brake to be particularly good when moving compared to the front disc hand brake on a Xantia, which is excellent!)

Does that give any clues ? I wonder if the leading shoe is not retracting properly due to some muck on the pivots and that is causing it to dig in, and a few hard applications temporarily frees it ? I'll certainly look at the left hand one first as that seems to be the one misbehaving.

Is copper grease suitable for lubricating the ratchet, pivots and backing plate supports for the shoes - basically everything apart from the rubber near the cylinder ?

On brake vacuum, it was common for upmarket cars to have a small vacuum tank (about 4 litres) included in the system, to provide a reservoir/backup of vacuum for heavy braking or emergencies.

I don't think there is any separate reservoir on this - I think the only reservoir is in the master cylinder itself. The vacuum pump (electric of course) is in the back by the main motor, the system seems to have enough vacuum for about 5 full applications of the brake pedal (with the key off) before the pedal gets hard, although after doing that and turning the key on it takes about 5 seconds for the pump to fully restore the vacuum, so it's not a high delivery pump.

Back when I first got the car the brakes did seem to work very well though and were nice and responsive, so I'm hoping by the time I've done both front and rear brakes everything will be tickety boo again!

[bobins]

If yours are 'wheelbearing-in-drum' then you might want to check you're not supposed to replace the bearing on refitting the drum....... though that step is - not surprisingly - often missed out

[Mandrake]

If yours are 'wheelbearing-in-drum' then you might want to check you're not supposed to replace the bearing on refitting the drum....... though that step is - not surprisingly - often missed out

Haven't heard of that before... although I have little experience with drum brakes. How would I know ? Can you tell from this ?

[white exec]

On our Toyota (disc brakes all round, but rear discs have incorporated drums as well, for parking brakes), there is a definite parking brake shoe adjustment procedure, which says that the adjuster should be turned (through a hole in the drum) until the shoes contact the drum (and it can't be turned), and then backed off by eight notches.

Wouldn't be surprised if Mitsi were something similar. Haynes is usually pretty good on this sort of thing, which makes a nice change.

[bobins]

Difficult to say conclusively from the PSA image.
A brief description of the two common ways for brake drums to be attached to cars.

The good old fashioned way is for there to be a hub with the wheel studs or threaded wheel bolt holes firmly attached with good old fashioned wheel bearings on to the axle. The brake drum is then passed over the wheel studs - or lined up with the bolt holes - fixed with one or two grub screws, then the roadwheel is bolted on and the brake drum is held firmly in place (being sandwiched between the hub and the roadwheel). Easy to service and no great dramas. See picture:

Drum brake, 'How A Car Works' - Fair use.

Much more common now there are the wheel bearing-in-drum type drum brakes. The roadwheel bolts / bolt holes are an integral part of the drum and the drum directly takes the load of the the roadwheel as opposed the hub in the above description. The bearing-in-drum type drum brakes basically take the place of the good old fashioned hub, and therefore they have their own version of a hub nut. Normally this would be a large nyloc nut. The issue with this type of brake drum is that you have to disturb the 'hub nut' to get at the brake shoes and/or brake mech.
If you look at the photo below, you can see the how the bearing would sit in the drum, then the drum would be attached to the stub with a nut.

Integral drum brake 'How A Car Works' - Fair use.

There are normally cautionary tales of the 'must replace the wheel bearing if you disturb it' nature. Some cars this will be essential, some you have to make a judgement call on. On a low mileage car (that I owned) where it wasn't mandatory to replace the wheel bearing, I'd favour not replacing it. You would, however, realistically need to replace a nyloc hub nut with a new one. You could reuse the old one if you really REALLY had to, but best practice is to repalce it.

To work out what type of brake drum you've got, you could have a ferret around on the PSA parts website to see if you can find a conventional type of rear wheel hub for your ION (as per top photo), or whether there's only pictures showing a hub stub (as per bottom photo).


Edit:
Rather surprisingly, my ageing copy of Docbackup lists the C-Zero, and providing there've been no major changes in the design of the rear brakes since my copy was created, it looks like your brakes are the good old fashioned wheel hub type

C-Zero rear hub PSA - fair use

Edit II: Cue - the sound of a penny dropping in my brain. Yours is a rare beast.... a modern day rear wheel drive car Hence it's got the good old fashioned type of rear hub

[Mandrake]

Edit:
Rather surprisingly, my ageing copy of Docbackup lists the C-Zero, and providing there've been no major changes in the design of the rear brakes since my copy was created, it looks like your brakes are the good old fashioned wheel hub type

C-Zero rear drum.jpg

Edit II: Cue - the sound of a penny dropping in my brain. Yours is a rare beast.... a modern day rear wheel drive car Hence it's got the good old fashioned type of rear hub

Maybe! Keep in mind this car doesn't use a conventional live rear axle.

It uses a Di-Dion rear suspension with a horizontal stabiliser bar, and has half shafts from the gearbox to hubs with triax and CV joints each end, just like the front of a front wheel drive car - so there must be a stub axle going through the middle of the drum with a stub axle nut. I very much hope the outer drum lifts off without touching the stub axle nut...!

I thought I'd taken a picture of the hub in the past but it looks like I was focusing on what was behind the hub - you can see it in the corner of these two pictures:

You can see the stub axle nut visible, but I'm presuming it's through a hole in the outer hub and doesn't prevent you lifting it off. Is it normally just the tightened wheel nuts that holds the outer drum in place or are there small screws like with discs ?

[Mandrake]

Just remembered I have an electronic copy of the service manual for the car!



Reading through the rear brake section it looks pretty straight forward...

[bobins]

Is it normally just the tightened wheel nuts that holds the outer drum in place or are there small screws like with discs ?

The parts list has No.16 'Drum Fix screw(s)' listed so it should have a couple of small grub screws holding each drum on.

Without wishing to do the 'grandmother/egg sucking' routine.... do remember to release the handbrake before you try to remove the drum !

[white exec]

If the small screws are countersunk, they not only hold the drum on (lightly) to prevent it dropping off when the wheel is removed, but they can (depending on model) also provide the proper location of the drum on the axle. The wheel studs often don't do this, as they pass through holes larger than the studs in the drum.

[RichardW]

Simon, I've sent you the PSA docs for the rear brakes - but I see you have another source . Amusingly the PSA docs say to remove the drum "remove wheel. Remove Drum" No mention of any screws, and I can't see any on the diagram, so it would appear to just 'lift' off. Might need some persuading over the studs if it's never been off. I wonder if you might find a debonded lining....

I dislike rear drum brakes nearly as much as I dislike exhausts! My worst effort was on our first ZX - failure of a wheel cylinder was caused by some nugget being there before me and making a bog of assembling it which had resulting in a shoe twisting till it let the piston pop out. This had ruined the cylinder, shoe and the drum. They had also made a bog of fitting the adjuster, and broken it. Removing the pipe from the cylinder resulted in its failure - and same on the other side. So this resulted in new drums, bearings (in the drums), shoes, adjusters, cylinders and pipes - and finding someone on Saturday morning to make the pipes and press the bearings in. To cap it all, said nugget had also managed to mash the thread on the (M20!!) axle thread, so I was luck to get the hub nut back on Here's hoping yours is more straightforward!!

[bobins]

Amusingly the PSA docs say to remove the drum "remove wheel. Remove Drum"

That made me chuckle when I saw it on Docbackup. They might as well say 'Fix the bits you want to fix'

No mention of any screws, and I can't see any on the diagram, so it would appear to just 'lift' off. Might need some persuading over the studs if it's never been off. I wonder if you might find a debonded lining....

The p/n is out of shot on Simon's picture extract, but the screws are number 16 as obliquely referenced in the screw shown in the box in the top left hand side.

[RichardW]

The p/n is out of shot on Simon's picture extract, but the screws are number 16 as obliquely referenced in the screw shown in the box in the top left hand side.

It is, but if you look carefully at the diagram you will see the screws 16 shown as going through the back plate holding it on, so the description is misleading...

[bobins]

....... so the description is misleading...

Situation normal then