Parking Brake Mechanisms - Stripdown and Overhaul

In the build up to dropping the engine in, I've been doing a few small last minute jobs. In some cases these are things I forgot I would have to do!

 

Parking brake unit refitted

I was so 'in the zone' that I didn't really take any photos of this job. There's not much to it but some photos might have helped to demystify things. I've had to use photos from all over the place. Dago Langen has been particularly kind in letting me use the photos that he took. I'm glad one of us remembered!

 

For some reason, replacement of the calipers wasn't included in the '814' repair manual. But if you are lucky, it might have been added to your PDF version of manual 814. If so, it will be at section 1 in volume 2 and shown as Operation DX.454-1. If it's not there, it can be found at Operation DX.454-1 in manual 518.

 

Even when you find it, you will see it just that - replacement of the calipers. Off and back on. It doesn't go any deeper than that. For example on changing the pads and fitting the anti-rattle springs.There aren't many parts, but it can be confusing trying to put them all back together.

Exploding diagram of the parking brake mechanism

On each side of the car, a pair of log arms (part 4) pivots on a shaft that is part of the caliper body. The brake pads (3) are fitted to the top half of the arms and when the cable pulls the arms together, it pulls the pads on to the disc. Strong springs (5) fitted to the cable push the arms apart again once the brake is released.

The cable pulls the arms together (photo: Dago Langen)

There is a bolt and lock nut through each arm to adjust the brake pads (not numbered in the diagram). These are VERY difficult to access when the engine is in the car.

The adjusters are awkward to access from any angle - even under the car

To hold the pads steady on the arms, each pad has a slot at one end that locates onto part of the main caliper body. That's really just to stabilse the arm and so the pad and arm pivot slightly. The pad needs to be able to move without it's slot binding or catching. To stop each pad rattling as you drive along, 'anti-rattle springs' (3) are fitted in the slots.

 

It's not an issue for me as my car is a 'proper' left hand drive car, but the 1968 parts catalogue shows that for a right hand drive car, there are a combination of three differnt lever arms used: a pair and two that must be handed......Other catalogues show different combinations of parts. The bottom line is that, if you have a RHD car, be careful you don't muddle your lever arms!

The part numbers show that, for RHD cars, the lever arm parts are 'handed'

The calipers of my car had been removed, dismanted, cleaned and primed when? 2015? Probably! Mine weren't quite as mucky as these, but you can see how the road muck can easily stop the brake mechanisms working as intended.

Parking brake unit removed (photo: Dago Langen)

It's hard to see, but there is a split pin on the end of each shaft. When those are taken out, the arms can be removed. And with the arms out of the way, the brake pads can be removed. You might find that small 'anti-rattle spings' also fall out.

Parking brake 'anti-rattle' springs

All the parts were degreased and any rust was removed. I paid particular attention to the shafts that the arms pivot on. as well as the bosses that the slots of the pads fit over. I bulk-sprayed some parts it included parking brake parts, even though I didn't assemble them at the time.

 

I cleaned up the threads of the adjuster bolts. These bolts are fairly specialised in that the hex head is very shallow. I suppose that if you needed such a bolt, you could grind down the head of a standard bolt.

The pads are the first things to be fitted. The pads I'd removed from mine back then were hardly worn but I was worried about them having oil or LHM on the surfaces. By chance someone was selling an unwanted new set at the D rally in June this year and so I bought those. I think that was probably the nudge I needed to remind me I still needed to do this job.

I chose not to re-se these pads but have hung on to them

I put a little copper grease on the bosses that the pads slot on to, just so the pads moved more easily. This partly to allow for ajustment and partly to compensate for wear - though there isn't really any of that. I winkled the anti-rattle springs back in the gap in the slot. 

Note the anti-rattle spring in the slot (photo: Dago Langen)

The factory says there are FOUR anti-rattle springs to a car - that's just one per pad. Because of the way they fit, it feels odd to only attach a spring to one side of a pad and it's tempting to think that each would have two (one either side of the mount) but that is not what Citroen intended, and you will struggle to fit more than one spring per pad in the slot.

I attached the adjuster bolts to the arms. I put a little grease on the threads to make them easier to adjust in due course. I wound the bolts on as far they would go at this stage and only loosely fitted their lock nuts.

Adjuster bolts (photo: Dago Langen)

The arms were fitted on their shafts. It's important that the lever arms can pivot freely. I found that with my enthusisatic painting, they were sticking on the pivots, so the pivots and the holes through the arms got a rub down with emery cloth. The parts books show that the levers have a bush going through them (part 7 in the diagram above), but I didn't notice them on my parts. Perhaps they are pressed in? Happy that the arms moved freely, and that the pads could slide on their bosses, I fitted the split pins to secure the arms in place.

 

Before fitting the calipers to the bellhousing, I used carb cleaner to clean the pad surfaces, and the disc brakes. I offered up the calipers, slipping them over the disk brakes, and put the securing bolts on just hand tight at this stage. 

 

While I had the opportunity, I adjusted the pads with the adjuster bolts so that they just contacted the disc brake. The manual says there should be a 0.1 mm gap between the disc and pad. I tried that but bcause of 'run out' on the discs ('warp' if you will) a 0.1mm clearance at one point left the pad rubbing when the disc was rotated. So I adjsuted my pads so that, when the disc was rotated, the pads *just'* cleared the disc in all places. I didn't tighten the locking nuts just yet.

 

The manual says that the order of jobs should be:

- Loosely fit the calipers

- Fit the parking brake cable and springs

- Tighten the calipers

- Adjust the pads

- Check the cable adjustment.

 

The only problem was that my engine was out of the car - so I couldn't fit the cable just yet so needed to skip that. You don't want the caliper bodies to rub on the rims of the discs. The workshop manual says that there should be a gap of 4mm between the edge of the disc rim  and the arch of the caliper body. 

Caliper assembly fitted (photo: Dago Langen)

I followed Dago's lead: the easiest way to set the gap is to gently wedge a screwdriver in between the disc edge and the brake unit......

Make sure there is a gap before tightening the caliper units (photo: Dago Langen)

.....while tightening the brake unit bolts. The bolts needed to be tightened to a torque of between 10 and 11m.kg.

Tightening the brake units (photo: Dago Langen)

Once the caliper units were in place I re-checked the adjustment of the pads. When setting the adjustment, the manual says that the caliper arms should be pulled together. I checked and made a couple of adjustments. Maybe I was fussing, maybe the calipers had settled in a different spot. I checked that everything moved as intended and that was that for the moment.

I won't be able to refit the operating cable and springs until the engine goes  back into the car - that's happening tomorrow!