C5 Mk1 DIY rear calipers fix

[daniel_st]

Hello!

As my first post, I wanted to show you a little fix I did for the case of falling apart rear brake calipers on the C5.
One of the known issues for these calipers is that the hole through which goes the bolt that holds the pads in place, is too weak and falls apart with time.
Then, technically nothing holds the brake pads to the caliper, and if subjected to enough force, they could move out of place/fall off.

I drilled two small holes in the wall of the external half of the caliper (careful not to hurt the body, as it's hollow and full of brake fluid!) and used the stock tension bracket to apply tension to the center of the bolt itself and hold it in place.

Of course the better option is to buy new calipers, but if the pistons are ok and the caliper isn't leaking, and its only issue is that the "ears" for the pads bolt broke off, this is a solid fix.
I did put the nut and plate over afterwards, everything assembles as normal. The bracket easily moves out of the way when you need to change the pads.

Check out the attached pics

Hope that helps someone! Cheers!

[PaulC5]

I have found using a bit of copper grease on the holes in the caliper and on the pad retaining bolt prevents the corrosion that lets the caliper hole lug break off. Also the bolt should not be over tightened since the caliper alloy is not strong and the lugs could break off.

On our C5, every couple of years I remove the rear calipers to apply copper grease to the suspension arm/caliper where they contact to prevent the galvanic corrosion that can occur due to dissimilar metals which if left can push out the calipers and touch the wheels. However, when removing the caliper it is important the pad retaining bolt is in place or the caliper can split and leak brake fluid as the caliper retaining bolts are slackened.

[aspire_helen]

I doubt it would pass a UK MOT! As with Paul, due to annual MOTs, I inspect the rear callipers at least annually.
I once bought a second hand suspension arm with calliper fitted - the corroded holes had been repaired with the brass plate rivetted on.
Adding to Paul's comment.... Daniel, do your discs still run flush with the calliper face, or does it appear that one edge of a calliper is getting close to the disc. If so, it may be the calliper has been pushed away from the suspension arm due to aluminium corrosion expansion between the two. That will put an incredible static strain on the calliper bolts. I know, because one day while breaking on a motorway slip road there was an almighty clunk from the rear. One of the bolts had sheared. It was only when I removed the calliper that I realised the corrosion and a slight twist of the calliper. The bolt had been progressively pre-loaded by the twisting calliper until the point when it was waiting for hard braking to give way.
Be aware there is "advice" on how to avoid the corrosion online and YouTube which is potentially DANGEROUS.
(1) It is suggested that if a calliper starts rubbing on the disc (due to the afore mentioned corrosion distortion), simply grind away that bit of the calliper. No. Remove the calliper, clean and seal the jointing faces and fit NEW bolts.
(2) It is suggested to use stainless steel bolts. No. The original bolts are Grade10 steel, much stronger than standard 8.8 because they are very long and subject to virtually pure shear loading. Always use Grade10 steel bolts.
(3) It is suggested copper greasing the bolt shafts inside the calliper. No. Citroen (as reflected by Haynes) requires the calliper through holes to be filled with a suitable hard sealant (injected via the holes provided for that exact purpose). This is not a corrosion prevention measure. It is intended to firmly secure the bolts in the callipers to provide a more rigid (and hence stronger) assembly. The specified tightening torque assumes that the bolts are held rigid within the through holes as if they were part of the calliper itself. Its not the best design.

Splitting the calliper is not a problem provided the tiny oring between them is recovered. Having said that, I always use finger clamps to keep the 2 halves together when unbolting the main bolts.

Finally, rear callipers are usually sold "handed". In fact, the 2 halves may be identical and can be swapped left and right. All it requires is the bleed valve and brake pressure lines to be swapped over - their tapped holes are identical..

[Hell Razor5543]

On my first C5 I had to get work done on the rear brakes. I supplied gasket paper and they put some between the callipers and trailing arms. Unfortunately I did not get to see if this prevented the corrosion, as about a year later I was rear shunted and she was written off.

[daniel_st]

Thank you all for the replies, I am aware of the corrosion issue - mine are *relatively* clean and have not twisted visibly. I'll look into corrosion prevention when I replace the calipers themselves. That the two halves are identical is of MASSIVE help, thank you so much for letting me know!! That means I can buy only 1 new caliper and reuse the best halves of my calipers as outer.
But anyway, here I just wanted to show a quck and dirty fix for already destroyed bolt holes.
And I'm not in the UK, and it passes MOT in Bulgaria just fine, as the brake pistons and hydraulics are not affected and function as designed
Thank you much, fellas!

[aspire_helen]

Ref identical halves. I meant that you can re-configure a left hand calliper to fit on the right, and vice versa. Swapping halves of callipers from different manufacturers may not work; it would rely upon the brake fluid channel between the two halves aligning, and the oring sealing. But worth a try perhaps.