Xantia rear caliper question

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MikeT
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Post by MikeT »

I hope you plusgassed those heatshield bolts! Also wire brush any extruded ends of the bolts as they may have "grown" since being fitted and they shear like butter after a few turns. When Toby seperated his rear caliper I didn't see any seals pop off or require renewing and they went back together ok. It's not necessary to split them anyway, is it?
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Post by citroenxm »

The rear caliper seal is recessed into the caliper on both halfs, and stay put when the caliper splits IF THE CALIPER FEELS THOUGH ITS NOT GONNA SPLIT DONT FORCE IT you maight get away with leaving it as one!!!

The Two seals Butt up together when you put the two halfs together..

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Post by Xaccers »

The caliper can be moved enough while attached to the pipe to swap the disc, just be gentle with it.
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Post by citronut »

it dose not hurt to split the calliper's, and you dont usualy need to fit the one seal not two as Paul said between the calliper half's, you can fit a new one if it gives you peace of mind, u usualy remove the pad retainning bolt first then the two 17mm bolts which hold the calliper to the arm, and yes you can leave the other half dangling on its pipe if you are carefull,

by splitting the calliper it allows you to get in to clean the surfaces up the pads run on, and the only thing which might drop out is a small metal tube which is somtimes in the fluid through port between calliper halfs,

heat shield ??? you mean dust shield as there is no heat shield on the rear brakes, and even if these fixing bolt do shear off and you dont salvage the threads, you can drill the holes out and just fit nuts and bolts

regards malcolm
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Post by citroenxm »

citronut wrote:it dose not hurt to split the calliper's, and you dont usualy need to fit the one seal not two as Paul said between the calliper half's, you
It was late, and I couldn't remember if there was a seal on both halfs or just one side.. Cheers Malc, ill keep it in mind, I dont often split a rear caliper.. :D

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Post by MikeT »

My memory's like a collinder, here's the link giving the sizes required. http://www.frenchcarforum.co.uk/forum/v ... ht=#179882
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Post by MikeT »

I tapped from the inboard side where space was a little restrictive to ensure a perfectly perpendicular angle of attack but once the tap bit, it was more a matter of chasing the original thread than actually cutting a new one. The remnants of stud that wasn't drilled out just pushed out the other side.

If you try the easiest to access first, the others will be a breeze. Operation is simple - Half a turn in, quarter turn out, repeat like that.
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Post by citronut »

i would try (loads of PERCY WHAT SIT) boltting the complete calliper back to the arm with the disc left off, then start the engine have a tray under the calliper and both pads just laying in place, now press with gradualy more presure till with a bit of luck the piston move/pops out,

dont grip the piston side walls with anything as you will damage it,

if that dose not work try squeezing the piston back in with the likes of a G clamp, or if you have a small vice stan it on some blocks under that half of the calliper and try to wind it in with that,

once its gone in use the braking system to get it back out, do this two or three times till it goes back easy

regards malcolm
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Post by AndersDK »

Hi Mike -

Use a carpenters clamp to prevent the working piston popping out, then simply hold the brake pedal down until the seized piston pops out against the clamp.
Now polish the exposed piston surface and grease it with LHM (or standard brakes service grease - that white, red or blue stuff in small bags), push it in as far as it goes and repeat the process.
Repeat for all pistons until you are happy with their operation, only be careful to restrict how far they can pop out ...
... unless you want them out in your hands to clean them really well.
(will cause a bit of greasy mess and a few mL LHM, but nothing serious)

Remember that the rear suspension MUST carry the weight of the car to get a feed pressure for the rear brakes. Otherwise nothing happens when you press the brake pedal ...
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Post by myglaren »

The hydraulic system on the car is the best tool to push the piston out. Do as Malcolm says but have some sort of shim to prevent the piston coming right out of the bore (unless you want it out completely of course, along with some LHM so have a bucket in place to catch it)

Note that the rear brakes won't work with the rear suspension arm dropped completely, you need to raise it. The more it is raised the better the brakes will work (more pressure on the suspension).

I discovered this accidentaly after replacing rear discs and calipers along with some piping.

Couldn't bleed the brakes and for some reason lifted the rear suspension arm with the engine running.

It responded by moving back down, as it should but took me by surprise and I almost lost an arm to it, close thing. First time I had worked on an hydraulic Citroen and wasn't aware of the dangers.

I reckon that although it is more of a clart on it would be best to reasemble the whole thing but leave the pad out of the stuck piston half of the caliper but have a shim in place, or a wide flat tool to enable you to force it back into the bore away from the disc once it has been ejected. Have the car on the ground with a fair bit of weight in the boot to give you plenty of pressure.
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Post by AndersDK »

To be safe - then have one side resting on its roadwheel, preferably lifted on to a wooden block to gain better work access.
The side you work on is then supported by an axle stand on the jacking point.

Have the car in normal height, to allow for a little height drop on the roadwheel side.
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Post by myglaren »

Actually, it may work with the suspension on full height. Can't try it as I haven't a 'proper' Citroen anymore :cry:
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Post by citronut »

the piston should go in all the way (balls an all TEA HE) so it is flush with the calliper face, i would get it to a vice one way or another the squeeze it all the way home, then as it will have now moved conect it back up to some hydraulic presure to pump it back out, you might find it will need the car fully up on its highest setting to allow full presure to the rear brakes,

once it has moved in and out repeat this several times, then if the piston will come right out just clean the side wall and the calliper boar,

DO NOT USE AN ABRASIVE ON PISTON OR CALLIPER BOAR,

then just slap loads of LHM in the calliper and on the piston and press them back together nice and square,

citroen calliper pistons used to have a thick coatting of teflon

you will probably find it was the pad that got stuck first were it had been fitted without any copper slip

regards malcolm
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Post by AndersDK »

One last comment :

Unless you have the bleed nipple freed up, dont let the pistons come out completely, because you will get air into the caliper cylinders that then needs to be bled out afterwards.
And those bleed nipples are a nightmare themselves, if they are stuck - OR if you snap them off ...

Otherwise you are on track, and just needs to get the pistons moving and lubed ...
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Post by citronut »

i agree with Anders
it will make it easyer to try and free your kniples off, if you fit the two calliper retainning bolts trough the one half of the calliper first,

also if you try to undo the pipe nut with an 8mm split ring sppaner and it feels like its going to round your nuts off, stop and try a good set of mole grips, the only down side to this if the nut dose free off is you will need to do it back up with the mole grip, as it will distor the hex of the nut making it so you wont get a sppaner to fit

regards malcolm
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