My C8 munched through a set of rear pads in about 22K miles when I first got it and the handbrake never felt right. Cue a heated discussion at the dealers and they grudgingly agreed to replace the rear calipers. This escalated into a counter-thumping row when they billed me for the pads (which I lost).
Now the handbrake feels odd and the right self-adjuster isn't self-adjusting any more. A new caliper is little more than the service kit but do I replace both calipers?
New handbrake cables too as they are both sticky.
Even after half a lifetime messing around cars I don't recall replacing a caliper with 'normal' hydraulic fluid; all my history is with Citroen green fluid braking systems. I've got my flare spanners and a big hammer; any preference for releasing fluid? Heat or violence? any comments and advice most welcome.
TIA
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If I was in your position I'd have a good look (and maybe ask) on a Citroen forum or two.
See if you can find somebody else who has fallen down an unexpected hole, and what they have to say about it.
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Never had a problem with the rear brakes on our C8 which we sold this week after 9.5 years and 57,000 miles.
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Try on the flat with handbrake off and engine running pump the brake pedal and hold it for a few seconds it may auto adjust the rear brake then let the handbrake up while listening to the clicks this is the way to do it on some cars now.
Check your handbook for handbrake opperation.
This vectra from new the calipers on the rear are aluminium and corrode pushing the rubber sleeves of the caliper bolts to nip together causing it to stick and not slide, hence one set of brakes wear uneaven and don't auto adjust as it should.
You "may" have a similar problem.
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''A new caliper is little more than the service kit but do I replace both calipers?''
I'd have a good look at it, peel back the dust cover and if it looks reasonable and is working stuff some brake grease inside and leave it be.
''I've got my flare spanners and a big hammer; any preference for releasing fluid? Heat or violence?''
Plus Gas squirt for about a week before you commence would be helpful, also soak the other end of the brake pipe and the ends of the flexible (both sides) in case you end up chasing brake pipes till you get to one that will undo, hopefully not, you might need a bit of heat to undo the pipe where it enters the old caliper.
Taking the opportunity to bleed the whole system?, if so give all the bleed valves a squirt of PG at the same time.
Does it really need new cables or could you feed oil into them by disconnecting and working them gradually.
Brake grease for pistons then and sliders, and some coppaslip for other bits, and PG releasing fluid.
One other thing, assuming you work full time in the week and this is to be a weekend job, i'd try and dismantle the evening before so you have a chance to find any extra parts, or get new brake pipes made up as necessary, definately not a Sunday start if Lady H requires the car for Monday morn or you'll be in the doghouse if it goes wrong.
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Thanks for your observations, especially GB.
There is no dust cover; the handbrake lever goes straight into the caliper body. I'm assuming the self-adjuster is buried behind the piston and possibly immersed in brake fluid. Ebay item 151003805169 shows a pic.
Brakes are bled every year so the nipples are free. No danger of Mrs H wanting to drive the old bus unless some catastrophic emergency occurred.
Last edited by: hawkeye on Mon 29 Apr 13 at 14:33
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Dust cover i meant was the piston dust cover, prise that back gently and have a look see at the state of the piston and splash a bit of brake grease in there whilst about it if it looks reasonable.
Bled every year? you're worse than me, i'll be directing accusations of taking maintenance to extremes in your direction from now on H..:-)
Just realised i have no idea how the modern caliper incorporating handbrake works, stripped and refurbed enough of those old Girling swinging calipers as fitted to P6 and Zodiac 1V's in me time, they were a purely ratchet adjuster effort which invariably became corroded and stopped ratchetting as soon as the dust/water seal failed, within 2 years then on Zodiacs being beside the wheel, but lasted years on P6's being inboard beside the rear diff, mechanism dry from factory no contact with brake fuid unless leakage.
Anyone got a link to a cutaway or good description of the workings of the modern type of caliper as fitted to H's C8 or any of the other modern offerings.
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>> Anyone got a link to a cutaway or good description of the workings of the
>> modern type of caliper as fitted to H's C8 or any of the other modern
>> offerings.
Is this any good?
www.brake-caliper-painting.com/citroen_c8.html#.UX6nfKIsmSo
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Tried to answer that last night C, but the forum went to pot.
Couldn't see a cutaway or description of a mechanical cable handbrake brake caliper there, maybe i'm looking in the wrong place as usual.
I'd like to see what the automatic adjuster mechanism is like.
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>> I'd like to see what the automatic adjuster mechanism is like.
You're right, it's the wrong picture. I can't find one of the adjuster.
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>> Anyone got a link to a cutaway or good description of the workings of the
>> modern type of caliper as fitted to H's C8 or any of the other modern
>> offerings.
That got me thinking. Here's a description for Lexus (page 4): www.autoshop101.com/forms/brake06.pdf
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Thanks Tom, thats a very good description of the operation, well found.
quote ''The automatic adjusting mechanism maintains the operating clearance
between the pads and the rotor as the pads wear down with use. The
primary assembly which makes this possible is the Sleeve Nut and
Adjusting Bolt. The Sleeve Nut is held by the Clutch Spring which
allows it to turn in one direction only. The diameter of the Clutch
Spring is slightly smaller than the diameter of the sleeve nut and
allows it to turn in the unwind direction only. The clutch spring is held
stationary with one end attached to the piston.
When the brake pedal is depressed, hydraulic pressure forces the
piston to move to the left. The movement of the Piston exerts pressure
on the Thrust Plate and Thrust Bearing against the Sleeve Nut
causing it to be screwed out from the stationary Adjusting Bolt. The
Sleeve Nut can be easily screwed out because the Clutch Spring
unwinds and therefore does not prevent the Sleeve Nut from rotating.
The distance that the Sleeve Nut screws out from the Adjusting Bolt is
equal to the amount of pad wear.'' unquote
Simple and clever using the unwinding action of the clutch spring to let the thread unscrew taking up adjustment as necessary.
Not a particularly user serviceable item though, its a mechanism that would (IMO) benefit from a periodic strip out, clean up and lubricate, but i couldn't even tell you if overhaul kits are available for calipers any more.
'ere Hawkeye...'ows about dismantling that caliper you're going to replace and do us a write up and a few pics of whats caused failure?...bet i'm not the only one would like to see such.
As an aside, i once had the genuine Toyota makers workshop manual for my Landcruiser, what a fantastic easy to read well written journal that was, see the Lexus article is just as plainly written for the mechanic.
Last edited by: gordonbennet on Tue 30 Apr 13 at 20:44
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Thanks all for the comments.
OK I've had a longer look at the caliper. I've doused the union in penetrating oil and used the footbrake to push the piston out until the dust cover is nearly wrinkle-free. I've prised the dust cover open with a small knitting needle (no sharp edges) and filled the cavity with brake grease. Using the piston resetting tool the action is a lot smoother than when I reset it last time. I've pushed the piston out, greased behind the dust cover and reset it twice more. There's no sign of corrosion on the bits of the piston I can see. It's all put back together now but I haven't driven the car yet.
I don't fancy my chances of getting the union out of the caliper; my 11mm flare spanner is a loose fit already and it feels as if it's going to round off the first time I give it some. And yes the 10mm spanner is clearly too small. With my luck I'll need to chase the pipe all the way to the ABS block.
If the grease treatment doesn't work I'll get some new pads and see if the adjustment will work on a different part of the thread. It'll need new pads anyway whatever I do. Doing a write up on the dismantled caliper isn't a priority at the mo.
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Update.
Mis-diagnosis on my part. The o/s handbrake brake cable moved freely when disconnected from the caliper but was stiff when held in the position it would be if connected, if you follow ...
The self-adjuster has been freed off, new discs, pads and 2 of the 3 handbrake cables renewed. I've now got a handbrake that works equally on both wheels and the calipers fight another day.
Thanks again for all the input.
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Hi Hawkeye,
Did your C8 problem stay fixed ?
I ask because I've got a very similar problem on my C8. Both hand brake levers return on their own when disconnected but, with the cables connected, the right hand brake was sticking. It seemed as if there was stiction in the cable.
I replaced the cables yet it is still the same.
When I release the hand brake, the left hand lever frees off OK but not the right hand one. It seems that the 'balancer' in the centre of the car needs just a little bit of assistance to move to the right and free off the right brake.
Not sure this makes much sense but if you have any thoughts or advice it would be gratefully received !
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Citroen C8 MPV - Rear calipers - wish me luck! - AnotherJohnH
