Xantia rear brake caliper bolts-removal

NewcastleFalcon · Post by **NewcastleFalcon** » 04 Mar 2010, 17:54

When my MOT comes up at this time of year I often wish I had stuck to my policy of ensuring a summer MOT date. The all consuming obsession of getting that pink failure sheet to turn into a green pass certificate is never helped with the prospect of working outside in sleet and snow.

Just for amusement over the coming days I will be turning my attention to:-

1 Sorting out the "light output severely reduced" from both nearside and offside headlights.
2 Offside front parking brake-cable fouling, and "recording little or no effort"
3 Rear brake discs excessively worn/ rear brake application uneven

The headlight bit is sortable-as is the parking brake stuff but the job which is filling me with the most dread is the rear brake problem.

Probably fairly straightforward if the bolts holding the calipers together didnt shear off, but thats exactly what's happened. I reckon I need to sort this out with the minimum of additional dismantling ie not having to remove the rear trailing arms and take them somewhere to get the remaining stubs of the bolts drilled out.

What in situ methods should I try first? Will your ordinary black and decker with the right sized drill actually get anywhere near drilling out a sheared off bolt if you cut the bolt off as flush as you can?

If a stub remains and if I can find a friendly welder, is the best method welding on a nut to the stub?, or more straightforwardly grabbing the stub with molegrips and roasting the "hole" red hot or a combination of the two?

If there is anyone who has conquered this problem I would like to learn from your experience

Thanks Neil

Post by **CitroJim** » 04 Mar 2010, 21:36

Neil,

Touch-wood I've not had any particular problems with the rear caliper bolts so I cannot comment on methods of stub removal should the worst happen.

My method to remove the bolts is to initially thoroughly wire-brush the exposed ends of the threads at the backs of the trailing arms and then douse in Plus-Gas and leave for a bit.

Then use a long breaker bar on the bolts. I use a metre-long bar and apply very gentle pressure to it. Like this I can feel the bolt beginning to twist; the bolts have some elasticity in them and snap when it is exceeded so go carefully.

I hold the gentle pressure on the bolt and if I feel a twist beginning I stop and let the bolt untwist itself whilst maintaining pressure. Basically, you set up an angular force in the bolt itself and the force of it's natural desire to get back to normal is enough to start it undoing. Sometimes this approach does not work and in such instances it helps to try tightening eh bolt before trying to undo it. Likewise, if you start a bolt and it goes tight on the way out, do it up a few degrees and then try undoing it again.

Hope that helps and good luck with the work. Don't forget to clean up the caliper where it joins to the trailing arm and apply plenty of copper grease to this joint to prevent electrolytic corrosion.

NewcastleFalcon · Post by **NewcastleFalcon** » 04 Mar 2010, 21:58

Jim
I will definitely try your careful method on the bolts I have yet to shear off. Unfortunately at least one definitely has sheared but I need to get the other bolt out (hopefully successfully using your method) before I know how much broken bolt is left poking out. If it proves to be enough to get a decent grip on it, your method may still work.
Is "plus-gas" better than or virtually the same thing as WD40? Is diesel a useful lubricant to soak through to the rusted threads as well?

Thanks Neil

Post by **RichardW** » 04 Mar 2010, 21:58

I've not actually done it, but.... The bolts are high tensile, so they'll be HARD! You will struggle to drill them with an HSS bit, but you might mange it with patience (slow speed!) and lubricant. You could always drill oversize and fit a through bolt with a nut on the back. If you can get hold of some cobalt tipped bits you'll stand more of a chance. Probably better if you can find / borrow a MIG - find a nut with a thread a bit smaller than the bolt, hold it (with a tool, it soon gets hot!) over the stub, and fill the centre with weld. Going steady with a spanner on the nut, and some plus gas on the thread, and you might get it out. The heat from the MIG will help free it. If you could find someone with an Oxy-Acetylene torch, heating it up till it glows might be enough to free it - you have taken the load off by snapping it, so if you free it, you might just be able to unscrew it by hand.

Is it an estate - these use longer bolts than hatches, and seem more prone to breaking. I had a go at mine, but the first one was being reluctant, so i gave up. Just staving the pain off for another day I guess....

Stempy · Post by **Stempy** » 04 Mar 2010, 22:01

Not sure that copper grease is the best thing for an alloy/steel interface, better to make up a gasket.

The bolts are 9mm, if you manage to drill them out you could probably re-tap the holes to M10, or, if you really bugger it up and can't tap M10 get some slightly longer bolts and use nuts placed behind the mounting plate.

If you do manage to get them out ok then be sure to use a thread lock compound on reassembly as this will prevent them corroding in again.

xmexclusive · Post by **xmexclusive** » 04 Mar 2010, 22:06

It may be worth also supporting the caliper from underneath so the load from the bar is only trying to rotate the bolt not pull it downwards as well.
The weakest point in a high tensile bolt is the inner end of the thread. As the thread cutting tool ends its cut it typically leaves micro cracks in the bottom of the v cut. Putting any significant bending on the bolt at this point can cause the threaded portion to snap off.

John

NewcastleFalcon · Post by **NewcastleFalcon** » 04 Mar 2010, 22:21

Thanks for your contributions. I have already optimistically reserved 4 new bolts at the Citroen Dealers in town (99.9% sure I said I had a hatchback), anticipating at some stage reassembling the rear brake calipers and finishing the job. Canny bit water to go under the Tyne Bridge before that happens I suspect.

Neil

Post by **RichardW** » 04 Mar 2010, 22:26

Plus Gas is orders of magnitude better as a release agent than WD-40!

DaveW · Post by **DaveW** » 07 Mar 2010, 13:03

I had the same problem but in my case it was the build up of oxide between the caliper and the suspension arm which had, apparently. caused the bolt to fail !!!!. The build up was massive and the pads resembled wedges (I had just bought the car and was doing a few checks when I discovered the problem).
However, I did the usual precautionary cleaning of the threads as suggested by RichardW, applied a squirt of White Spirit followed by a couple of spots of 3-in-1 (my favourite combination as release agent) and was able to easily remove the stub with vice grips.
I know it sounds odd but I have found that often it pays to apply a slight positive pressure to a seized bolt or nut that is reluctant to shift - i.e. clock wise movement - before re-attempting to undo it anti-clockwise.
It can also help to give the stub of a broken bolt a few taps, with a punch and directly in line with its axis, to loosen any rust - but don't be too heavy handed.

Dave.

citroenxm · Post by **citroenxm** » 07 Mar 2010, 20:17

Ah ha! Some one HAS hit the nail on the head!

It has absolutly nothing to do with the bolts siezing in the arm what so ever, and it is the corrosion between the caliper and the arm..

What happens is it builds up behind the caliper, then while this is happening, it pushes the caliper at an angle outwards, useually inner (nearest the centre) end first, this then bends the bolts and causes the Siezure you get.

They ARE drill-able, however all is not lost if you ruin the thread as you can get a longer bolt and nut, and have the bolts go right through to the other side of the arm and put the nut on the other end..

Stopping the corosion? A grease covering between the caliper and arm, or copper grease, or a gasket.. I think if the two flat surfaces which have a rather good tight fit originally can corrode there may not be much in the way of stopping it, but controlable by regular checks..

As said, the other clue if you cannot visually see it, is the Wedge Wear on the pads.. due to the angle of the caliper.

CHECK YOURS NOW! You may be surprised to find it in a similar condition!

Paul

DaveW · Post by **DaveW** » 07 Mar 2010, 21:41

Just so , Paul.

This was on the 1.9TD. I must check out the recently acquired 1.8i soon as that is about ten years old so there must be some corrosion lurking behind the calipers on that.

What annoyed me was that the previous owner had the brakes serviced by a garage about twelve months before. This corrosion and build up of oxide doesn't happen suddenly so the mechanic(?) must have seen that the old pads had worn into a wedge shape yet he just went ahead and slapped on some new ones without bothering to investigate the cause.

Incidentally, the best way of removing the oxide layer I found was to first chip off the worst and then to use an old worn hacksaw blade, at an angle, to gently 'saw' off the thin layer that remained before giving both surfaces a polish with emery cloth.
I thought about using Copper-ease but wondered if adding another metal to the mix might add to the electrolytic problem so in the end I just lathered the joint surfaces with HM grease.
That was over four years ago and so far all still looks OK.

Dave.

Post by **RichardW** » 08 Mar 2010, 08:56

I agree with Paul that it is the bending of the bolts that probably causes them to snap - undoing them progressively in synch should help to minimise this. I did muse in a previous thread that it might be better (especially on estates) to just grind the heads off the bolts, then pull the caliper and disc off the studs together, this would then give you plenty of stud to go at with Stilsons or similar. Of course you need the disc to come free of the hub, and there's some debate as to whether the caliper would pull free of the studs together - and this could leave you in a worse state than snapping the bolts off flush with the arm...!

But...having thought a bit more, you could grind the heads off, then remove the pad bolt, and this would allow the removal of the front half of the caliper, thus revealing a good portion of bolt to get the stilsons on with the tension removed, and avoiding the problem of having to remove the disc. Of course, you need to have the bleed nipple free so you can bleed to brakes afterwards.... no easy wins here

That'll be why mine is still running with the calipers touching the disc then!

DaveW · Post by **DaveW** » 08 Mar 2010, 12:32

.

Oops ..

I see that I incorrectly attributed the technique of wire brushing the exposed bolt threads and applying release agent etc. to RichardW when in actual fact it was CitroJim who wrote about that. ......

Sorry Jim ..................... it's an age thing you know.

Now what did I come into this room for ........................ ?????

Dave.

andmcit · Post by **andmcit** » 08 Mar 2010, 13:13

I've got this stinker of a job waiting for me on an Activa and as yet haven't
snapped anything yet.

I believe I can get movement on two of the four bolts of both callipers but
that doesn't just mean to say the bolts are stretching or twisting. So, following
the previous posts, the best attack now judging by the acute wedge of the
previous pads is to accept the inevitable shear of the bolts and cut the heads
off the calliper bolts? My problem is I don't have power near the car and once
I drive it near power I'll have disabled the car...

Andrew

Post by **CitroJim** » 08 Mar 2010, 14:09

If you can feel some movement in the bolts, work them back and forth gently to break the grip the oxide has on them.

Chances are, if you do this with care and follow the mantra of wire brushing the thread ends well and using Plus-Gas, you'll have a good, successful outcome...