Rear Brakes

[Guest gs fan]

I'm really glad I joined this forum , for usefull info' it's way better than the dealers or a Haynes manual ( which of course isn't available )

I read Coastline taxi's tip on removing the rear caliper with interest and looked in "Search" for more on this subject as i've been baffled by why the N/S rear caliper on my C5 has a habit of overheating slightly , and also when I replaced the rear pads last year the inner pads would not go in , a freindly indy' garage managed to get the inner ones in but did not shed any light on what was the problem .

In the search info i found the answer , that corrosion was moving the caliper out of alignment .

I've investigated today and yes all the symtoms are there , the pads are wearing in the wedge shape described by the many contributers and the caliper is much nearer the disc at the inside.

Now , I also read that many of you say that this is not a job for a lad armed with no more than a socket with a big leaver attached as the bolts are very hard to remove , I,ve found the holes that Coastline described and I've filled them with the WD40 , this I thought would assist whoever has to remove them.

If I got a garage to remove the caliper does cleaning the mating surfaces and renewing the bolts cure the problem , or is a new caliper required?

Is it worth trying to slacken the problem bolts and do the job myself ?

Thanks to all for the great information posted .

[myglaren]

When I had mine done I was warned that sometimes removing the calipers destroys them if the corrosion is really bad and they always like to do it early in the day and be assured that a replacement set of calipers is available just in case.

 

As it turned out mine came off reasonably easily and were cleaned up, replaced and new pads fitted.

 

A few people have done it themselves, notably Mr. Coastline who has a fair bit of experience with car repairs. May be a bit much for a first-time project.

[Johndouglas]

If I got a garage to remove the caliper does cleaning the mating surfaces and renewing the bolts cure the problem , or is a new caliper required?

 

I haven't needed to do my C5 calipers, but on my previous Xantia the pads went wedged shaped. I got the calipers off and cleaned off the corrosion which was surprisingly hard and difficult to shift. There was no problem in refitting them.

[Guest gs fan]

When I had mine done I was warned that sometimes removing the calipers destroys them if the corrosion is really bad and they always like to do it early in the day and be assured that a replacement set of calipers is available just in case.

 

As it turned out mine came off reasonably easily and were cleaned up, replaced and new pads fitted.

 

A few people have done it themselves, notably Mr. Coastline who has a fair bit of experience with car repairs. May be a bit much for a first-time project.

I think you may be right , I know a local indy' garage that will tackle the job .

Thanks as ever for the advice...

[Guest gs fan]

I haven't needed to do my C5 calipers, but on my previous Xantia the pads went wedged shaped. I got the calipers off and cleaned off the corrosion which was surprisingly hard and difficult to shift. There was no problem in refitting them.

Maybe a bit risky to attempt myself , most of the contributers say that although the Xantia problem is the same the calipers come off easier , the C5 is very difficult in this area apparently.

Thanks for the advice...

[coastline taxis]

Maybe a bit risky to attempt myself , most of the contributers say that although the Xantia problem is the same the calipers come off easier , the C5 is very difficult in this area apparently.

Thanks for the advice...

To be honest weve never took the bolt fully out yet we always just give them four or five turns and the caliper just comes away(after having removed the pads and take the 2 grub screws out of the disc). We then move caliper to one side and sand down with the drill. Now dont ask me why but everyone that weve put back together has went straight away by locating the bottom bolt in first we tried the top bolt first and its awkward and dosnt mary up so put bottom one in first

[Guest gs fan]

To be honest weve never took the bolt fully out yet we always just give them four or five turns and the caliper just comes away(after having removed the pads and take the 2 grub screws out of the disc). We then move caliper to one side and sand down with the drill. Now dont ask me why but everyone that weve put back together has went straight away by locating the bottom bolt in first we tried the top bolt first and its awkward and dosnt mary up so put bottom one in first

Thanks for that Coastline , I'm just treating it with WD 40 in the hope that the day I decide to try the bolts it will help in their removal , would heating up the area where the bolts go in help . or will this damage the caliper ? also if I do manage to get it off and cleaned up should I treat the area with anti rust treatment ?

[coastline taxis]

Thanks for that Coastline , I'm just treating it with WD 40 in the hope that the day I decide to try the bolts it will help in their removal , would heating up the area where the bolts go in help . or will this damage the caliper ? also if I do manage to get it off and cleaned up should I treat the area with anti rust treatment ?

Hi gs

We have heated them in the past and had no problem at all in doing so. Obviosly pointing the torch away from the caliper and we normally put copper slip on. However since reading the advice on this forum we have been making gasket out of heavy duty black bags and using that instead of the copper slip. Also just squrting wd into the holes will have very little effect as it wont affect the locktite squirt brake cleaner/thinners/easy start in every 20 mins for a hour then the wd. If you havent got heat the turn the bolt out half a turn squirt it with wd then tighten it and just keep working the bolt back and forth with plenty of wd and it will come out.

[Guest gs fan]

Hi gs

We have heated them in the past and had no problem at all in doing so. Obviosly pointing the torch away from the caliper and we normally put copper slip on. However since reading the advice on this forum we have been making gasket out of heavy duty black bags and using that instead of the copper slip. Also just squrting wd into the holes will have very little effect as it wont affect the locktite squirt brake cleaner/thinners/easy start in every 20 mins for a hour then the wd. If you havent got heat the turn the bolt out half a turn squirt it with wd then tighten it and just keep working the bolt back and forth with plenty of wd and it will come out.

Thanks for additional advice . I will tackle the job soon....the N/S caliper has moved but is not as bad as some when I read the many tales of woe re' this problem on this forum . I suppose this is the time to correct it before it does damage.

I asked the dealer out of interest if they were aware of this issue but they played ignorant on the subject . Reading all the info' here from many owners and most say this fault goes way back to the BX layout I don't believe that they havn't come across it . You would have thought that Citoen would have re-engineered the suspension arm / caliper long before now eh !

Great cars with equally great flaws...

[Guest gs fan]

This would be a good post to pin at the top. It contains the important points to do the job which I have put together below:

 

- raise car suspension to its highest level, jack up the car, use axle stands, remove wheel,

- use brake cleaner/WD40 in the holes in the caliper to help free the bolts,

- remove the brake pad cover bolt/ cover/ brake pads (knock out from below if seized in place) but then refit the bolt which held them in place so the caliper does not split,

- undo the caliper bolts enough so the caliper is free,

- slacken the disc holding screws (I did not have to do this),

- move the caliper out (no need to disconnect the brake fluid pipe),

- clean the corrosion from the back of the caliper and suspension arm using file/drill/emery paper,

- use a gasket made from heavy duty black plastic bag (or copper slip grease) to prevent galvanic corrosion due to contact of the different metals of the alloy caliper and steel suspension arm,

- refit the bottom caliper bolt first since the top one does not line up (interesting since the bolt I cross threaded and snapped was a top one), torque setting 70 Nm,

- refit the old brake pads (or new ones if not worn evenly) after cleaning their contact parts in the caliper, use a bit of copper grease down the pad backing plate sides and back to avoid seizing/squealing ,

- refit disc screws (10 Nm) if slackened and wheel (90 Nm).

 

To remove the loctite from the caliper bolt holes a long 10mm drill could be used but this will require removal of the bolts (do one at a time and refit whilst the other is done) and be carefull not to touch and damage the threaded part in the suspension arm. Officially I think you should inject fresh loctite down the length of the bolts through the holes in the caliper when refitting, I suspect to prevent corrosion between the bolts and suspension arm and if so then copper grease would do, but as a minimum loctite should be used at the bolt end in the suspension arm so they do not become loose.

Thanks for that , this seems to confirm all advice and put it clearly into one step-by -step article.

I've printed it off for future reference ...

PS. You should post a copy to Citroen UK for distribution to their Dealer network ...

[coastline taxis]

Thanks for that , this seems to confirm all advice and put it clearly into one step-by -step article.

I've printed it off for future reference ...

PS. You should post a copy to Citroen UK for distribution to their Dealer network ...

Hi totally agree with pinning the above and found the p.s bit very funny. Having spoke to the workshop supervisor at my local dealers and they are as just as sick with citroen as we are. Funny thing though is that the c5s i own dont seem to get as many faults as what is posted on this forum. Now while i would like to put it down to our brilliant mechanical skills i cant help wondering if its because these cars where designed to run and not little stop starts all the time. mine are on the road from 7 till 1 then 7 till 4 weekends and on a nightshift the car will do 40 hours

[Guest gs fan]

Hi totally agree with pinning the above and found the p.s bit very funny. Having spoke to the workshop supervisor at my local dealers and they are as just as sick with citroen as we are. Funny thing though is that the c5s i own dont seem to get as many faults as what is posted on this forum. Now while i would like to put it down to our brilliant mechanical skills i cant help wondering if its because these cars where designed to run and not little stop starts all the time. mine are on the road from 7 till 1 then 7 till 4 weekends and on a nightshift the car will do 40 hours

Maybe ??? But I'm not turning mine into a taxi to find out , couldn't stand the hours or the horrible drunk people , and I should know cause I'm often one of them !!

Mine has been great , 7 yo ,46,000 on it when I bought it 16 months ago 72,000 on it now , they don't rust ! Only troubles have been the hereditary rear brake problem and the weld on the engine side of the cat' failing which meant I had to replace the cat ( £167 from the net "cats4less")

All cars have their faults , a guy at work told me his BMW mini 54 plate had an electric motor which controls the power steering burn out and the replcement was £1300 and they charged him another 200 to fit it ,so they are all just money pits .

I really like the Citroen ride quality , when I drive anything else now I feel that its like being in an unsprung cart .

Thanks as ever for all the usefull info'...

[paul.h]

Yesterday I removed the loctite from the driver's rear caliper yesterday with the caliper still in place and learnt a bit more (previously I had just undone the bolts enough to clear the suspension arm on this caliper and the other one I had to remove completely before hammering out the bolts).

 

One caliper bolt was removed and the loctite drilled out of its caliper hole whilst the other was kept in place as in the above procedure so the caliper did not split.

 

Once a bolt is undone from the threads on the suspension arm it stopped moving out. After futile attempts with a hammer and also trying a bolt from the back of the suspension arm with the same thread (10mm x 1.25) to push out the bolts, I eventually successfully used a pry bar/crow bar to lever against the back of the bolt head (protected by a large washer) against the caliper whilst continuing to turn the bolt. Gradually the bolts moved out but it still took a lot of effort and time and it was then too late to bother removing the pads and cleaning up the back of the caliper. WD40 and brake cleaner were used in the small holes in the calipers but their benefit was not great (if any). The pry bar I have is a Draper one, L shaped with cut outs for nail removal so this helped keep it against the bolt. There is probably a puller that would make this job easy. The long 10mm drill was a masonary one since these are cheaper. The bolt hole is probably 11mm so the loctite also needed cleaning out with a file and long screwdriver so the bolt is a nice loose fit.

[Guest digitalinkjetman]

Had my pads out today because of the screeching everytime I braked!

 

They pulled out, upwards out of the caliper no problem.

 

Cleaned the back and copper greased them.

 

I assume were not supposed to remove the caliper its self unless were disk changing?

[DaveHerns]

Had my pads out today because of the screeching everytime I braked!

 

They pulled out, upwards out of the caliper no problem.

 

Cleaned the back and copper greased them.

 

I assume were not supposed to remove the caliper its self unless were disk changing?

Did the same to mine a while ago

I'd be inclined to leave the caliper untouched if no need , no point in making unnecesary work

[Guest C5buff]

Hello

I had much the same experience as everybody else with the rear brake calipers. It seems that it takes a few years for the corrosion problem to show up. With mine I had the usual wedge shaped wear on the pads and decided to take the calipers off. I used a long extension bar on my socket to remove the bolts, risking the bolt heads snapping off. I was lucky and they came undone enough to remove the calipers. Then with the caliper held in a vice it took an hour of working the bolts back and forth and hammering them to get the bolts fully removed, one at a time replacing with a nut on the end to prevent the caliper from splitting as you do the other one. Despite this one of my calipers did split. I found there was an oil seal inside the internal drillings which I took care not to damage. This caliper went back together ok with no fluid leaks.

I did what everyone else does, cleaned the corrosion off and fitted a gasket between the calipers and the suspension arm, with one exception; I decided to fit stainless steel bolts instead of the originals. These cost me 10 quid each and of course I needed four. I had them especially made as they are not standard. With these bolts I did not need the loctite throughout the length of the calipers as originally fitted by Citroen, which is the cause of difficulty in removing them (presumably used to prevent corrosion of the bolts inside the calipers)just only on the threads into the suspension arm. The new bolts were fitted in the calipers with a smear of grease and I intend to check them at each 12000 mile service which I do myself.

[paul.h]

Did you have any bother getting the correct bolt hardness grade in stainless steel, should be 10.9 where a standard high tensile bolt is only 8.8 ? I had to replace one bolt which snapped with a longer one so I could fit a nut on the end and could only get an allen cap head one at 12.9

[Guest C5buff]

Hello,

After removing the bolts I took them to an engineering firm, I explained the purpose of the bolts and asked them to make copies in stainless steel. They made them in A2 grade stainless. The bolts can take the load ok which is 70 nm, about the same as a wheel bolt. So fatigue should not be a problem. I fitted them ok, torqued them up and they are fine, although a bit pricey.

[paul.h]

Grade A2 stainless is the type/composition of the steel (also named as 304 stainless) which is one of the lower cost ones. Is there a number stamped on the head of the bolts which can be used to find out the tensile strength so it can be compared against the original 10.9 grade bolts ? Why I ask is if the new bolts have a lower tensile strength, effectively they will not be as strong and maybe they could shear in use. A quick search on the web indicates they may only have 2/3 the tensile strength of 10.9 bolts, in other words, it may be best to refit the originals until you have any better information.

[Guest C5buff]

Hello Paul,

I left the choice of steel to the engineering firm who knew what they were for. I remember the chap looking at some tables which I assume were his way of selecting the proper bolts. I am in Aus at the moment and the car is laid up. On my return I will check to see if they are marked on the end of the bolt as you mentioned. Thanks for pointing it out. 70 mn is not a very high load for bolts of this size, but still we need to be correct.

[Johndouglas]

70 mn is not a very high load for bolts of this size,

 

The same part number bolt is used on the Xantia's rear calipers and the torque figure for those is given as only 47Nm. I don't think you need be too fussed about them.

[paul.h]

I am not bothered about the torque setting of the bolt but the strength of the steel to hold the caliper against the forces of stopping the car. Looking at tables on the web, A2 bolts have a far lower yield and tensile strength than grade 10.9 bolts. Yield strength at which the steel deforms is typically about half and tensile strength at which the bolts break is typically about 2/3. In other words, under heavy braking, the bolts may snap and the calipers come loose - unless Citroen have large safety factors in their choice of bolts, and then if they were that large, they could have chosen a standard lower cost 8.8 grade bolt which still has higher strength than A2.

[Guest C5buff]

Hello Paul,

The points you make are valid and I will check when I get back from Aus. I did think at the time that I could have purchased new bolts from Citroen and have them Teflon coated or plastic coated or just painted. In the end I decided on the stainless as this will not suffer any surface scoring when screwing the bolts in which is likely to occur with the softer coatings mentioned.

It is not a good idea to refit the original bolts because they will already have been stretched with the caliper miss alignment due to the interface corrosion between the two metals.

That together with the very high breakout force needed to turn the bolts in order to get them out, in my view renders them unsuitable for further use.

Despite our efforts to remedy the problem and the long history of this matter Citroen still persist with it, which is in itself an incorrectly engineered assembly.

Citroen are however an innovative company particularly with the C5 suspension that one has to take on board the not so good bits to have an advanced car for less than you pay for the more expensive cars. Or not have one at all.

[Guest C5buff]

Hello Paul I am back from Aus and soon picked up the flue. I checked the marks on the end of the caliper bolts and it has A2 V70. I then went to my engineering works chappi and showed him your concerns about the tensil strength. He agreed with you that the stainless is much lower in shear strength. So we cannot recommend this grade of stainless bolt as a solution, is the short answer.

Individual owners can make up their own minds about this.

I take the view that the standard caliper bolts will be severely weakend by the force of the interface corrosion as they become stretched. On the other hand no one has reported any bolt failures. The stainless although weaker than the originals are still very strong, and that the car cannot develop the brakeing force necessary to shear them. Further more the brakeing effort on the rear wheels is much less than the front wheels.

We talked about refitting new Citroen bolts and instead of sealing with the loctite useing a sealant called RTZ which should do the same job, but enable the bolts to be removed easily in future, with loctite on the theads only.

So unless someone has a better idea it will be down to Citroen to sort it. I always was a foolish optimist.

[paul.h]

Welcome back. I used copper grease on the bolts to stop any corrosion between the bolt and caliper, not wanting to go through the bother of removing the loctite stuff every year or so.

Somebody else may comment/correct me, but since stainless steel is still a different metal to the alloy caliper, there may still be the possibility of galvanic corrosion occurring - as a minimum it may be worth putting a blob of high temperature grease/sealant on the loctite injection holes on the calipers to keep out moisture.

 

Interestingly, on the new C5 the design of the rear calipers has changed to similar to front ones with a single piston so without bolts going through the full width of the calipers and only the area of the bolt holes on the carrier is in contact with the suspension arm. The handbrake is also on the rear brakes.