can anyone assist?
'95 XM 2.5TD
My MOT is up but my parking brake will never pass. The problem seems to be that 2/3 of my pedal travel does nothing. If I disconnect the cable from the carrier and operate the lever by hand it has about 15mm of travel in total at the end of the arm. 10mm of the 15mm has no effect and is very easy to move. Only in the last 5mm does the piston start to act on the pads and grip the disc.
I suspect the self adjusting mechanism inside the caliper is not working. However, it is constantly bathed in LHM and unlikely to be seized by rust or the like. The small bore piston on which the arm acts seems to move very freely. I've taken the rubber boots off and inspected the exterior mechanism. It is all well greased and the return springs look in good order and operate correctly.
Can anyone measure the amount of movement they have and let me know before I go taking the piston out of the caliper.
All of the above pertains to both sides.
Any help would be appreciated.
cheers
norrie
parking brake caliper
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jeremy
- Posts: 3959
- Joined: 20 Oct 2002, 16:00
- x 2
If the mechanism is like that on a Bx then the handbrake can often be persuaded to adjust by pressing quite hard on the footbrake (with the engine running) and then operating the handbrake firmly a few times.
I expect you have tried this in which case I wonder if your cables are set up according to specification. The free play sounds excessive and I wonder if the initial adjustment was made correctly.
jeremy
I expect you have tried this in which case I wonder if your cables are set up according to specification. The free play sounds excessive and I wonder if the initial adjustment was made correctly.
jeremy
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AndersDK
- Posts: 6060
- Joined: 21 Feb 2003, 04:56
- x 1
Hi Norrie -
The XM, Xantia & BX front calipers are of the same construction as far as I read schematics.
From the BX I know by painfull experiences that the parking/hand brake mechanism in the caliper can be a dry rusty mess - oustside the LHM area. This is the part of the mechanism that resides under the rubber protection cap 'round the caliper lever arm.
Problems here make the mechanism stick - reluctant to react on the usual automatic adjusting procedure.
It's a matter af removing the caliper an overhaul it. Rarely you need new parts - as it's simple cleaning and greasing that does the trick.
Depending on your attitude - you may want to use a rep kit containing new rubber O-rings, cap, cap retainer & slide bushings (for caliper body) - while you're there anyway.
Only in severe cases I've found a rep kit necessary - the whole caliper construction makes it friendly and easy to overhaul & make work fine again. It's a geniuos little piece of reliable construction - compared to what I've seen on other car makes.
The XM, Xantia & BX front calipers are of the same construction as far as I read schematics.
From the BX I know by painfull experiences that the parking/hand brake mechanism in the caliper can be a dry rusty mess - oustside the LHM area. This is the part of the mechanism that resides under the rubber protection cap 'round the caliper lever arm.
Problems here make the mechanism stick - reluctant to react on the usual automatic adjusting procedure.
It's a matter af removing the caliper an overhaul it. Rarely you need new parts - as it's simple cleaning and greasing that does the trick.
Depending on your attitude - you may want to use a rep kit containing new rubber O-rings, cap, cap retainer & slide bushings (for caliper body) - while you're there anyway.
Only in severe cases I've found a rep kit necessary - the whole caliper construction makes it friendly and easy to overhaul & make work fine again. It's a geniuos little piece of reliable construction - compared to what I've seen on other car makes.
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Doc
- Posts: 150
- Joined: 30 Dec 2002, 04:11
Hi Noz
My XM 2.1 TD failed on the exact problem in January. To adjust your parking brake first check for obvious damage such as frayed, snapped or incorrectly routed cables.
Assuming the cables are ok,
1)With the engine running, press the brake pedal a few times to allow the adjustment mechanism to operate within the caliper.
2)Switch off and raise car and support it on axle stands and chock rear wheels.
3)Next push the park brake release to the locked position. Depress the park brake pedal to the 4TH NOTCH of its travel.
4)At one of the calipers, loosen cable adjuster locknut then turn adjuster-nut to obtain a balance BETWEEN the cable lengths AT THE EQUALISER of about 1.5mm. If necessary repeat the procedure on the other caliper and recheck the cable lengths on the eqaliser again.
5)Release the parking brake and it should return to its rest position.
6)Return to the caliper and make sure the parking brake operating levers on the calipers are NOT pulled by the cables even when the steering is turned lock to lock.
7)If they are ok, tighten up the cable adjuster locknuts on the calipers. Press the parking brake pedal several times (without locking it) and make sure it comes to its rest position.
8)Check to see if parking brake is fully applied by pressing the pedal between 6 and 12 clicks.
Hope this helps.
My XM 2.1 TD failed on the exact problem in January. To adjust your parking brake first check for obvious damage such as frayed, snapped or incorrectly routed cables.
Assuming the cables are ok,
1)With the engine running, press the brake pedal a few times to allow the adjustment mechanism to operate within the caliper.
2)Switch off and raise car and support it on axle stands and chock rear wheels.
3)Next push the park brake release to the locked position. Depress the park brake pedal to the 4TH NOTCH of its travel.
4)At one of the calipers, loosen cable adjuster locknut then turn adjuster-nut to obtain a balance BETWEEN the cable lengths AT THE EQUALISER of about 1.5mm. If necessary repeat the procedure on the other caliper and recheck the cable lengths on the eqaliser again.
5)Release the parking brake and it should return to its rest position.
6)Return to the caliper and make sure the parking brake operating levers on the calipers are NOT pulled by the cables even when the steering is turned lock to lock.
7)If they are ok, tighten up the cable adjuster locknuts on the calipers. Press the parking brake pedal several times (without locking it) and make sure it comes to its rest position.
8)Check to see if parking brake is fully applied by pressing the pedal between 6 and 12 clicks.
Hope this helps.
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crooser
- Posts: 166
- Joined: 08 Feb 2003, 12:08
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Doc
- Posts: 150
- Joined: 30 Dec 2002, 04:11
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noz
- Posts: 118
- Joined: 05 Mar 2003, 03:33
Thanks for the replies guys,
I'll have a go at the cable thing no matter which method I use but I don't think the problem lies there.
The pivot arm on the caliper has 15mm of movement from fully off to fully on measured at the end of the arm. 10mm of this movement does nothing. To me that means the self adjusting mechanism inside the caliper is not self adjusting. I would expect almost no movement required, maybe 2-3mm, before the pads start to be pressed against the disc.
Both cables are free enough and pull the pivot arms through all of the required travel.
Has anyone taken the piston all the way out to check the inner workings?
Since the weather's beautifull in Scotland this morning, I think I'll have a go and see what happens.
cheers
noz
I'll have a go at the cable thing no matter which method I use but I don't think the problem lies there.
The pivot arm on the caliper has 15mm of movement from fully off to fully on measured at the end of the arm. 10mm of this movement does nothing. To me that means the self adjusting mechanism inside the caliper is not self adjusting. I would expect almost no movement required, maybe 2-3mm, before the pads start to be pressed against the disc.
Both cables are free enough and pull the pivot arms through all of the required travel.
Has anyone taken the piston all the way out to check the inner workings?
Since the weather's beautifull in Scotland this morning, I think I'll have a go and see what happens.
cheers
noz
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Doc
- Posts: 150
- Joined: 30 Dec 2002, 04:11
Hello from slightly overcast Cambridgeshire.
I noticed the same amount of travel on the pivot arms on my XM but after adjustments on the cable lengths the handbrake works ok and holds the car(enough for an MOT pass). I think the amount of travel is normal. Are the rubber covers around the park brake mechanism intact? Any damage to these would allow dirt to 'gum up the works'.
Pump the brake pedal a few times to place the pads against the discs. This should take up any slack before commencing cable adjustment. If you do strip down the park brake mechanism, make sure the area is completely clean and free of corrosion.
I noticed the same amount of travel on the pivot arms on my XM but after adjustments on the cable lengths the handbrake works ok and holds the car(enough for an MOT pass). I think the amount of travel is normal. Are the rubber covers around the park brake mechanism intact? Any damage to these would allow dirt to 'gum up the works'.
Pump the brake pedal a few times to place the pads against the discs. This should take up any slack before commencing cable adjustment. If you do strip down the park brake mechanism, make sure the area is completely clean and free of corrosion.
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crooser
- Posts: 166
- Joined: 08 Feb 2003, 12:08
noz.i bought mine about 2 years ago complete with[unknown to me] a cracked head.local garage put a new head on and it lasted a year,then i did it myself and put the head on dry, no good so i took it all off again,new bolts and new gaskets again but this time i used wellseal and it's been okay since.i had the pump and injectors done but they must have done something wrong to the pump because the fuel computer is reading wrong.
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AndersDK
- Posts: 6060
- Joined: 21 Feb 2003, 04:56
- x 1
I've done numerous BX calipers [:D]
As I wrote up the thread - they are not that frightening to disassemble - and easy to make function again - once cleaned & lubed.
The Haynes BOL talks about aspecial tool for dis/re -assembly of the disc springs - but it's not needed if you have a well equipped DIY shop - and experience with mechanical bits under spring load.
The cable lever arm works on an actuator rod that goes all the way thru the caliper - reaching into the piston where it mates the actual self adjuster bits.
Where the rod penetrates the caliper body - a simple rubber O-ring is the leak proof element - very efficient - as the grooving for this O-ring makes it seal even better with system pressure applied.
Especially this O-ring I've NEVER had to replace - and the caliper NEVER leaked after my fiddling.
As I wrote : it's a frindly and well constructed brake caliper [8D]
First time it takes some cursing & head scratching to figure out how to overcome the rather heavy spring loaded bits - but once you get the idea after some trial & error - you see the light [:)]
I cleaned all bits with petrol - then immedately greased with LHM to stop the quick build up of stain on steel bits. The bits residing out of the LHM area are greased & stuffed with heavy ballbearing grease - i.e. the cavity with the spring discs under the cap is filled up with grease.
I suppose it would be more "correct" to use ALU-paste because of the risc of heating the caliper body during heavy breaking.
A word of caution :
The hub mating surface around each bolt hole for the caliper slide bushings must be clean & even - to avoid the bushings tilting a bit - when caliper is refitted.
I use a flat file placed squarely over both bolt holes on hub to clean/rub the bushings mating surfaces.
As I wrote up the thread - they are not that frightening to disassemble - and easy to make function again - once cleaned & lubed.
The Haynes BOL talks about aspecial tool for dis/re -assembly of the disc springs - but it's not needed if you have a well equipped DIY shop - and experience with mechanical bits under spring load.
The cable lever arm works on an actuator rod that goes all the way thru the caliper - reaching into the piston where it mates the actual self adjuster bits.
Where the rod penetrates the caliper body - a simple rubber O-ring is the leak proof element - very efficient - as the grooving for this O-ring makes it seal even better with system pressure applied.
Especially this O-ring I've NEVER had to replace - and the caliper NEVER leaked after my fiddling.
As I wrote : it's a frindly and well constructed brake caliper [8D]
First time it takes some cursing & head scratching to figure out how to overcome the rather heavy spring loaded bits - but once you get the idea after some trial & error - you see the light [:)]
I cleaned all bits with petrol - then immedately greased with LHM to stop the quick build up of stain on steel bits. The bits residing out of the LHM area are greased & stuffed with heavy ballbearing grease - i.e. the cavity with the spring discs under the cap is filled up with grease.
I suppose it would be more "correct" to use ALU-paste because of the risc of heating the caliper body during heavy breaking.
A word of caution :
The hub mating surface around each bolt hole for the caliper slide bushings must be clean & even - to avoid the bushings tilting a bit - when caliper is refitted.
I use a flat file placed squarely over both bolt holes on hub to clean/rub the bushings mating surfaces.
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noz
- Posts: 118
- Joined: 05 Mar 2003, 03:33
Thanks for that Anders,
You're right the spring washers are a little difficult. I don't have a bench press so I used my pillar drill and removed the circlip. I dismantled the entire contents of the piston and found out how it works. There's a spring which fits neatly around a short shaft. This allos the shaft to rotate in the direction of the spring opening. If you try to rotate the shaft towards the spring closing then it grips on the shaft and prevents it turning. This explains why you have to rotate the piston as you push it back into the caliper.
I've reassembled the drivers side and am about to refit the caliper to the car. Once bled and complete I'll do the other side. When I've got that in pieces I'll photograph the components which makes for an easier understanding of how it works.
Thanks for now, I'll be back later with an update.
cheers
noz
You're right the spring washers are a little difficult. I don't have a bench press so I used my pillar drill and removed the circlip. I dismantled the entire contents of the piston and found out how it works. There's a spring which fits neatly around a short shaft. This allos the shaft to rotate in the direction of the spring opening. If you try to rotate the shaft towards the spring closing then it grips on the shaft and prevents it turning. This explains why you have to rotate the piston as you push it back into the caliper.
I've reassembled the drivers side and am about to refit the caliper to the car. Once bled and complete I'll do the other side. When I've got that in pieces I'll photograph the components which makes for an easier understanding of how it works.
Thanks for now, I'll be back later with an update.
cheers
noz
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AndersDK
- Posts: 6060
- Joined: 21 Feb 2003, 04:56
- x 1
My rusty old brain now suddenly remember that Shane (DoubleChevron) did a couple of nice pix on the BX front brake caliper work :
http://www.aussiefrogs.com/shane/bx/bx_handbrake.htm
- enjoy !
http://www.aussiefrogs.com/shane/bx/bx_handbrake.htm
- enjoy !
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noz
- Posts: 118
- Joined: 05 Mar 2003, 03:33
Thanks Anders,
The XM handbrake isn't exaclty the same, it has more parts but the key element, the spring around the short shaft is identical.
However, I didn't find anything wrong with mine. No broken springs. My only slight concern was that the shaft did not rotate very easily inthe spring. The only thing that rotates the spring when working is the rotart force generated by the helix thread on the acuating arm. As you release the handbrake the rod retracts. The piston retracts slower than the rod so there's some relative movement. This movement is translated into rotary movement on the helix. As the short shaft rotates it moves on the actuator rod taking up the slack in the mechanism.
I also deduced from the parts once I had broken them down was that the automatic adjustment takes place when the handbrake is operated not the footbrake as some people have suggested. The total amount of movement due to the footbrake is probably 1mm at most. The movement due to the handbrake especially when not adjusted correctly is several mm. SO the footbrake does almost nothing for the self adjuster.
An interesting discovery is that the brake fluid pressure acts on the actuator rod as well as the piston. This force, which is rotated through 90 degrees at the pivot, means application of the footbrake will tend to return the parking brake cable to it's fully stretched position.
I've run out of daylight to do the other side today and its also baltic outside. Maybe I'll manage to do the other side next weekend. I'll also take some photos. Thanks for the help anyway.
cheers
noz
The XM handbrake isn't exaclty the same, it has more parts but the key element, the spring around the short shaft is identical.
However, I didn't find anything wrong with mine. No broken springs. My only slight concern was that the shaft did not rotate very easily inthe spring. The only thing that rotates the spring when working is the rotart force generated by the helix thread on the acuating arm. As you release the handbrake the rod retracts. The piston retracts slower than the rod so there's some relative movement. This movement is translated into rotary movement on the helix. As the short shaft rotates it moves on the actuator rod taking up the slack in the mechanism.
I also deduced from the parts once I had broken them down was that the automatic adjustment takes place when the handbrake is operated not the footbrake as some people have suggested. The total amount of movement due to the footbrake is probably 1mm at most. The movement due to the handbrake especially when not adjusted correctly is several mm. SO the footbrake does almost nothing for the self adjuster.
An interesting discovery is that the brake fluid pressure acts on the actuator rod as well as the piston. This force, which is rotated through 90 degrees at the pivot, means application of the footbrake will tend to return the parking brake cable to it's fully stretched position.
I've run out of daylight to do the other side today and its also baltic outside. Maybe I'll manage to do the other side next weekend. I'll also take some photos. Thanks for the help anyway.
cheers
noz