Seized brakes, Hydraulic problem ?

[RGCorris]

After a few days of non-use I set out on the seven-mile run to the station one morning and noticed my series 2 XM auto estate seemed to be down on power and struggling. On arrival I noticed a burning smell reminiscent of brake linings. Having taken it to the local garage they report that both front brake callipers are seized; they have tried disconnecting the handbrake cable and that makes no difference.

It seems to me unlikely that both callipers would choose to seize at the same time, and I wonder therefore whether there is anything further up the hydraulic system that could be at fault, preventing the pressure releasing when the footbrake pedal is released. Any thoughts would be appreciated.

Richard

[noz]

Hi richard,

Your guess is correct. In the right hand drive Xm there is no room in the engine compartment for the master cylinder for the brakes as there is in the left hand drive version. Therefore, they put the master cylinder in the space at the bottom of the screen beside the window wiper motor. Unfortunately, in this location it is subject to all sorts of corrosion being in theline of fire for both rain and salt kicked up from the road surface. There is a two part linkage in there to translate the vertical motion of the pushrod from the brake pedal into the horizontal motion to push on the plunger on the end of the master cylinder. There is a pivot point to translate that through 90Deg. The pivot point can sieze or become very stiff such that the rematively light spring in the master cylinder cannot push the rod back to its default location. Luckily its a relatively easy problem to solve.

Remove the two plastic covers, one at either bottom corner of the screen. These can be difficult and are better warmed with a hair dryer first to reduce the likelihood of breaking the plastic clips behind the covers. Push down the way on the cover with the palm of one hand and pull outwards on the bottom of the cover with the other. As I say it can be a bit tricky but persevere, they will come off. Unscrew the two screws on either end of the scuttle panel and the single screw in the centre of the bulkhead. Lift off the scuttle panel manoevring it through the gap between the bonnet and the windscreen. At the drivers side you will see the master cylinder with the hydraulic pipes attached and at the other end of the cylinder will be the actuating rod and pivot.

If this is indeed the source of your trouble, try pushing down on the vertical pushrod thereby releasing the horizontal pushrod from pressing on the end of the master cylinder plunger. Make sure there is a gap between the rubber cover on the plunger and the flat hex end to the adjusting bolt. Now try to turn the wheels. If they now turn easily then this was the source of your trouble.

In the first instance, coat the pivot liberally in your favourite brand of release oil. If that does not work, remove the bolt through the middle of the pivot and remove from the car. Clean off all signs of rust, coat with an anti-rust agent, grease liberally and reassemble. Problem solved !

Please give us some feedback on how you got on and feel free to come back with any other questions you may have.

Cheers

noz

[kenhall1202]

One possible cause of binding brakes on the XM could be a lack of clearance between the cranked lever and the brake doseur valve rubber button or partial seizure of the lever itself. The exposed position of these items does not help.
Unfortunately inspection of the lever/doseur area requires removal of the scuttle below the windscreen after removing the plastic trim pieces at the upper rear of the wings.

Ken

Edit Noz beat me to it!!
PS I have noticed that thesite refresh/page load time since the host change is noticeably a lot faster - good move there Noz.

This post has been edited by kenhall1202 on September 20, 2012 03:47 pm

[RGCorris]

Thanks for the helpful advice - on removing the plastic scuttle the area underneath was filled with leaves, twigs, nuts and general sludge, and after scraping it clear of the brake pivot and working the pedal a few times it freed off the calipers. The garage was a bit embarrassed and declined to bill me (not least because I had done most of the work in removing and replacing the plastic panels). Took it home and hosed out the whole area and removed all the accumulated debris, let it dry out and then sprayed the brake pivot area with WD40. We have since undertaken a 500-mile round trip without a recurrence so I think that has solved it.

Richard

[techmanagain]

Mention is made of hosing out the area in question. This may have allowed water to go down the air intake for the heater motor (at the passenger side) and this could have entered the heater motor, shorting out the motor control circuit board.
If the motor still operates correctly, you can breathe again and remember not to hose it out again! If not, attention must be given to the motor assembly which may require replacement or repair of this little circuit board. (Don't ask how I know!)