Brake problem on 1995 xantia

nigel c · Post by **nigel c** » 17 Jun 2003, 18:01

My brakes on the above car are a little erratic, if slowing down gently with only light pedal pressure, the brakes seem to go on and off on thier own. I've changed the pads and disks, and a garage is now saying to change the LHM and filters at a cost of around £70.
1) Do the guru's out there think that this is the problem ?
2) How easy is is to do it my self and what do I have to do ?
TTFN
Nige

Post by **RichardW** » 17 Jun 2003, 18:10

Nigel,
£70 to change the LHM and clean filters - I think I'll change jobs (although if that included an hour to bleed all the brakes maybe it's not so bad)! I think what you are experiencing is 'normal' for a Xantia - it's to do with the spring they fitted between the pedal and brake valve to make the pedal 'feel more normal' - causes all sorts of odd effects. If it hasn't been done changing the LHM will probably improve the feel of the brakes, and may improve the ride as well. However to cure the odd pulse you need to remove the spring on the back of the pedal - I haven't done it, so will leave it to others to explain what to do.
Richard

Homer · Post by **Homer** » 18 Jun 2003, 02:30

Have you checked the back brakes?

nigel c · Post by **nigel c** » 18 Jun 2003, 17:37

I have thought of checking the rear brakes, the disks and pads have loads of wear left on them, then I tought they might not be working
any Ideas of how to test them ??

JohnD · Post by **JohnD** » 18 Jun 2003, 23:44

Nigel - Unless your car is carrying a reasonable load the rear brakes won't work. If you never have it loaded, there's a danger of the rear calipers seizing. When I first owned a hydropneumatic Cit, the mechanic who usually does my MOT advised me to carry a bag of sand in the boot from time to time. If you've changed the pads and discs yourself, you shouldn't find any difficulty in changing the LHM and cleaning the filters. It's been covered loads of times. You'll find it in the search facility.

nigel c · Post by **nigel c** » 19 Jun 2003, 17:42

I've just been browsing the site and someone mentioned the time between ticks on the sphere being a sign of condition.
Mine ticks every 5 - 6 seconds, is this a sign that it's knackered and could this be causing the breaking problem ?

alexx · Post by **alexx** » 19 Jun 2003, 18:56

Rear brakes should work with and without load, only maximum braking force on the rear is lower if the car is empty, because of lower pressure in rear suspension.
Nigel, may I suggest the following experiment.
With engine running, move height lever to lowest position. If the car has anti-sink, wait a minute or two, until anti-sink sphere is empty. Now, suspension is depressurised and rear brake circuit is without pressure supply. Than, try the brakes. So, you will find out is the problem in front or rear brakes, because only front brakes will be working.
Do it on a VERY smooth road, since you will be without suspension. And another note, in that condition, brake pedal will react somewhat differently, because braking force is regulated with rear suspension pressure (higher the load, higher the braking force on both front and rear brakes, with the same force applied to brake pedal).

ghostrider · Post by **ghostrider** » 19 Jun 2003, 19:03

certainly if you are not turning the steering wheel or pressing the brake pedal it should go longer between the regulator cutting in and out, I seem to remember one of the guys at Pleiades saying you should be able to press the brake pedal a few times without the regulator cutting in, I have a feeling that this test was to done with the suspension in the high position to take wear in the height correctors out of the equation. The sphere in question being the main accumulator on the end of the regulator of course

Pete
________
Xt 125 R

alexx · Post by **alexx** » 19 Jun 2003, 19:10

Since the car is '95, it should have 6+2 HP pump with separate circuit for power steering, so turning the wheel shouldn't make any difference.

ghostrider · Post by **ghostrider** » 19 Jun 2003, 20:50

alexx does the output of the pump for the pump to the steering go through a separate regulator? I've not been able to find any hydraulic layouts for the Xantia, I see the Haynes manual does a massive body swerve round the whole thing! Perhaps they should sign for Real Madrid as well

))
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Honda SMX specifications

jeremy · Post by **jeremy** » 19 Jun 2003, 21:27

6 seconds is far too rapid for the clicks regardless of the pump fitted. I expect your accumulator sphere has failed (life expectancy 3 years. there are many testes but try turning off the engine and sitting on the boot lip/back bumper. car should drop and after a while raise itself as the accumulator responds to the height corrector. Note the lift will not be immediate - there is a delay in the height corrector. As a matter of interest my BX TD does this while I fill it with a full tank of fuel - as I get near the top of the tank the car rises quite noticeably.
The ball bearing non-return valve in the regulator may need re-seating as well. Its quite simple to do and the result on 2 regulators on my car has been a change from about 9 seconds to a very long time using the same sphere.
If the acumulator is not functioning properly the braking force is being generated by the pump as required which may be why you are getting the problems you describe. A flat accumulator will also damage the pump eventually.
jeremy

akojic · Post by **akojic** » 19 Jun 2003, 23:01

Jeremy where is placed non-return valve and what is its main purpose. I have got Xantia 1.8i 8V L reg (I supose) and would like to know litle more about this valve. Re-seating procedure is it complicated and is it DIY job? Thanks

Dave Burns · Post by **Dave Burns** » 20 Jun 2003, 03:03

Pete there is no regulator involvement or any other device concerning the power steering supply from a 6+2 pump as on your car, the output from the 6 pistons of the pump goes direct to the pinion valve on the steering rack, the other 2 pistons feed the suspension and brakes via the regulator/accumulator.
The oil continously being delivered to the steering rack goes through the pinion valve and back to the reservoir, thus the system is completely at idle when there is no demand for power assistance, on turning the wheel the pinion valve directs the oil to one or other side of the piston in the steering ram, forcing it and the rack in the desired direction.
Dave

alexx · Post by **alexx** » 20 Jun 2003, 12:14

Exactly! There is no external regulator, but a pressure limiter ball valve exist, and it is inside the 6+2 pump (it was previously in the flow distributor).
When there is no demand for power assistance, LHM is just circulating through the pump (its power steering half) and the pinion valve, and there is no pressure in that circuit. Turning the wheel to one side results in building of the pressure on one side of the steering ram, the pressure being roughly proportional to the force applied to the wheel.

nigel c · Post by **nigel c** » 20 Jun 2003, 13:25

Responding to Jeremy's comments - my rear suspension drops when I fill the tank.
Also please cn you ***lain how to reset the ball bearing non-return valve in the regulator - I'll have a go at this at the weekend.
Thanks
Nigel