Hi All
Thanks to this site I've solved quite a few probs, but am a bit stuck on this one.
I'm about to change all 4 spheres on my Xantia TD, even though they appear OK doing a bounce test, as the ride has become very hard and rattly.
However, sometimes when I'm sat with my foot on the brakes, at traffic lights for instance, the back end will suddenly drop, then rise again when I take my foot off the brake to pull away.
It has also started to drop at the back end with a whistling sound when I stop the engine, but does not drop when the car is fully loaded with all my disco gear in it.
So, do I also need to replace the rear accumulator sphere, or is it more likely to be the anti sink valve.
Any help much appreciated before I spend more money than I need to.
Paul
Xantia TD Hydraulics
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Before you go replacing spheres, check whether the suspension height is correct. If it is correct and the ride is hard it needs new spheres. The suspension on a Xantia can get stuck too high or too low, its usually obvious if this has happened.
The sinking when you hold the car on the brakes is normal for a Xantia, the reason why is complicated but I'll try to explain why.
The wheelbase of a Xantia varies with suspension height (it gets shorter when the rear suspension goes up) and when you brake it makes the rear suspension go up. When you stop and hold the car on the brakes, you are using the brakes to keep the wheelbase "short" and keep the rear suspension high, the height corrector will try to compensate for this and get the suspension height back to the right height. As the height corrector releases rear suspension pressure, it expects the rear of the car to fall, but it cant fall because the brakes are holding it. One of two things will then happen, either the brake pressure won't be enough to hold the suspension height i.e. far too much rear suspension pressure is lost and the brakes can't hold up all of the weight of the car so it falls. Or you take your foot off the brake and the suspension falls again because it has lost too much pressure. In either case this is normal behavior for a Xantia, the solution is to not hold the car on the foot brake, and use the handbrake instead (you'd fail your driving test if you did't use the handbrake).
I'm not sure about the car sinking when you stop the engine, this could be a problem with an anti sink valve, brake valve or a height corrector rather than being a straight forwards accumulator sphere problem. Sometimes when you've got this sort of valve problem it can be remedied by having the LHM system flushed (replace LHM with Hydraflush or equivilent, drive 1500miles replace with new LHM).
The sinking when you hold the car on the brakes is normal for a Xantia, the reason why is complicated but I'll try to explain why.
The wheelbase of a Xantia varies with suspension height (it gets shorter when the rear suspension goes up) and when you brake it makes the rear suspension go up. When you stop and hold the car on the brakes, you are using the brakes to keep the wheelbase "short" and keep the rear suspension high, the height corrector will try to compensate for this and get the suspension height back to the right height. As the height corrector releases rear suspension pressure, it expects the rear of the car to fall, but it cant fall because the brakes are holding it. One of two things will then happen, either the brake pressure won't be enough to hold the suspension height i.e. far too much rear suspension pressure is lost and the brakes can't hold up all of the weight of the car so it falls. Or you take your foot off the brake and the suspension falls again because it has lost too much pressure. In either case this is normal behavior for a Xantia, the solution is to not hold the car on the foot brake, and use the handbrake instead (you'd fail your driving test if you did't use the handbrake).
I'm not sure about the car sinking when you stop the engine, this could be a problem with an anti sink valve, brake valve or a height corrector rather than being a straight forwards accumulator sphere problem. Sometimes when you've got this sort of valve problem it can be remedied by having the LHM system flushed (replace LHM with Hydraflush or equivilent, drive 1500miles replace with new LHM).
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