Xantia brake probs

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Johnno
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Xantia brake probs

Post by Johnno »

My 2.1TD VSX has an unusual symptom whereby the brakes have a delay in operation, noticeable at low speeds, making it very easy to overbrake. Additionally, the brakes bind for a few seconds after the pedal is released.
There is quite a bit of dive under braking as well - possibly a function of the lack of feedback from the pedal leading to the aforementioned overbraking, but I have driven a friend's Xantia SX 2.1 which doesn't have these effects.
Could this be the doseur valve? The vehicle does seem to sink more rapidly that it should and I have read in these pages that the doseur valve is connected to the rear brake circuit via the anti-sink sphere.
Any ideas anyone? I'll be pressing my venerable BX (luvverly brakes, boyo) back into service until the Xantia is sorted.
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bxbodger
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Post by bxbodger »

It shouldn't have any dive at all, no matter how hard you are braking!
Any dive points to the rear brakes not working -have you had any rear brake or suspension work done recently, as dive is what happens if the rear brakes aren't bled through.
My suggestion would be to start by bleeding the rear end and seeing if this makes a difference-jack up, remove rear wheels, set the suspension on high and open the nipples with the motor running- you should get a good flow of LHM-if not you will have to stert looking further up the line and check the doseur.
See what happens with the bleeding first, though.
Johnno
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Post by Johnno »

The discs and pads have been renewed (in December) and I bled the brakes about 6 weeks ago. There was a little air in the rear circuit but not the front. I'll try again this weekend, to ensure that there is no ingress.
The other (possible unrelated) symptom is what can only be described as a short "groan" from the pedal area when the brakes are initially applied. This generally ceases after the first two/three applications.
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AndersDK
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Post by AndersDK »

John -
Your description of symptoms points to an air problem in the hydraulics system. Air takes time to compress by the hydraulic system, when pressure is applied to brakes on demand by your brake foot.
I've done these 3 write up's to help DIY'ers getting around the most common problems on hydraulic Citroen models :
First vent the hydraulic suspension, doing the Citaerobics, then Bleed the brakes. Finally it's well worth considering the LHM fluid service.
The Xantia brake pedal is renowned for strange behaviour because of the spring rod fitted between pedal and doseur valve.
Could be here you have the problem.
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Post by RichardW »

You have almost certainly got a sphere that is leaking gas into the brake system - bet you will find some gas in there if you bleed the brakes again. Probably need to change all 4 rear spheres to cure.
Xantia brakes seem to give the buzz / groan occasionaly - especially after they have been given some abuse by the MOT man!
Johnno
(Donor 2022)
Posts: 154
Joined: 18 Feb 2004, 18:02
Location: Milford, Godalming
My Cars: C5 2.2 VTR + Nav 173
Mazda 6 2.2 Sports Nav Estate
Jaguar 3.8 MkII 1961
Ex 2007 C5 2.2 Estate
Ex 2003 C5 2.2 Estate
Ex Xantia 2.1 TD Exclusive
Ex BX 1.7 DTR
Ex BX 1.9 TRS
x 1

Post by Johnno »

Thanks, guys. The idea of a sphere leaking gas is an interesting one, and I wouldn't have considered that. Given the link with the rear circuit, I assume that it would most likely be the anti-sink sphere? However, given that the spheres have almost certainly not been changed for a considerable time, it probably wouldn't hurt (except in the wallet department) to change them all.
I've done the Citaerobics before (takes a long time with these low capacity pumps!) but I've never flushed the system, and I doubt the previous owner did either.
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