Xantia, no brakes

sv4195 · Post by **sv4195** » 01 Apr 2003, 20:11

M Xantia 1.9TD VSX, Hydractive, A/C, 160K)
On starting after being stood, sometimes for not long, and you set off as soon as the engine fires there are no brakes. Pressing the pedal results in enough time to think "Oh my ***, death trap" and then you stop abruptly. To me, it also feels as tho' the back end is 'hard' altho' that might be paranoia.

Suspension and brakes OK otherwise. Only the 4 'suspension' spheres have been replaced since 50K, when I got it.[:I]

tomsheppard · Post by **tomsheppard** » 01 Apr 2003, 20:17

I don't think that you are supposed to set off as soon as the engine fires because, hydractive or no, there needs to be hydraulic pressure present. If you are losing all brake pressure overnight, you may have a dodgy accumulator sphere. Most of the old hands on this site advocate changing it with the others.

Post by **Jon** » 01 Apr 2003, 20:19

I'd guess that the accumulator sphere is so "flat" that there is no reserve pressure left it it if the car has been left overnight.By setting off "as soon as the engine fires" you are not allowing the system enough time to pressurise.
I would suggest initially that a new Accumulator is fitted, and the system is bled. It is also almost certainly likely that the centre front and centre rear spheres require renewal and this is contributing to this "problem".

sv4195 · Post by **sv4195** » 01 Apr 2003, 20:35

I mentioned "as soon as the engine fires" to get you all thinking, its really "after you've put your seat belt on". I agree you have to let the old girl pump up a little but this problem seemed to just happen.
Will fit front and rear centres and accumulator spheres. Now should I buy from AS for £19.25+ or genuine for £25+. Am tempted to replace accumulator, centre, hydractive, anti-sink and flush/refill, what do you guys think or is it a case of 'if it aint broke ..'

tomsheppard · Post by **tomsheppard** » 01 Apr 2003, 20:49

Buy from AS with confidence, I have been happy with the parts. Replace spheres, read the many useful postings. Flushing is not likely to solve the problem and could involve much time and aggravation. I would follow jon's advice and swap out the accumulator first. Flush it when you have cured the problem.

Dave Burns · Post by **Dave Burns** » 02 Apr 2003, 02:13

You must be driving away before the stop and hydraulic pressure lights are out, if so this behaviour is to be expected.
Dave

sv4195 · Post by **sv4195** » 02 Apr 2003, 04:14

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Dave Burns

You must be driving away before the stop and hydraulic pressure lights are out, if so this behaviour is to be expected.
Dave<hr height="1" noshade id="quote"></blockquote id="quote">
Oh no I'm not. They go out almost immediately - as I said earlier its really when you have spent time doing up your seat belt so I do give it chance to 'pump up' its just that this symptom sort of suddenly appeared.

Dave Burns · Post by **Dave Burns** » 03 Apr 2003, 00:06

Well then you have a fault there of some sort, when those particular lights go out the brakes should have adequate pressure available for correct operation.
Dave

sv4195 · Post by **sv4195** » 06 Apr 2003, 23:02

It seems like a new accumulator has solved the problem. Thanks chaps.
Now planning new centre spheres and flushing (and dash lights, and carpet, and major service, and ...)

sv4195 · Post by **sv4195** » 19 Apr 2003, 18:37

Hmmm, sorry to resurrect this thread but its doing it again (only accumulator changed). The 'stop' lights take longer to go off than before accumulator changed. I haven't tested it yet as I have been having more chemo (5 days in hospital) but I'll get to it when I feel up to it.
Do we think the changing the centre spheres will affect anything?

JohnD · Post by **JohnD** » 19 Apr 2003, 19:33

If your accumulator was flat and you've now changed it, the stop light will take longer to go out.

sv4195 · Post by **sv4195** » 20 Apr 2003, 03:11

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by JohnD

If your accumulator was flat and you've now changed it, the stop light will take longer to go out.<hr height="1" noshade id="quote"></blockquote id="quote">I realise the lights will take longer to go out. What I really meant to say[:I] is that the brake problem appears to have returned i.e. if I set off immediately after the lights have extinguished following being stood (overnight) there are no brakes until, it seems, something has 'pumped up'. Reversing down the short, steepish drive does get the adrenelin going.
I did read in another thread that the rear suspension and brakes are linked; the rear suspension does seem to be reacting as if it isn't quite fully operational in the first few moments of running (when we have little or no brakes).
From my limited knowledge I would not suspect the anti-sink sphere as the car doesn't sink but what does the consensus think? Once running everything seems to be hunky dory, brakes are keen (even with pedal spring) and suspension seems to work OK, maybe a touch firm at the rear, although I am now paranoid about the anti-roll bar drop links, the last pair lasted 2000 miles (I got a refund from the motor factors).

alexx · Post by **alexx** » 20 Apr 2003, 03:55

Rear brakes get the pressure from rear suspension, but there is an anti-sink valve in between. Since your car has done considerable mileage, I presume that after staying overnight, pressure in anti-sink sphere, which is in fact accumulator sphere for rear brakes, drops to zero, because of internal leakage in brake dosieur valve. So, rear brakes will become operational after anti-sink valve opens, and this one will open after the security valve opens (it's when the pressure in main accumulator sphere reach about 80 bar). At that point, you have only about half of braking power. A few seconds later, working pressure in main accumulator will reach it's working range (145-170 bar), and full braking power will be established.
If brakes become fully operational 10-15s after turnig the engine on, I think there's nothing to worry about.