Wrong sphere? HDI estate

[isisalar]

Afternoon chaps
Trying to get to the bottom of why the car won't respond to a sit in the boot test very well if at all without the engine running. I fitted a new GSF main accumulator sphere recently and thought it was worth checking if it was the correct one. After a bit of fun with a mirror and a camera I found the part no. 453pc0260. The correct one for my car according to their website is 453pc0011. Putting in the 0260 no. shows it to also be a 70 bar accumulator sphere but with a height 15 mm higher than the 0011. I suppose this indicates a bigger capacity.
Could this have any bearing?
Just went out to check after the car had been off for 1/2 hr, no response at all, not a flicker, the car hardly lifted at all when I got out, had sunk normally when I sat in. 8 seconds after starting the engine it's back up to normal height.
Accumulator is ticking at something over 2 minutes and all the sphere's seem good on the road. Replacement rear height corrector well lubed and working well.
Simon (Mandrake) had a theory that electrovalves sticking open or closed may be involved when we were discussing what turned out to be the broken height corrector and this was one of the symptoms mentioned, could this be something to check out? Doesn't feel like there's any harshness to the suspension now.
Since driving the wife's Saxo for a few miles the other day the Xantia is feeling super super smooth. Must drive the Saxo more often.
Cheers
Paul

[CitroJim]

No, that won't have any bearing at all Paul, what you have there is a 70 bar 450cc front centre detractive sphere and is in fact better than a standard 400cc 62 bar accumulator as it has more capacity.

It sounds like all is good with the engine running and a 2 minute tick suggests there's no internal leakage problems. It may be that the anti-sink valves are popping into action really quickly and thus preventing the sit in the boot test working.

You can prove this by stopping the engine, closing all doors and tailgate and immediately start bouncing the rear. It should be soft. If it starts off soft and goes hard well before 30s have elapsed (the hydractive time-out) then the anti-sink valves are working very quickly.

Of so then no worries as it's just a sign that there's a mighty good differential between the mainline pressure and the pressure coming from the corner spheres due to them being new and in-spec.

My view is that as all is good under power then don't worry.

One thing I'd do is check you have a reserve of pressure to operate the brakes a few time with the engine stopped. If you have then no worries.

Did you replace the anti-sink sphere recently?

[isisalar]

Thanks a lot Jim, I suspected that the larger capacity would be a benefit rather than a problem. Just did the bounce the boot test and it went hard at 23 seconds. Good to know this indicates the corners are in good order as they are the only spheres that haven't been recently changed. They're the grey Citroen ones and are about 3 yrs/ 30,000 miles old.
Not wanting to turn off the engine going down a hill I tested the brakes by putting it on high, turning off the engine and trying to hold it up on the brakes after putting it in low. Was able to hold the car up for about 20 secs and still apply a bit of pressure after 30 secs, so I guess that's ok then.
Something that has been puzzling me about this is:- Comparing a hydraulic Citroen to a 'normal' car, if the engine stops, are you better or worse off in the Citroen re braking?
Cheers
Paul

[Mandrake]

So long as your accumulator and anti-sink spheres are good you will have stored pressure in the accumulator sphere and anti-sink sphere (in theory enough for about 50 hard applications of the brakes) then you are better off - your brakes will work just as well as they would with the engine running, for much longer than you would need to safely come to a stop, while a vaccum servo system will run out of assist fairly quickly.

On the other hand if both your accumulator sphere and anti-sink sphere are flat/punctured then you will pretty much loose all brakes (except hand brake) immediately when the engine dies or accessory belt snaps on an anti-sink model. Hence the importance to making sure those two spheres are not overlooked.

Also you have a pressure warning light which will come on on the dashboard if the system pressure is below 100 bars giving you ample warning the brakes might have a problem BEFORE you need them. I'm not sure whether vacuum servo systems have any sort of warning system if a fault is detected...

[CitroJim]

I'm not sure whether vacuum servo systems have any sort of warning system if a fault is detected...

Not so far as I know except 'Blimey, that pedal took a bit of pushing...'

[isisalar]

Once upon a time I had the dubious pleasure of driving a Saab as a company car for a while, an old L reg from memory. The brakes suddenly became very heavy and ineffective, the pedal feeling a bit like a housebrick, with a brake warning light on the dash. This completely foxed the service department until the manager did some research. As a new 'safety feature' when the pad wear indicator wire wore through, the servo was disconnected! A new set of pads and all was fine.
I can confirm that servo brakes do work without assistance but it's not much fun.
Just one of the things that put me off Saabs for life.
Cheers
Paul