Good doseur but still sinking - help!

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Good doseur but still sinking - help!

Post by Pluto » Fri Oct 14, 2016 11:11 am

Hi all

I recently fitted a good replacement brake valve to my tdg estate as the back end was starting to sink quite quickly after the engine was shut off (it used to stay up for about 12hours). I could find no visible leaks anywhere and all 5 spheres were replaced less than 5k miles ago so I assumed the doseur was the culprit!
It was supplied by pleides so it should be a good one!

The problem is that the car still sinks at the rear. If I'm parked up for 10-15 min's it will drop by a couple of inch's, after about 1hr 45mins the back end is on the floor. It does stay up longer in the higher settings (maybe an extra hour). Is this normal/OK?

If not, what components should I be looking at? I have seen new height correctors for sale but don't want to splash out over £100 if it's not needed! Any advice would be much appreciated.

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Re: Good doseur but still sinking - help!

Post by rutter123 » Fri Oct 14, 2016 11:36 am

Rear height corrector leaking back internally i suspect. Both mine drop at the rear overnight never really caused any probs. The doseur valve is more applicable to the braking system not necessarily the height correction.
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Re: Good doseur but still sinking - help!

Post by JayW » Fri Oct 14, 2016 1:05 pm

The doseur is only relevant it the rear drops while the footbrake is pressed (such as waiting at traffic lights), so your original diagnosis would have been incorrect.

Either height corrector as suggested, or more likely one/both of the rear cylinders leaking by. Pull off the return lines and look for lhm leaking past. The normal amount is insignificant.
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Re: Good doseur but still sinking - help!

Post by Pluto » Fri Oct 14, 2016 5:49 pm

Thanks for the reply's. Much appreciated!
I'll check the return lines and see what's occurring

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Re: Good doseur but still sinking - help!

Post by senmathal » Fri Oct 14, 2016 7:57 pm

The doseur is relevant even if you don´t press the brake pedal and has to do with the anti dive function. This is a well known and common problem. It can be a little bit tricky to overhaul the doseur. Some times a cleaning works and sometimes not. The sinking when you press the pedal is the anti dive function and is as i should be. But of course it can be other reason for your cars sinking. The only specification for sinking time from Citroen was that the car should be up when you drive it. But it is not so funny with a fast sinking car.

/Mats

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Re: Good doseur but still sinking - help!

Post by themildbunch » Tue Oct 18, 2016 11:42 am

All my BX's sink over time - I've only had one stay up more than 5 - 6 hours after changing a component on the system or changing fluid and needing the bleed the system. Several days later though they'll go back to sinking gradually at the rear after a few hours.

It's never bothered me and has been like this for as long as I've owned BX's...

I think the components in the system will just gradually wear over time so the sinking is progressive - I'd only worry about it when things start happening much more quickly..
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Re: Good doseur but still sinking - help!

Post by RobC » Tue Oct 18, 2016 11:48 am

I've got pretty new front struts on mine and it still sinks at the front after a few hours. The rubber return pipes from the front struts are always bone dry though, so I wonder where the LHM goes - is there another return from the front suspension I don't know about?
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Re: Good doseur but still sinking - help!

Post by Pluto » Tue Oct 18, 2016 6:43 pm

Thanks for the input, it makes me feel a bit better knowing it's a fairly common thing. The front will stay up for a couple of days before it finally drops and the rear used to stay up for around 12 hours, it's only in the past few months it's started sinking considerably faster which made me think something on the car had started to fail. I used the car again today and the back had totally sunk after an hour. But if this is 'normal' then I'll stop worrying so much! I just would have assumed that gradual wear and tear on the hydraulic components wouldn't result in such a rapid change in 'sink rate'. I'll keep a close eye!

I will pull the return lines off the rear cylinders to see what's going on when I get some free time and it's not hammering down with rain.

Meanwhile, if anyone knows if new rear cylinders are available for estates anywhere (or height correctors) then please let me know!

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Re: Good doseur but still sinking - help!

Post by Kitch » Wed Oct 19, 2016 9:43 am

BAH is on the deck all round within 4hrs!

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Re: Good doseur but still sinking - help!

Post by Way2go » Wed Oct 19, 2016 5:22 pm

It's quite usual for the car to sink after a while via the returns from the height correctors.

A useful tip when you get a ruptured octopus is to put the car into "Intermediate" and you can continue a possible long journey home with minimal loss of LHM (especially when stopping for a while!). Consequently putting the car into "intermediate" when parked is likely to prolong the time before sinking even on a BX with a good octopus.

Use the above as a test rather than as a routine to observe. :)
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Re: Good doseur but still sinking - help!

Post by senmathal » Thu Oct 20, 2016 10:01 pm

Rapid change in sink rate often depends on the brake douser. Dirt in the LHM make that the piston don´t find the exactly place and some oil will leak through it. Sometimes Hydraurincage cleaning liquid can help but sometimes not. The pistons and cylinders in the hydraulik valves system don´t usually wears so fast.

/Mats

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Re: Good doseur but still sinking - help!

Post by Jaba » Thu Oct 27, 2016 1:35 pm

The other way of looking at this is the front takes a long time to sink. When this is the case with stiff front struts then it can be easy to diagnose a rear end that sinks too quickly instead of a front end that stays up too long !
On my two BXs the front and rear sink at about the same rate and I keep the front struts well lubed.
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Re: Good doseur but still sinking - help!

Post by kiwi » Sat Nov 05, 2016 6:53 am

Following this with interest! As that troublesome BX Estate I have got has now decided to drop at the rear quite quickly when parked. So much so it was noticed when I went into the servo when the guy behind the counter asked what I had in the boot that was so heavy.....got me for while as it was a Light Washing Machine!!! Adding 40 litres of fuel surely not that much wait either...lol.

My pump still seems to be over working as well.
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