To Sink or not To Sink

[cc101]

Hi all, just a quick thanks to all that have helped, slowly solving the issues.

Anyone have any thoughts on this one (1994 TD LX Sinker) before I changed the spheres the car car would sink pretty quickly (front & back) after switched off, say an hour or 2. Changed all four corner spheres yesterday and the car now sinks at the front like it used to but the rear will stay normal for ages, will sink over night though! Any ideas why it now does this!? (no anti-sink sphere on this car).

Cheers all.

[Xantianut]

Ay up, cc101!

Try lubricating the rear legs and height corrector. They do seize sometimes.

[cc101]

Cheers, I have lubed up the height corrector and arms, was just interested to why it's not sinking like it Sid before changing the spheres!

[Mandrake]

Let me get this straight, you're complaining that the suspension takes longer to sink than it did before you changed the spheres ? Thats a good thing, not a bad thing.

The only "bad" thing that might cause the rear to stay up unusually long on a sinker is if the rear arm bearings were shot, but if you can push the rear suspension down smoothly without it creaking or feeling like it has a lot of drag it won't be that. (Besides, it wasn't doing it before you changed the spheres)

The truth is the leakage rates of the suspension in a Citroen can vary dramatically for no good reason at all - on older models that don't have anti-sink the sinking rate can vary dramatically from one car to another. New spheres that are well gassed generally cause the car to sink slower than old spheres that are nearly flat or punctured, so its probably just the new spheres that have made the difference.

Back in the days of the GS/CX it was normal for the suspension to go down at the front first (typically in 30 minutes to an hour) then the rear could take as much as 6 hours to go down. The BX and early Xantia's usually go down at the rear before the front, but not always.

As long as the ride is good, the right height is adjusting itself correctly, and the rear suspension moves smoothly and easily when you push on it, a longer sinking time is nothing to worry about.

(You'll probably find the sinking time comes back to normal after a few days/weeks anyway)

[cc101]

Thanks Simon, no complaints was just interested to have an understanding if why it did it, most old Citroens you see sink at the rear first, so was just wondering why the front drops first now.

Cheers again.

[citroenxm]

Just for your information an "anti sink sphere" is just NOT that.. the sphere has nothing to do with the sinking or not, its a rear brake reserve. the only thing that controls anti sinking on an anti sink car is a mechanical 5 way valve on early models replaced by a 4 way one on later cars.

A lot of people think the sphere is the anti sink control.. its not.. there isn't one at the front . Only the pressure regulator..

there could be a higher internal leak in one of the front struts allowing the front to drop quicker then the rear....

[cc101]

Thanks for the replys, how would one go about tracing an internal strut leak?

Cheers.

[Mandrake]

You'll be chasing your tail looking for leaks in the front struts - 1 to 2 hours for the front to sink on a sinker is perfectly normal...in fact 2 hours would be considered very good, especially at the age they are now with natural wear and tear.

The major source of leakage that causes normal sinking in sinker models is the natural leakage of the height correctors, which are purposely designed without any internal seals. The anti-sink system in later models is just a special low leakage multiway valve which (in simple terms) isolates the height corrector from the suspension struts when the car is parked thus blocking that source of leakage. The struts themselves have extremely low leakage compared to a height corrector, if not an anti-sink model wouldn't stay up for days...

[cc101]

Thanks for the information Simon, the front sinks within about 10 to 15 minutes when switched off, not down to the stops but a fair bit!

[Mandrake]

Hmm 10-15 minutes is a bit fast. How long does it take to sink to the stops though ?

[cc101]

Hi, it'll take a good 7 hours plus to fully sink, cheers.

[citronut]

as you get out of the car it will raise slightly then settle back to normal night/level

so what year/spec is this car,

[cc101]

Hi Malcolm, it's a 1.9 TD LX 1994 Sinker, just 5 spheres, 90k on the clock. It had a new FDV regulator and hydraulic pump fitted about 3 years ago.

Cheers.