New member continuos hissing TZD

kole24 · Post by **kole24** » Fri Jun 06, 2008 8:55 am

Hello guys, first to thank you for great info database. After several months of watching and learnig, I have to confront you with my problem. It is identicaly same as the one that member Dumbtime had here [/url]http://www.bxclub.co.uk/forum/viewtopic ... inking[url] . Becouse I havent seen happy end, I assume that he havent fixed it. BTW my car is 1991 TZD, changed HG (with your help

), and now I am going thruogh hidraulics, to solve continuos hiss, wich is driving me mad.

PS
sorry about my bad English, I am from Serbia[/url]

MULLEY · Post by **MULLEY** » Fri Jun 06, 2008 1:34 pm

Welcome,

have you tried changing the accumulator sphere?

mnde · Post by **mnde** » Fri Jun 06, 2008 2:02 pm

Mine has exactly the same hissing problem. Changing the dead accumulator sphere for a brand new one has improved it, but not cured it. So I think that the HP pump is a bit tired. When idling there is this hiss that often continues for a long time, especially when cold, and only raising the revs a bit "encourages" it to reach cut-out. Also, at idle speed the car is very slow to rise from low to high position, even though the LHM is bright and clean.

Sound familiar, kole24?

Mark.

DLM · Post by **DLM** » Fri Jun 06, 2008 5:47 pm

Without referring to the previous thread (my library internet session's about to run out) I'd think along the lines of:

(i)weak or internally cracked pump - is there any knocking from the pump

(ii) pinholes/splits/deterioration in reservoir-to-pump hose (air in lhm returned to reservoir). Wetten pipe gently with lhm and watch for suckage.

(iii) PR cut-in at incorrect pressure (reseat the PR ball-bearing behind accumulator sphere using a suitable drift).

(iv) Possibly (I've only just thought of this in reference to what happened with another car) de-aerate the PR by loosening pressure at the 12mm bolt and running engine in this state for 30sec or so before retightening - car must already be at lowest height.

(v) Examine return pipe volumes, to see if any component or component group has gone hydraulic open-circuit (lhm return almost as fast as it's supplied).

kole24 · Post by **kole24** » Mon Jun 09, 2008 6:53 am

Thanks for your replies.
@DLM
(i) No knocking from the pump
(ii) I dont know, will try to change the whole hose
(iii) I suspect that this is the problem, already reseat the ball-bearing without result, but will change both ball-bearings and reseat them both.
(iv) Will try that today afternoon
(v) There is almost none return of LHM to the four small return pipes with engine running, only the big one have some amount of return with engine stopped.
@mnde
exactly the same, it stops hissing only when turning the steering wheel.
@MULLEY
Already tried that, but thanks.

kole24 · Post by **kole24** » Mon Jun 09, 2008 7:07 am

Also have to tell you that if I open reservoir for filters cleaning, car stops sinking for couple of days and then starts sinking again. Main thing is that FILTERS ARE CLEAN, and even if I dont clean them, but only open the reservoir car improve behavior. I think that I am going mad. I am familiar with mechanics and hidraulics but I cant figure it out.

jeremy · Post by **jeremy** » Mon Jun 09, 2008 7:35 am

What is the condition of the main pump feed hose that runs from the reservoir to the pump?

It is vitally important that this hose is in good condition and SEALS well at both ends. Its common for the reservoir end top get ragged when it has been disturbed and the rest of the pipe has been known to get porous. When this happens it lets air in but does not let LHM out.

This hose can temporarily be replaced with a clean but of garden hose for diagnostic purposes. (Make sure it isn't sucked flat)

What happens is that the valves seal for LHM but act as filters for air and let it past. It may be possible to see air bubbles in the reservoir - there tend to be some during normal operation. Green milky LHM is another symptom (Looks like milk but green)

New LHM often causes a significant improvement but it doesn't last.

My own TD tends to hiss form the regulator rather than make a sharp click - and has done so for years. It all functions properly if a bit slowly at times - but recently I had to put in about 3 litres of LHM after a major leak - and the thing rose within 5 seconds from the low position and stayed raised overnight - but was back to normal after 10 days unfortunately.

tom · Post by **tom** » Mon Jun 09, 2008 7:41 pm

Your Doseur has worn out. See the sticky "Mysterious fast tick times" for an explanation.

kole24 · Post by **kole24** » Tue Jun 10, 2008 6:25 am

Yesterday I have changed the main feed hose, but no effect. I was suspecting the doseur, but I can't explain what happens when I open the reservoir. Normally, when doseur is gone, the rear end sinks rapidly ( this is my case) but when I open the reservoir, it stays up for three days.

Aerodynamica · Post by **Aerodynamica** » Tue Jun 10, 2008 12:04 pm

Hi, I just joined you folks! but I wanted to add something about this penomenon.

This subject crops up often over the years on French car Forum and others, my take on this is that it is actually a totally normal characteristic of the system fitted to cars with a flow distributor valve (BX with PAS, Mk.1 Xantias up until 1995, Mk.1 and Mk 1.5 XMs) - three models.

I first noticed it when these models were more abundant in the early 90s, I'd hear this noise coming from them stopped in traffic when I was walking to school. These cars were new or couple of years old. Then I persuaded my old man to choose a Xantia and then our Mk. 1 Xantia would make the intermittent hissing when running. Years later the accumulator went and the hissing changed to a little 'chirp' every 2 seconds ( seemed directly connected to the rapid regulator clicking) upon replacing the accumulator the hissing returned and the steering feel improved.

Some owners see this hissing sound as a fault - I always thought it was cool and would always identify a nearby Xm or something by this. The earliest memory of it though was at a Citroen dealer in the late 80s, we were there to get some seatbelts fitted to the family 2CV and we got a demo of a new BX. When it was started and rose up there was that audible, occasional and at times quite long hissing sound of 'some hydraulic mechanism' in there. To this day I'm certain it's not a fault at all especially where there are no other symptoms like sloppy steering or mega slow suspension.

I'd agree it shouldn't be constant but intermittent. Only last weekend I saw an XM in traffic here making the loudest, longest hiss (seemed never to stop) and I don't think that's right. So don't write it off as a fault especially where there are no other symptoms o faults. I think the hissing is a pressure balancing between the outflow of the pressure regulator's 'dump' pipe through the FDV depending on demand of the steering. The hissing may even stop breifly while the suspension is moving up or the steering is turned only to start again when all is stationary.

That's my longest first post ever

tom · Post by **tom** » Tue Jun 10, 2008 9:25 pm

The rear height corrector often has a great deal of influence on the rate at which the back end sinks. I have known many BXs that stay up for hours but still have worn out doseurs.

Vanny · Post by **Vanny** » Wed Jun 11, 2008 1:03 am

taken many doseurs apart yet TOM?