PAS or not!

[ollie]

Following from the PAS question we had a while back I felt I ought to do something about my own!

Well the upshot is, changing the Flow diverter for a spare just made no difference! still intermittent esp when cold.

So today I treated the beasty to a new Accum as others have tried, (and cos its 4 years old anyway) changed the LHM cos it was due this years anyway.... well again this has brought up a new result - it took me about 1/2 hr to regain hydraulic pressure !

- the pump wouldn't pull at all, not even trickling through direct filling from a funnel. Got bored so took it for a no suspension blast after about 5 minutes of enthusiatic wiggling and G forces the light went out!!!
Pas is now nearly normal.
Now this cars has never had this slow bleeding before so I can only assume its the usaul reason of - a dodgy Flow diverter!!! woopee, I wasted all that time to get another duff one!!

Anyway I have about 5 orther spares so Ill order some more seals and spend a weekend trying them all in turn! wish me luck

[Mike E (uk)]

Are you sure the pump is OK?

Your story reads just like mine.....

I had intermittant PAS which was finally cured with a new HP pump, after a new FDV was fitted.

Apparently, the PAS circuit uses a large volume of fluid, while the rest of the car hydraulic systems use only the pressure. So the 1st symptoms of a worn out pump is the steering going heavy from time to time.

(The accumulator helps maintain a constant pressure, like a smoothing capacitor in a power supply,but no flow volume.)

This happened mostly when the engine was cold, worst on cold days. (Thicker LHM?)

The 1st pump I fitted was an old one, took ages to prime, and gave the same PAS problem.

Got a new/recon pump from Pliades and it primed very quickly and the problem went away.

YIPPEE Job finally done.

[Vanny]

Its a flow distributer, it doesn't take flow from one place to another, but makes sure that the suspension system get pressure before the PAS (pretty much exactly the same as the 'security valve'), which is why is you have a weak pump or a dodgy accumulator they give problems with the PAS but now where else!

So at a basic level faults with PAS can be atributed to;
weak HP pump
flat accumulator
malfunctioning FD
leaking pinion valve (which makes a terrible hiss and is VERY obvious)
high pressure demands in the rest of the system (ie flat spheres, assuming fluid isn't gushing out!)


In answer to the poll i chose, yes they are the spawn of satan, simple reason being that i dont have an FD and more productively i haven't had any problems with the PAS (except user error!). However removing the FD isn't the 100% solution, i also have the Xantia pump on mine which other than having a twin output, also has a higher pressure. When there is a purge of pressure (say through my flat rear spheres, one of which is flatter than the other) the surplus pressure in the very good condition pump deal happily with the loss so no problems!

The effects of a weak pump are also affected by the condition of your LHM, when it goes in its reasonably gloopy especially compared to what comes out, so new LHM can often mean a pump has difficulty sucking up (though i dont think this has anything to do with your problem Ollie) while total dead lhm cant be sucked up fast enough to fullfill the system requirements. A contact in total reckons that LHM starts to become less efficient after only 6000 miles (refer to manufacturer recomendations for fluid changes), and further more i know of a guy who has run his GSA on Hydroflush for in excess of 34,000 miles without a single suspension fault, i get the impression that hydraflush is nothing more than aviation hydraulic fluid (and a bit more advanced).

So its all swings and round abouts in the magical world of hp suspension!

[jayw]

I've had the same problem since the cold weather started on one of mine.

Was planning to change the LHM to hopefully sort it but now i'm not so convinced.

How difficult is it to chance to a manual rack as i have one in the garage doing nowt?

[AlanS]

Over here, we often wonder about all the hydraulic strife such as this you guys seem to get with your cars and I've often thought that perhaps there may be a weather factor that's never allowed for.
The fact you get snow and rain over there and we seem to see little if any of either is what I mean.
I've only ever had strife with one car as regards strange hydraulic performance and that was on a car imported from the UK.
In that case, I took the p/r and f/d and washed them externally, then on the suggestion of Neil (CGAT - the guy with the immacukate CX Turbo) to someone on one of the lists, I tossed the pair of them into a container of petrol and blew them through with compressed air as well as seating the balls inside the pressure regulator. I was particularly careful that I had all the filters clean and I then did a total refill of fresh LHM and totally bled the system
The LHM was then religiously changed from then on and 70K miles later, it's still as good as new, so might be worthy of consideration.
The variety of belt sizes offered I feel can also be a roblem as is the tightening of balljoints, but my suspicion is that moisture contaminates these systems and causes ongoing problems.


Alan S

[ollie]

Well, might try the petrol trick as I've nowt to loose, maybe with a shot of redex in it too! plenty of the things to try it on as well!

Hope its not the pump as its only 6 months old from the great GSF, perhaps I should get a pressure guage on it, don't think its that though as no amount of citroebics can bring the low pressure warning light on!
and it runs for about 40 seconds between short sphere recharge clicks. which by any BX standards is pretty good!

Incidentally pinion valves can fail without noise, they just do random things and pull to one side, which I've had before, and is VERY unnerving!

Ollie