HP pump air leak affecting ride quality ?

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Mandrake
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HP pump air leak affecting ride quality ?

Post by Mandrake »

AndersDK wrote:Try do the Citaerobics (fully up & down) several times. If air (or gas) gets into the fluid side of the suspension, then it oddly feels very hard.
This will be vented by the citaerobics.
Anders, you're a genius :D

I've ripped this quote out of another thread and posted it here as I think it deserves a fresh thread.

Regular readers will know I've been chasing intermitant harsh ride on my Xantia for some time now, and all kinds of possibilities have been explored, and naturally the spheres are all in good condition and at normal pressures etc.

The symptoms are harsh ride over any sudden bumps such as manhole covers, potholes, corrogations, etc, and also sometimes the ride seems "unsettled" and "underdamped", especially at open road speeds. Furthermore the ride quality seems to vary on a day to day basis. :roll:

When I first got the car approx 9 months ago greasing the struts seemed to cure it, but in a couple of months the problem was back, and in subsequent attempts, the improvement has been even shorter lived to the point where the ride is back to noticably harsh even the same day, let alone the next day or a few weeks later.

Another thing which I had noticed is that after doing Citroerobics the ride is invariably improved very noticably, but is often harsh again within 20 minutes of driving, and certainly by the next day it is poor again.

Today I decided to look at the possibility of air getting into the hydraulics even though the car showed none of the classic symptoms of air in the system, and I wasn't convinced that air could really have that kind of effect on the ride. Anders comments prodded me into investigating the possibility again.

After peering into the tank with a torch and the engine idling I discovered to my surprise that there was quite vigourous bubbling inside the main filter, although there was no froth in the main part of the tank. After inspecting the pipe I found a crack near the clamp on the HP pump which opened wider when bending the pipe slightly. :shock: :shock:

I was a bit surprised as a few months ago I had replaced the clamp on the pump because it was loose, and I either didn't notice it then, or the crack didn't exist then.... :oops:

So I attempted to cut the pipe shorter and refit it, and discovered the hard way that the pipe has gone hard and rotten, and when I attempted to fit it back onto the pump the new end of the pipe literally tore off :shock: not very impressed to say the least, for an 8 year old pipe.

So I was forced to cut it even shorter and try more carefully to fit it, and this time I was successful. Because its too short now and because the material has partially disintegrated (heat ? age ?) I'll be getting a new pipe but this will do in the mean time.

Much to my disapointment it still seems to be bubbling slightly in the tank, but I decided to try it anyway, so I gave it a good bout of about 5 lots of Citrerobics and bled the regulator a few times for good measure, and went for a test drive.

WOW! The unsettled underdamped feeling was gone, and the stability at high speed was excellent. The ride, even though I still don't think it is quite up to standard for a Citroen has lost most of the harshness that it had before, and is drastically better.

I've seen this before though after doing Citreobics or strut greasing and usually the effect wears off in about 20 minutes of driving so I went for an hour long drive on a variety of city and country roads, and it showed no sign whatsoever of deteriorating. Of course the real test is what it is like a week or more from now...

So what can I conclude ? It seems as if a small air leak on the pump input has existed the whole time I've had the car - not enough to make the tank frothy, but enough to get air into the system gradually.

Because the anti-sink system keeps the car from depressurizing unless you're using the manual height lever, once air gets into the system, it wont self bleed (much) with normal day to day driving with small load changes like one person getting in and out.

This leak must have got progressively worse over the last few months, and was also probably somewhat intermitant, as the hose moved around.

I also now strongly suspect that a large part of the perceived benefit in ride from doing the strut greasing was in fact the Citrerobics that was part of the procedure - eg you have to raise the height to maximum to apply the grease/oil, then lower it to minimum to work it into the strut, and repeat a few times, and in the process you are bleeding any air from the system.

However with the pump leak still existing, air will get into the system again and accumulate in hours/days/weeks depending on how bad the leak is.

I also theorize that Hydractive 2 models are more prone to air bubbles affecting the ride quality because you have the long 10mm diameter pipes from the struts to the hydractive sphere to potentially get bubbles of air trapped in, and that would be the worst possible place for the air to be.

The lack of damping and the harsh ride are both easily explained by air bubbles - assume there was a significant pocket of air trapped in the pipes between strut tops and hydractive sphere, small body movements would cause the air bubble to compress and expand instead of forcing oil back and forth through the damping valves = no damping for small movements.

Meanwhile large sudden movements like potholes would cause the air bubble to be suddenly compressed and then cause a sudden jolt when the bubble is squashed down to almost non existant size due to the sudden pressure increase of a bump - the effect on the ride would be very much like worn balljoints in the suspension or rollbar links.

Will be interesting to see what happens to the remaining bubbling (and the ride) when I get the new pipe...

Regards,
Simon
Simon

1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
2016 Nissan Leaf Tekna 30kWh in White

2011 Peugeot Ion Full Electric in Silver
1977 G Special 1129cc LHD
1978 CX 2400
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1998 Xantia S2 3.0 V6 Auto Exclusive
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Post by Kowalski »

You've got a suprise coming when you see the price of that pipe from the Citroen dealer. ;)
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Mandrake
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Post by Mandrake »

Kowalski wrote:You've got a suprise coming when you see the price of that pipe from the Citroen dealer. ;)
Would you like to put a figure to that, or are you just trying to scare me :(

Regards,
Simon
Simon

1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
2016 Nissan Leaf Tekna 30kWh in White

2011 Peugeot Ion Full Electric in Silver
1977 G Special 1129cc LHD
1978 CX 2400
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Post by steviewonder7 »

Be interesting to know as I need to replace my HP pipe soon :(
1994 Xantia 1.9TD sx non anti sink.No aircon.Gone to the great scappy up above.

Now with Xsara Picasso 2.0 HDI (90 bhp)(03 plate) in 'Wicked Red'
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Post by Mandrake »

I presume that the original hose has all moulded bends as well ? (Or has mine just gone hard with age...:) )

Has anyone successfully replaced the entire length with "standard" flexible straight hose or are there too many tight or unsupported bends to follow this approach ?

PS I'm aware of the need for the pipe to be LHM resistant, and also that it needs thick walls to prevent collapse under vacuum.

Regards,
Simon
Simon

1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
2016 Nissan Leaf Tekna 30kWh in White

2011 Peugeot Ion Full Electric in Silver
1977 G Special 1129cc LHD
1978 CX 2400
1997 Xantia S1 2.0i Auto VSX
1998 Xantia S2 3.0 V6 Auto Exclusive
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