Xantia pulse sensation through seats

Kowalski · Post by **Kowalski** » 09 Jul 2004, 19:09

LHM should be bright neon green, any yellowing is a sign that its past time to change your LHM.

jeremy · Post by **jeremy** » 09 Jul 2004, 19:41

The answer to your question is that a weak pump is -well - weak. If yours was weak I would expect the PAS not to work properly - perhaps going heavy when the steeringwheel was turned fast. I would also expect the car to rise very slowly and struggle. Having said that I gather that twin outlet xantias are'nt very spritely when new (when raising the suspension of course)
I originally suggested spheres as I could not think of anything else that could cause a rythmic pulse. I still can't and although I've no actual experience with Xantias I've never seen anyone else complain of such problems.
I suppose one way of determining if the pulse is related to the hydraulics would be to determine its frequency. If the pulses are counted over say a minute, the engine revs noted and then the 2 pulleys driving the pump measure it should be possible to establish pump speed at certain engine revs and see if there is any relationship. I assume the 2 suspension cylinders are 180 degrees apart in operation in which case I would expect 2 pulses per pump rev. The pump probably doesn't rotate at engine speed but a bit above so its necessary to work out its speed.
As you've probably gathered I like to know definitely what is at fault before I start spending money!
jeremy

uhn113x · Post by **uhn113x** » 09 Jul 2004, 22:09

Hi HR
<blockquote id="quote">quote:<hr height="1" noshade id="quote">Yes Uhn113x, the name was pinched to reflect my tendency to endlessly try to fix anything rather than throw it. I’ve had my zx for 6 years, fixing control stalks door locks etc <hr height="1" noshade id="quote"></blockquote id="quote">
Yes - The late William Heath Robinson (the cartoonist and illustrator) is one of my heroes. If you ever get the chance, buy or read 'How to be a Motorist' [:D][:D]
Back to your LHM, it should be as new, otherwise it needs changing, and the system flushing, and filters in reservoir cleaning. How is the car now? Comparison with a ZX suspension is slightly biased as the ZX rides better than most things sprung with steel.

heath robinson · Post by **heath robinson** » 11 Jul 2004, 15:00

I like your take on accurate diagnosis Jeremy, it makes sense. The mathematical challenge forces me back to a bit of guess work though. I’m certain the problem is hydraulic, as it is the most immediate connection between the engine speed and the vibration/pulse. I guess to be sure what I would do is to run the engine with the pump drive belt off to isolate hydraulic causation? The only current doubt I have is that I understand that when the car is on its lowest setting it is on its bump stops and not suspended by hydraulics; in which case why would a hydraulic symptom still present? I’m almost sure the back centre sphere has had it, as the car rear does sink overnight. Will change just to see at some point, though seems from the forum that this will make no difference as serves principally as a rear brake reserve rather than to further cushion the suspension?
I’ll look out for the book ukn. The filters looked fine, couple of bits of black only. May hold back putting the flush in as I have some very long journeys ahead; having read around the forum, concerned that I might dislodge muck and up with a bigger problem while on my travels. Or are the risks negligible? would you trust the reliability of your car any less over a couple of thousand miles with flush in? I realise this is going a bit over the flush limit, but it’s about fitting in maintenance work on the car.
Given the xantia does enough for me car wise, and I imagine I will always opt for sub £2000 cars as I never want to worry too much about a car and its depreciation, I will probably look out for a spares/repair xantia to stock up with parts. I’m intrigued by the challenge of this bizarre way of holding a car up and making it stop. 4 years on I’m still holding off on the option to have a lease car from Ford through work; gluten for punishment?
Today I have my zx box to; let’s hope the radiator survives.
Thanks again
regards

nick · Post by **nick** » 11 Jul 2004, 15:34

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by heath robinson

I’m certain the problem is hydraulic, as it is the most immediate connection between the engine speed and the vibration/pulse. I guess to be sure what I would do is to run the engine with the pump drive belt off to isolate hydraulic causation?
<hr height="1" noshade id="quote"></blockquote id="quote">
That would certainly prove whether the vibration is caused by the hydraulics or not. If it is, removing the belt should completely stop it.
Nick

heath robinson · Post by **heath robinson** » 24 Sep 2004, 15:51

Pulse on tick over has hydraulic causation. No pulse when engine run with aux belt off.
6 new spheres, new filter, cleaned reservoir and running flushing lhm: the pulse goes on. the pulse goes at just over 1000 rpm; it smoothes out. It is also less noticeable when facing uphill on a steep gradient, therefore weight transfer to the rear of the car.
I have also noticed that when left overnight, I sometimes have no brakes before the engine is started, does this suggest excessive leak back from worn suspension units, thus exhausting accumulator reserve? Could this be the pulse?
Are there any rear axle bushes/mountings that could wear, thus produce the pulse? Can’t seen any indication of rear arm bearing wear as a possible cause. I imagine there would be a metallic knock in any event? No noise with the pulse.
Thanks again for any ideas
regards

mseymour · Post by **mseymour** » 24 Sep 2004, 18:26

<blockquote id="quote">quote:<hr height="1" noshade id="quote">I have also noticed that when left overnight, I sometimes have no brakes before the engine is started, does this suggest excessive leak back from worn suspension units, thus exhausting accumulator reserve? Could this be the pulse?<hr height="1" noshade id="quote"></blockquote id="quote">
Yes, I suspect it could. If you've got all new spheres and cleaned up the LHM then the ride should be good. If it isn't then you can start to look at things like the rear arm bearings, but these being knackered wouldn't result in any kind of pulsing.
I've asked for advice here on how to diagnose leaking struts, but nobody seems to know. The fronts are quite easy. There's a rubber leakoff pipe at the base of the strut. This takes fluid back to the reservoir. This pushes onto a metal pipe fixed to the front subframe. Pull it off and see what's coming through. If there's a few drips, that's fine. However if there's loads of LHM pouring out the strut is leaking internally and must be replaced.
I don't know how to test the rear struts, I guess there same procedure, but I don't know where the LHM return pipes are and if they're easily removeable.
At a guess you could check how many pipes are returning lots of LHM to the reservoir. On a Xantia with the 5+2 pump I'm guessing it's 2. One from the pressure regulator and one from the power steering. Other pipes returning lots of LHM indicate a failure.

heath robinson · Post by **heath robinson** » 25 Sep 2004, 20:26

Thanks
I imagine, given the principle, the rear must have a similar leak back circuit. When I took the lhm tank off to clean, I noticed further down from the tank some of the pipes feed into one another; these may be rear returns?
‘pulse’ may be an understatement. At worst (750 rpm), it is a less severe experience than sitting in an old truck cab and being lightly bounced by the truck engine. I think I need to get under on ramps to see what is moving; either the rear struts reflecting pulsating variations in pressure or not holding the pressure due to leak back, or whole suspension unit movement which emphasises pump pulsations which would otherwise be undetectable. Are there any rubber mountings that could wear and so give exaggeration?
regards

johntaylor · Post by **johntaylor** » 26 Sep 2004, 04:38

If you want to have a better understanding and correct advice please look at the web site on www.tramontana.co.hu/ or type in 'citroen do-it yourself' on google to se the same web site. Please note the warnings on safety when working underneath this system....it can squash you! The anti sink valve was on later models and is there to support the system from sinking when stationery! It does not have any role when the system is operative......when the engine is running.

heath robinson · Post by **heath robinson** » 26 Sep 2004, 16:48

hi john
thanks for the site. are you able to say what translation is required? interesting to hear the info on the valve, thanks