Frequency of hydraulic pump 'clicks'

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alf
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Frequency of hydraulic pump 'clicks'

Postby alf » 23 Jan 2002, 10:19

When buying second hand Xantia TD, whats the click frequency (technical term) one be looking for and what rate should sound warning bells?
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JohnD
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Postby JohnD » 24 Jan 2002, 00:45

Hi Alf - If it clicks once every half to one minute, you can take it that the accumulator is OK. As it gets near to once every few seconds, be ready to replace it.
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alf
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Postby alf » 24 Jan 2002, 05:22

Thanks John D, Could you clarify a point for me? Is it the pump that clicks or the accumulator sphere. Pump = loadsamoney, Accumulator sphere = not too bad.
TVM
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henrysheil
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Postby henrysheil » 24 Jan 2002, 12:10

Hi Alf,
The sphere is a pressure vessel with a bladder inside, the bladder (like a balloon)being pressurised with Nitrogen gas. The LHM goes in the end and "squeezes" the bladder from the outside. It can't make any clicking noises.
The pump does the clicking, but it is turned on and off by the regulator which is where the sphere screws into. The regulator's commands to the pump to switch on or off are determined by the pressure in the system, and the rate of pressure loss/drop inside the system is governed by the precharge in the accumulator. When its precharge is low its ability to help top up hydraulic pressure in the system is reduced, so the pressure drops faster, so the pump has to cycle on and off more often.
Geddit? It's all very logical.
Henry
<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>
Thanks John D, Could you clarify a point for me? Is it the pump that clicks or the accumulator sphere. Pump = loadsamoney, Accumulator sphere = not too bad.
TVM

<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
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alf
Posts: 21
Joined: 13 Aug 2001, 02:46
Location: United Kingdom
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Postby alf » 24 Jan 2002, 23:47

Thanks Henry for an understandable explanation without the technobabble. As I understand it if its clicking frequently try changing the sphere before you start spending any serious money.
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JohnD
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x 2

Postby JohnD » 25 Jan 2002, 00:53

Hi Alf - 99 times out of 100 the reason for the frequent clicking is the flatness of the accumulator sphere. Normally the pump is a long lasting item (providing LHM has been changed at recommended intervals), whereas the spheres last around three to four years.
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