Tip: Hydraulic pump reluctant to pump after fluid change

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white exec
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Location: Sayalonga, Malaga
My Cars: 1992 BX19D Millesime
- LHD, NA, AC, RP_5800
1996 XM 2.5TD Exclusive
x 53

Tip: Hydraulic pump reluctant to pump after fluid change

Post by white exec »

:idea:
Forgot to mention this...

Twice, over recent months, the hydraulic reservoir has been syringe-emptied to refill it - first with Hydraurincage, then later with regular LHM.

Both times, although the pump had not been emptied (or engine started), on restarting the pump just wouldn't shift fluid, so presumably air-locked.

Found a quick remedy the second time: with engine running, operated the steering from lock to lock a couple of times, and up the pressure came up quite quickly. The steering places a very large demand on fluid flow, seemingly enough to get fluid moving through the pump. This worked on both occasions.
Chris

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David
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Re: Tip: Hydraulic pump reluctant to pump after fluid change

Post by David »

There's a sealed plastic housing inside the LHM tank, below the feed pipe's union which allows the pump to suck oil from the bottom of the tank. When you syphon all the oil out, then it will draw the oil out of this said housing too, which will be causing your air locks. There's a filter inside the housing too & another one on the return, so if you haven't done already, it'd be a good idea to remove the whole LHM tank & clean out these filters.

I wish that I was so lucky when my car's pump gets air locked. On mine, I have to remove the oil feed pipe from the top of the pump, put a funnel in the end of the pipe, fill the hose back to the LHM tank with oil & then quickly reconnect the said hose to the hydraulic pump before all the oil runs out of the pipe & back into the tank. Then start the engine & run it at around 2000rpm until the hydraulics pressurise.

The joys of temperamental Citroen hydraulics!
1992 Citroën BX 1.9 Diesel Meteor 4x4 - The Project.

1992 Citroën BX 1.9 TXD (with GTI engine; Mulleys old car) - Parts car.

2004 Citroën Xsara Desire. (Now gone).

2016 Ford Focus Zetec - Daily Driver. (Absolute bone shaker).

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white exec
BXpert
Posts: 505
Joined: Sat Sep 12, 2020 4:04 pm
Location: Sayalonga, Malaga
My Cars: 1992 BX19D Millesime
- LHD, NA, AC, RP_5800
1996 XM 2.5TD Exclusive
x 53

Re: Tip: Hydraulic pump reluctant to pump after fluid change

Post by white exec »

Originally (back in October) did the funnel into the suction hose, twice, and it was (surprisingly) not successful - the pump still wouldn't deliver.
Resorted to well-filling the reservoir, but still no go until I turned the steering wheel.
Concluded this created a significant delivery for the pump (creating a fluid 'exit'), and this got things moving.
All this had taken a good half hour of messing about.

This time round, as soon as the pump wouldn't, I straightway turned the wheel, and the problem cleared.

Re: the filters, I don't think the surround to the intake filter is 'sealed', although the filter should fit fairly snugly into place. Similarly with the conical output filter. Fluid is meant to enter the first filter, leave it, and travel across the tank to the exit one. Apart from trapping dirt, we've found that an important function of the fine nylon mesh is to break up bubbles which get created/returned to the tank, to prevent them from getting re-circulated into the hydraulics.

Agree with what you say. though, about the risk of air initially getting into the pump after the tank has been drained, then refilled, likely when the tank end of the suction dip-tube empties itself.
Chris