Xantia Exclusive HDI 110 leaking LHM from pipe behind engine

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davoxx
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Re: Xantia Exclusive HDI 110 leaking LHM from pipe behind engine

Post by davoxx » 06 Oct 2018, 19:34

i never knew about the compression joint not being safe, please ignore my comment about using them.

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white exec
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Re: Xantia Exclusive HDI 110 leaking LHM from pipe behind engine

Post by white exec » 06 Oct 2018, 19:39

No problem. Simply a matter of the pressures involved.
Worth leaving the post there, as it is a useful reminder.

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CitroenCrazy
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Re: Xantia Exclusive HDI 110 leaking LHM from pipe behind engine

Post by CitroenCrazy » 06 Oct 2018, 21:10

Just out of curiosity, I looked at the question of whether compression fittings are suitable for Citroen hydrauulics or not. I'm not sure it's as clear-cut as suggested earlier.

I've attached an excerpt from the specification published by Wade, a UK compression fitting manufacturer. They state that the maximum operating pressure is 210 bar.
Now, the obvious caveat is the bottom line - please ensure the tube used is suitable....

One thing I noticed is that Wade use parallel copper olives which may give a better grip than the more usual shaped brass ones.

Equally, the entire hydraulic system on a Xantia is not exposed to the maximum pressure achieved at the accumulator. A good example is the power steering. I've tried and so far failed to find a specification that sets out the peak pressure in this circuit, but the pump has a high pressure (2 piston) and a low pressure (six piston) side, so my guess is it operates at less than 100 bar, probably a lot less.

I haven't done it yet, but the next time I need to replace a rotten section of PAS pipe on a Xantia, I don't think I'd worry too much about using a compression fitting.
I probably wouldn't try it on a brake or suspension line.
Attachments
Wade compression fittings.gif

pete the bus
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Re: Xantia Exclusive HDI 110 leaking LHM from pipe behind engine

Post by pete the bus » 06 Oct 2018, 21:50

As we're on the subject of different types of fittings do I need to use a LHM friendly type of pipe, be it metal or rubber, or as, in this case, it's not a high pressure line, will anything do?

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CitroenCrazy
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Re: Xantia Exclusive HDI 110 leaking LHM from pipe behind engine

Post by CitroenCrazy » 06 Oct 2018, 22:08

Any metal will be ok. In terms of flexible pipe, LHM is pretty benign stuff, so you should be ok with anything sold as fuel hose. Personally, I would avoid flexible plastic pipe; in my experience it goes hard and brittle in the end.

pete the bus
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Re: Xantia Exclusive HDI 110 leaking LHM from pipe behind engine

Post by pete the bus » 06 Oct 2018, 22:20

Thank you.
I shall double check that I've identified the right pipe and consider using a short length of fuel hose to replace the corroded metal section.

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white exec
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Re: Xantia Exclusive HDI 110 leaking LHM from pipe behind engine

Post by white exec » 06 Oct 2018, 22:39

CitroenCrazy wrote:
06 Oct 2018, 21:10
Now, the obvious caveat is the bottom line - please ensure the tube used is suitable....
Image
...and the remainder of the caution too: vibration-free, and temperatures up to 65°C.
Under-bonnet conditions regularly top that figure.

My understanding is that current MoT regulations prohibit the use of these fittings for high-pressure vehicle hydraulic lines, unless the olive involved is brazed or welded to the pipe, or an integral part of it. I can't quote chapter and verse on this, but someone here may be able to.

Do take your point about lesser pressures in some parts of the system.

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Re: Xantia Exclusive HDI 110 leaking LHM from pipe behind engine

Post by sparksie » 07 Oct 2018, 02:54

I doubt whether any normal compression fitting would withstand the heat and vibration at any pressure, never mind the suspension and braking system on a Xantia.
However, a proper flared end, where the "olive" is formed out of the end of the pipe itself, just like conventional braking systems, is a different matter. Fittings and flaring tools are available for the common pipe sizes, in both imperial and metric sizes. If joining pipes using a flare fitting, remember to support the fitting when finished. It will be heavier than a simple pipe and may resonate and cause premature metal fatigue failure.
I have two such joints on Cit, where a plastic clip failed and a brake pipe chafed through against the end of the gearbox.
No problem at test time, despite them being very conspicuous, viewed from below.

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white exec
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Re: Xantia Exclusive HDI 110 leaking LHM from pipe behind engine

Post by white exec » 07 Oct 2018, 07:29

As you say, flare fittings are what should be used for repairs, if not complete new pipes.
Original Citroen hydraulic joints included flares (eg on 10mm Hydractive piping, where the pipe couples with a valve or strut), or olive/bulge-and-rubber sleeve for the smaller pipes (6.35, 4.5, 3.5mm) where the bulge is formed from the steel pipe itself. These latter joints actually become more leak-resistant as pressure increases, and slippage of the pipe is impossible.

Compression joints (with ring olives) rely on the olive digging in to the pipe to achieve a non-slip seal. This works ok where the olive is harder than the pipe - eg a brass olive with a copper pipe - but does not work with standard compression fittings where the pipe is steel. All that happens here is that the (brass) olive will crush up and hold the pipe by friction, not a positive indented 'ridge'. As such, it is prone to losing its grip, as a result of varying heat and vibration, and the hydraulic pulsing that is inherent in these systems.