Cold weather affects Xantia Hydraulics?

reffro · Unread post by **reffro** » 08 Jan 2003, 14:51

Been particularly obvious during this cold snap that my Xantia (94 2.0i 8v VSX auto) has been affected. On start up the suspension is a bit slower to sort itself out, and the steering is a lot harder to turn (both ways not just one direction) also.
Unfortunately this morning the offside front caliper was binding on my disc. But given a a bit of heat after 1 mile of driving it freed itself. I'm sure this will be one off, well fingers crossed it is.
I realise that the cold weather should affect the fluid properties of the LHM but it is very noticeable the difference. Does anyone suffer these symptons, particularly the steering, or is there something I need to be looking at on my car? Just for the record I had the LHM drained and replaced along with a clean out of the reservoir and new filters, so I'm not worried about the condition of the LHM. The Levels are all OK, so maybe its just related to the cold weather.

tka · Unread post by **tka** » 08 Jan 2003, 15:22

I don't know how cold is there in England. Here have been -20...-30 celcius degs for two weeks. When I start my Xantia the steering is very heavy the first minutes. Also hydraulic pump needs more time to get the right pressure when it is cold. This is only when it is very cold and it is logical because the LHM fluid is mineral based (compare mineral engine oil to fully synthetic oil). If I remember right there was no problem when it was around 0 celcius degs or some minus degs. I have to wait warmer weather to check it out.
Tero
Tero

mbunting · Unread post by **mbunting** » 08 Jan 2003, 18:59

I have also noticed this effect.
Of course, having a slightly leaking pump ( looks like the actual pump ), does not help the pressure in the morning.
My handbrake thingy on the left caliper seized yesterday, plenty of WD40 and a claw-hammer soon sorted that out ! Presume all the salt and grit.

rory_perrett · Unread post by **rory_perrett** » 08 Jan 2003, 19:50

Same thing happens with BX's as well. The drop in temperature means the LHM becomes less runny which tends to show up partially blocked filters. Not really the weather for messing about with cars but cleaning the filters and putting in a dose of hydraflush would probably help.
Rory

tomsheppard · Unread post by **tomsheppard** » 08 Jan 2003, 20:18

In theory, the LHM is more viscous but with a pump running at the same rate, the temperature is not an issue. I think that the reverse applies, sinkage being faster during hot weather. Lightly blocked filters sound likely to me but I don't know if the LHM is at all hygroscopic or if there is any chance of condensation in the reservoir with Ice crystals forming in the system?

madman · Unread post by **madman** » 11 Jan 2003, 14:07

LHM does not retain the same viscosity at lower temperatures. If the LHM is old it also thickens. If anyone has access to aircraft mineral hydraulic fluid with an OM15 or H515 designation then use that instead.
The aircraft stuff is red in colour but has a far wider viscosity range, down to minus 40 at 35,000 feet! I have used this fluid in both CXs and BXs with great success.

John F · Unread post by **John F** » 08 Mar 2004, 02:43

Hi Tom, LHM is not hygroscopic and cold weather should not adversely affect it. I ran a BX in Austria one winter when we had -30C for a couple of weeks and it stood over night in an open car park at the side of a lake. Only two things I did was to put Citroen additive in the fuel and turned the ignition key to heat the glow plugs once before I went thro' the full start cycle.

AndersDK · Unread post by **AndersDK** » 08 Mar 2004, 03:05

The pour point for LHM is -62 (celcius !)
Boiling point is +255'C (at open air pressure)
The LHM fluid - despite it's mineral oil base - has oustanding viscosity temp range.
Any use of other hydraulic fluids would be useless - unless LHM is not available.
LHM is NOT hygroscopic - but water condensation inside the reservoir tank is definately a possible problem.
Any water inside reservoir tank will more or less block the filters - as it freezes on to the filter meshes.
Exactly the same can happen to the filter meshes in the fuel tank suction pipe - but here it's a bit simpler to solve the problem adding methylated.