Changing LHM filter without changing LHM

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Thunderbird

Changing LHM filter without changing LHM

Post by Thunderbird »

What's the simpliest and easier procedure to do this on a Xantia with anti-sink sphere?
Rgrds!
alan s
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Post by alan s »

Are you talking about the filter in the tank?
If you are, it's no big deal; just pull it off and change it end of story. If it is that one, why does it need changing though?
Alan S
Thunderbird

Post by Thunderbird »

Cheers Alan,
I believe that if the filter(s) is dirty the high pressure pump will be in overwork, and won't be able to remove the dirt from the lhm making the all hydraulic system work bad.
My idea was that if it was much easier (and cheaper) to just clean the filter(s) than doing the all operation of replacing the lhm, I could do it more often.
Any way, since I never have done the operation before, I'm not sure if there is only one filter or there are two.

Isn't it necessary to depressurise the system by unscrewing the 12. pressure screw, put the car in low position, and turn off the engine...?
Thanks!
alan s
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Post by alan s »

No, that only applies to changing spheres, but I usually do it anyway to get as much of the LHM back to the tank as I can.
The tank is exactly that, just a drum with a liquid in and the filter block fits into the centre of it.
I don't think it's all that wise a move to clean just filters and not change the LHM if the LHM has a bit of age on it and if it was dirty enough to be affecting the pump, it would definitely need a fluid change.
When the fluid is changed and even possibly just removing the two filters, it would be a good idea to also prime the pump before you restart and replace the jubilee clip on the feed line to the pump if it still has the non re-useable factory clip on it.
There are two filters in there; one that fits on the outside of some of the fittings and a cone shaped one that goes up the inside. An added hazard of just cleaning the filters also is the fact that particularly with the Xantia, there's a chance to get external muck falling into the tank and most of that would do more damage than internal contamination.
If the fluid has been changed recently, I'd look at doing filter cleans say every 12 months with a fluid change every 3 years, but be sure to thoroughly clean the outside of the LHM tank before you start to lessen the risk of getting external contamination in the tank.
Alan S
Thunderbird

Post by Thunderbird »

Alan, thanks for the excellent tips!
I will follow your recommendation of cleaning the filters once a year and changing the lhm fluid every 3 years.
The contamination of the tank also seems to be an extremely important issue - I'll be careful.
What surprises me more is how most Citroen garages just don't handle properly these important details, leading to the progressive destruction of the hydropneumatic system of most cars, and the degradation of the brand's image...
Even Citroen's official recommendation of changing the lhm and cleaning the filters every 5 year seems absurd!
Take care,
Michael
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Post by 406 V6 »

If you need any help...
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Post by spanners2005. »

YOU WOULD BE SUPRISED HOW ROBUST THIS LHM IS THE EARLY XANTIA,S WERE 5 YEARS OR 36000 MILES IT WAS ABOUT RIGHT ANY WAY MOST XANTIA WOULD OF HAD SPHERES REPLACED BY THEN OR LEAKS OF SOME TYPE OR ANOTHER (O/S FRONT SPHERE PIPE SPRINGS TO MIND) BE CAREFUL WHEN REMOVING FILTERS NOT TO KNOCK THE BAFFLE DISC OF BOTTOM OF PICKUPS OR IT WILL GIVE FALSE READING ON FLOAT. ALSO OPEN 12MM BLEED NUT ON REGULATOR WHEN FIRST START UP HELPS BLEED PUMP. ALSO USE GOOD QUALITY LHM (TOTAL OR BENDIX)
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Post by crapday »

cleaning the LHM tank and replacing the fluid was the easiest think I have done on my Xantia.
Thunderbird

Post by Thunderbird »

Is it necessary to bleed the brakes after the LHM change?
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Post by Kowalski »

Yes and no.
If you want to get more of the old LHM out of the system, bleed the brakes. The brakes are dead ends and the LHM in there doesn't come out when you do an LHM change, bleeding the brakes guarantees that these dead ends get their LHM replaced.
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Post by jeremy »

Another reason for bleeding the LHM through the brakes is to ensure it is up to specification so far as coping with heat from the brakes is concerned. Some water will eventuall get through the flexy's by osmosis and will contaminate the LHM. I accept it isn't as hygroscopic as ordinary brake fluid but I don't think this will affect the osmosis process.
If it comes out looking like new and better than the rest - then let me know but I'd be surprised if it did!.
jeremy
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