LHM change completed, but only after a brain wave

[adamskibx]

I had to improvise with oil a few weeks back, so decided to flush the system and refill with new LHM, only, I had used all the bottles up and had not filled the pipe. I managed to salvage some and top up the pipe. I have never done an LHM change and not needed to fill the pipe, but I have always done it with the engine running; as you fill the pipe you start to hear the pipe gurgle and the pump clacker, only it takes this LHM in and it seems to go into the abys, not raising the car. It was a good 30 minutes into the operation that I decided to fill the pipe with the engine off. Some movement of the bleed valve and playing with the height corrector lever later, it was raising and lowering as fast as I have seen a BX rise. It is amazing what a filter clean and LHM change can do. I won't be using oil again, unless there is an emergency, but it seems better now than when it was on it's old LHM. I guess the only concern with engine oil is what it can do to the low pressure return pipes. So, when you do an LHM change I think the strategy should be:

1) Lower car and release PR bleed screw
2) Remove filter pickup/return assembly, clean filters
3) Remove and empty LHM tank, cleaning everything inside so all you can see is clean aluminium
4) Refill LHM tank with two litres of LHM, return tank to bracket, use funnel to fill pipe and quickly replace pipe with filter union.
5) Put half a litre more in the tank and start engine
6) Put drive height on maximum, and gently screw in bleed screw (taking care not to burn your hands on a 14 exhaust! Ouch does that hurt!)
7) Wait, it should rise.
8 ) If not, re prime pipe with engine running and then stop engine, refill pipe and top up tank.
9) Bleed brake nipples if realistically possible in terms of nipple condition - I am yet to do this


That's it, it's just I have never understood what happens when you can't get the car to rise and you fill the pipe and the fluid taken in has no effect. Essentially, I think the trick is to fill tank and pipe with engine off, then hope and have a cup of tea.

[MULLEY]

The pump shouldn't make any clattering noise, that sounds like you haven't got enough lhm in the tank. I personally also prime the pump but with the engine on & only re-fit the pipe back onto the tank once the bubbling stops inside the funnel connected to the pipe. I also purge the air out the system by applying the pressure regulator on & off frequently as per the DIY section guide. Seems to work for me I would deffo bleed the brakes. I would clean up the nipples around the thread area, apply plenty of plus gas & let it soak in. I then use a hammer to bang the caliper nr to the nipple & give the top of the nipple a whack on the top of it. I then use a socket to gently start moving the nipple, make sure you work it backwards & forwards using more plus gas if it feels stiff to turn & gently try turning it out a little bit more than before, eventually it should come out. Heat is also another way to get a stick bleed nipple to move. If you round off the edge of the bleed nipple, just attach mole grips & follow the above proceedure, i would then replace the knackered bleed nipple with a shiny new one (i'd smear some grease on the threads before re-fitting as well to hopefully stop it from welding in tight again.

[citronut]

citroen used to state after working on the hydrauluic system,
run engine at idle with the bleed valve open for around 2 minutes, then hold the rev's at about 2.5k whilst shutting the bleed valve,

never used to have to prime the system, unless you were fitting a dry pump

regards malcolm

[adamskibx]

Thinking about it, the brainwave was only useful in so far as I made a mistake and used up all my fluid filling the tank. I guess your method would be better Mulley; fill the pipe (I didn't have a thin enough funnel so obviously could not get the volume required down the pipe without getting LHM everywhere), and in theory the system should take in what it needs to get all the way to maximum height, and then you could mostly fill the tank by dropping the height, I would guess.

My pump does make a clattering sound Malcolm. It can be heard as an addition to the sound of the engine as long as it's working and not on PR cut out. I don't know if this is normal but then it has done 111000 miles or so.

[citronut]

the pump usually clatters if it is sucking air,

if you mean a ticking this is more likely the accumulator sphere low or completely flat

regards malcolm

[MULLEY]

adamskibx - i don't think there is anything unnecesserily wrong with your method, if it works it works I literally follow the DIY guide method & its worked ok for me most of the time. Sometimes its a real barsteward to rise, other times its been quite straightforward, no idea why?

The pump deffo shouldn't be clattering, may very well be what Malcolm has suggested, the noise means the pump is working very hard to maintain pressure, so it will wear out quickly if not remedied & pumps are expensive 2nd hand if you want a re-con one. If only we'd known a few years ago, many pumps for all the models could have been saved for just a few quid each & everyone would have a stash for future use, but alas no

[citronut]

if it is becaue of air being drawn up by the pump, this mean the clattering is the internals of the pump are running virtually dry ( not being lubricated ) ,

unless of course the pump is titaly shot already

regards malcolm

[adamskibx]

I will have to have another listen. It was definately clattering but then this was at the point where there could have been air in there. I know the pressure regulator is good because with the engine off you can get maybe 3cm of rear end lift by moving the height lever up, so if it can do that I think it's got a good amount of nitrogen in it. I must look into the correct bleed procedure. In honesty I have never understood where the air is coming from when you release the bleed nut, as it seems to squeal an infinate number of times and yet the system is fluid, not air.

[RxBX]

...........................

That's it, it's just I have never understood what happens when you can't get the car to rise and you fill the pipe and the fluid taken in has no effect. Essentially, I think the trick is to fill tank and pipe with engine off, then hope and have a cup of tea.

Hi Adam.
If you've not seen/read the thread 'HP PUMP PRIMING' it's worth a look

Hopefully it maybe of help !



.

[adamskibx]

Thanks RXBX.... This blowing technique was something I tried actually in desperation, but the combination of grubby, possibly blocked pipe and my aversion to blowing anything up conspired to make me give it up as a rather mad idea that wouldn't work. Little did I know I was on to something ! I looked at the mechanics of it and thought; "yeah, that's a good idea", but it didn't work for me at the time. If the breather pipe was wider and clear of muck it definitely would have worked.