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This is why u should do ur home work this will work but unnecessary as the powersteering unit in the vl self air rates the bubbles of air raise to reservoir and pop when it stays at same level no air is in reservoir and you should jack car up so both front wheels off turn fully both ways 2 3 times and that ways in gregory handbook also states 0.9 litres capacity not 700 mlsFluid capacity is about 700ml.
I would not try and drain the system and then refill as this will cause a lot of trouble with air in the system. Rather just flush clean fluid through the system by
1. Draining the reservoir, then remove the return line and stick it into an old plastic 1.5 litre coke bottle (or something similar) and block the return port on the reservoir.
2. Fill the reservoir to the top with clean fluid, then start the engine and run it till the reservoir is almost empty (will only take a couple of seconds).
3. Repeat number 2 above a number of times whilst turning the steering wheel left and right (easier done with the front of the car jacked up off the ground) to cycle clean fluid through the steering rack.
4. When complete, re-attach the return line to the reservoir and top up.
I would suggest only flushing through about a litre of new fluid. Then top up and drive it around for a week or 2 and then repeat the process.
When turning the steering in step 3 above do not go all the way to steering lock as this creates excess pressure in the steering system which might create a mess.
If you do get air in the system then flushing it out will is a PITA, basically you need to keep the fluid topped up and cycle the steering left to right. Air/fluid returning to the reservoir will tend to come out of the top of the reservoir. If it is really bad and the fluid becomes aerated then you will need to just stop and let it settle before continuing to bleed the system.
If crap in the fluid/system is the cause of your problem then also consider fitting a filter in the return line after flushing clean fluid through it. Something like the Magnefine filters work well.