For the TS Astra with hydraulic-electric power steering, it takes a Pentosin CHF fluid. A couple of equivalents I have come across include Castrol Hydraulic System Mineral Oil Plus, and Penrite LDAS fluid.
I would be surprised if the noise was actually coming from the power steering as the engine rotation which drives the steering pump is always the same, sounds like its more likely to be a gearbox issue
If it was ordered with power steering it would have it.
Bad power steering pump
* No power steering fluid in reservoir * The power steering pump is not operating
to my knowledge there is no power steering filter i would check my power steering fluid level
From what I understand, power steering in cars (vehicles) is simply to make steering the car easier. If it were not for power steering, you would have to use a lot more muscle to turn the steering wheel than you use when you have that power steering in place!
wheels at angle put most stress on power steering pump, or rack and pinion. low fluid or bad pump, rack and pinion would be your problem.
If you have an electric power steering system, that means you HAVE NO FLUID. Therefore no fluid to change in the 1st place.
could be several places, power steering hose, rack and pinion (or steering gear box) or power steering pump.
the most likely cause of that would be the power steering pump failing.
After bleeding the power steering the pump may make a noise because there isn't enough power steering fluid in it.
You'd have some steering issues, and your power steering pump would eventually burn out.
No power steering fluid, broken pump, or broken lines.
check the power steering fluid level. I would have to say your low on fluid.
Power Steering Fluid Or Power Steering Pump
on the steering column beneath steering wheel
My 2010 Ford Escape's manual says it has electric assist steering.......would it even have power steering fluid?
Check for a loose power steering belt.
reroute the line around the power steering cooler
Your power steering will fail because brake fluid is poor lubricant.
Power steering belt slipping?
You might want to check your power steering fluid
your power steering fluid return line, also known as your power steering low pressure line, may have a hair line crack in it and need to be replaced.
This is your power steering pump failing, I would suggest replacing it sooner rather than later.