1. Clean the TWO filters in the LHM reservoir.
2. Check that the pipe from the LHM reservoir to the pump isn't leaking air in at the connection on top of the reservoir (the pump is sucking LHM through the inlet filter).
These two things are linked. When the LHM is col, the pump has to suck harder (greater negative pressure). If the filter is dirty, the pump has to suck harder. The harder the pump has to suck, the more likely it is that air will get sucked in at the connection on top of the reservoir.
The problem with the crankshaft pulley is that it is made of three parts: 1. the steel inner (bolted and keyed to the crank shaft); 2. the grooved steel outer ring that drives the belt; 3. a rubber damping ring that is bonded to 1 and 2 and thus transfers the drive from the crankshaft to the belt. With time, heat and miles, the bond eventually breaks so that under high load, the outer slips relative to the inner. Once this starts to happen, it's not long before the pulley fails completely!
I hope this helps
if theres any new I'll write it!!
. Then I checked the pulley again and the mark was straight. It seems the pulley is ok but I'll recheck it on a week. This time the stop and caution lights showed up again after 8 - 10 minutes of driving. When this happens I can't hear the pump but some (1-2) minutes later the lights go off. The steering progressively softens as it warms. 
