My Galaxy has had this problem for 2 years and the correct diagnosis has been missed by 3 different highly recommended garages! Perhaps they all thought me a soft touch and made a bit out of me on each occasion. Hence I thought I would share my experience.

The symptoms start with engine noise when reaching full lock on the steering. The engine labours rather heavily and runs unevenly when reaching full lock. The symptoms are worse when the aircon is engaged. As time goes on this starts to get worse and then the noise develops from a judder to more of a squeal. The noise starts to appear at all sorts of times when the engine is under load but at low revs, such as steering locks, straight after starting, engaging aircon. The noise comes and goes intermittently. At one point the noise got really loud when the belt tensioner started to knock on the tensioner travel stops whenever the engine was ticking over.

The correct diagnosis is that this is all related to a faulty pulley on the alternator. The pulley has a free wheel mechanism which commonly fails. A new pulley costs about £60 in parts and 1 hours labour. I discovered this when eventually the pulley exploded off the engine while commuting to work, last seen bouncing into a gutter on a dual carriageway. On fitting a new pulley, all the symptoms dissappeared and the engine ran better than it had for years. The mobile mechanic that fitted the new pulley for me said it was common for this problem to be misdiagnosed and he described perfectly all the symptoms that had led to the final spectacular failure.

Misdiagnoses have included replacement of the belt tensioner (twice) which brings some temporary relief from the noise, allowing the garage to claim they have "fixed it", but only because the spring is nice and new, and it soon gets worn out by the bouncy cable running. Also numerous checks of the power steering pump and aircon system, with various flushing, topping up, cleaning etc. One garage even started to look at the wiring loom that runs the injectors, claiming that it was common for this to perish and then the engine will run badly at low revs. Waste of money that was.

Final note is that it is now almost 2 years since the pulley failed and now the alternator has failed. A recon alternator cost me £160 and comes with a new pulley already fitted. My advice is to replace the whole alternator if you have this problem and intend to keep the car. A pulley replacement is cheaper but will outlast the alternator.