When you make hard turns it makes a mooing sound?

The car seems fine whilst driving but when parking the car when you make hard turns it makes a mooing sound. It's electric steering according to the mechanic and the noise he says is the electric sound and compared it to a mini. He says there's nothing wrong with the car (he is part of the same company as the sales garage). However, it doesn't sound like the high electric whine of a mini and more like a groaning/mooing noise. It doesn't sound like the noise it should be making. We are worried that the steering will fail or be costly and we have just bought the car.