Power steering rack leak...

[tam_bui]

Hello,

I brought my car to BMW dealership for dealer's inspection 2 weeks ago as part of my contract to buy a car and the BMW dealer said that my car has power steering rack leak and it needs to replace the whole assembly.

The dealer where I buy the car from agrees to fix with their own contracted mechanic shop and subject to BMW dealer's inspection against the fixes.
2 weeks later, when they bring the car back to BMW dealership to reinspect the power steering leak, BMW dealership cannot see the leak and the seller said that their contracted mechanic shop could not find any leaks claimed by BMW dealership.

So, I am not sure who is right? How can I check for power steering leak? Is it a serious issue?

Thanks
Henry