power steering gets stiff now and then ?

My almost 1 -year old Hyundai I20 with electronic power steering is used as a driving school vehicle. It has no problem with normal driving, but when we are practising parking and reversing over and over again for two hours, it gradually gets stiffer and stiffer until we have to stop the lesson. I am going crazy with it because I can't give good service to clients like this! Hyundai have replaced the steering rack, and checked it over and over again, but nothing solves the problem. It improves for a short while, then starts again. Now someone suggested I rather go for a hydraulic power assisted system, which will be less economical, but apparently is not going to ruin my business.

So fed-up!
June 2012

Does the car have electric or belt-driven power steering? Could be a slipping belt or the alternator over or under charging.

hhh
March 2012

not sure on your model but would check fluid reservoir first for oil

cdc
March 2012