Mine does that when it is overfilled. It will not tolerate even being a little too full when driving in a spirited manner. Sometimes it is hard to read the full mark on the side of the resivoir.
Also, if you think it is overheating (not likely), it may help to switch to synthetic power steering fluid. In the past I used Mobil 1 ATF but receintly I have been switching over to Valvoline synthetic.
