Harbor Freight Tools - Quality Tools at the Lowest Prices
pick up the 94169 obd2 code scanner for 39 bucks,they will match the internet price if you ask.Read the codes and post them.Do it before you tear into the pump or filter so you find out clues as to what is wrong one item at a time.
Let's see what codes read and take it from there.

ohlord
water pump diy when he is ready
mybenz - Tips and Howtos - Benz Repair and Maintenance Tips - W210 - Replacing Water Pump - by Faizalza