Or you can just take it out and tie the two ends of the hoses together. I had one start leaking on a fairly new MB while skiing in Utah in the dead of winter. I put piece of fiberglass tube in until I got home and it could be fixed under warranty. I know it is supposed to help provide the heater with hot water at idle but to tell the truth, I could never tell the difference even at the below zero temperatures I experienced at the ski areas.