Recently replaced vented mandrel and new blades, everything is fine until yesterday, before putting the blades in engaged position the blades are already running, and the belt is making a noise. I checked the bolts on the mandrel to make sure they are tight and the belt is tight, what am I missing, that is causing the blades to engage when in the disengage position? The mower is 2 yrs old the reason the mandrel was replaced is because my son hit something and broke the vented part which holds the mandrel in. The deck was taken off and cleaned and inspected before all of the new parts were put on. :confused:
Thank you,

Two things to check. Verify that you used the correct OEM belts and also check the blade brakes to insure they are properly installed and making contact with the assembly.