Here is a DIY Specifally for Replacing the 2003-2007 Honda Accord V6 Drive Belt
Use this DIY to Replace the Drive Belt and the Drive Belt Tensioner on a 7th Generation (2003-2007) Honda Accord
2003, 2004, 2005, 2006, 2007 Honda Accord Models
larger wrench for double wrench maneuver
new tensioner pulley
Move Power Steering reservoir by lifting it and pressing tab with flathead to remove.
If you have proper tensioner tool, use that, if not use the double wrench method. Take 14mm wrench and larger wrench to rotate tensioner clockwise.
Remove belt from over power steering pump. Once off that pulley slowly release pressure on tensioner. Now remove belt from other pulleys.
Step 4 – If not also replacing tensioner pulley please skip to step 6.
Remove tensioner pulley by using the above double wrench maneuver. It is a single bolt. Turn counterclockwise and once broke loose slowly remove being careful not to lose inside nut.
Place new pulley in place and before inserting bolt reach around behind it and hold nut in place so to not lose it. Once pressure is applied to nut insert bolt and get it started by hand. Now remove hands and once again use the double wrench maneuver to tighten. I do not know the exact torque specs but I figure whatever torque it gets while replacing belt is enough.
Start rerouting the belt at the bottom on the crank pulley first and across the bottom on to the ac and work your way up. Place the belt on all pulleys except the power steering pump pulley.
Once the belt is on all the pulleys except the power steering pulley reposition your 2 wrenches again and rotate them clockwise to give you some slack on the belt. Once you get enough slack carefully place belt over power steering pulley. And remove wrenches.
Replace fluid reservoir.