[1991 Corvette ZR-1]

If you are talking about the large bolt securing the rack, I did not bother that one until the cooler was out of the way. The wrench size appears to be 18mm for that fitting going to the rack from the cooler. There are four 10mm bolts holding the cooler on. It is pretty light once you undo the last bolt and I kept mine level taking it off to set aside. You may not have to remove the cooler, just the line from the rack. I removed my cooler because I wanted to also remove and clean the bar assembly the cooler bolts to. As long as you remove the fitting from the rack, you can let the cooler hose hang free.

With the cooler line off the rack along with the high pressure hose coming from the PS pump, the only things left are the main bolt and the smaller two bolts on the passenger side. I pulled the rack out through the driver side. The FSM does not state to remove the cooler but I had already introduced air into the system at that point anyway and with it off I had more free room.