Simply remove the bolt from the top of the t-stat housing as you add the coolant. When the coolant flows out of the hole with no air, replace the bolt and you are done.

BTW, I suppose you noticed that popular opinion says NOT to use green coolant.

And when you replace the fan shroud, be sure all the little pins are seated in the holes after you turn it to lock it in place.

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2012 E350
2006 Callaway SC560