[Excaliber]

One of the things Evan's coolant recommends, for max cooling affect, is to block off the by-pass hose. Based on that I would have to guess a by-pass is a non-critical component when it comes to cooling. It may even prevent max cooling because of it's recirculation flow.

I think it's primary function is to supply hot water quicker to the heater/defroster (on normal cars)?