ab_mach1· Premium Member
The 99's had a cooling issue, I believe. There was something with the coolant circulation on the driver's side head. Your Pop may have already fixed the problem they had. I found this...
The 4.6 two-valve engine coolant fill problem was "fixed" by moving the pressurized reservoir to the fan shroud, where it's at the high point of the system. The 4.6 four-valve engine still has a coolant crossover pipe at the top front of the engine, and you have to remove the plug in that pipe and fill the engine through the opening. If you simply pour coolant into the reservoir, it won't fill the engine. And despite the fact that the reservoir is pressurized, it may take forever to burp. The engine will overheat (and the heater won't work well in winter).