I just recently purchased a 1991 350 SDL and was anticipating overheating problems because of previously owning a 350 SD, I got the SD squared away with new everything. Because of the SDL approaching the 120 mark in town traffic I first addressed the AC aux fans now I have just replaced beginning with the heat sending unit first, thermostat second and finally, radiator, water pump, fan clutch, new G-05 coolant. Took it for a test run in 100 degree temp yesterday and she never got to 100 degrees. The problem I did have was the expansion tank light showing low, the coolant is actually fluctuating in the tank, it goes down with on road driving and comes up when driving slower speeds or when parked. I have researched the forum and read about this problem and are assuming that there must be a void in the system that hasn't gotten the air out. There were several methods discussed for dealing with this, I would appreciate anyones advice on how to stabalize my system so the expansion light won't keep coming on.
Thanks in advance,
Frank