In Reply to: Gunk in Radiator coolent posted by Mike on January 01, 2001 at 09:12:15:
I agree with Alex on the drain and refill; I'd also throw in 2c and say that all older vehicles I've had seem to get some "gunk" in the radiator overflow tank at least - looks like pond scum for lack of a better word - and these engines have all gone A-OK for 50000kms plus...
This is the case with the 87 735 as well - there are blotches on the level tank but the coolant is clear and looks good, so unless you have major scum on the actual liquid or definite slime and/or whitening (oil+water = white lathe lubricant, try it) don't get too worried is my approach. BTW, also in my experience expect changing brands of antifreeze to "loosen up" (read disturb sedimend, gunk, cause small weeps around hoses) the cooling system, so you might want to stick with either as close as you can get to the original antifreeze and/or as weak a mixture as you can get by with (at first - you'll want a reasonable strength for the long term to get the corrosion inhibitor coverage).
I hope this makes some sense. Do also check the archives for the coolant bleeding and heater damage/failure gotchas. Good luck.