1989 318 coolant issue

I;m not gettin into a pissin contest over technicalities. If it's not a part of the pressurized cooling system, it's not an integral part of the cooling system and has no bearing whatsoever on filling the radiator slam up. Call it a recovery tank, an overflow jug, a puke tank, whatever you want to call it. Unless it's pressurized with the cooling system, the radiator must have some space at the top of the coolant level for expansion. Period. If you're filling the radiator slam up, that could be what's wrong. Post #17 is a suggestion that has ZERO COST. THERE'S your clue. I always start with the free or low cost options, because 99 times outta 100 that's where you find the problem. But what the heck do I know? I swear, some of these guys have nothing better to do than come on here and make things so complex and convoluted, no one ever knows what the right answer is. The fact is this is the internet and nobody "knows" what your problem is, but the free/cheap stuff IS the place to START. Good luck. I hope you figure it out.