1989 318 coolant issue

It sounds to me like you're simply filling the cooling system too full. What you have is not a coolant recovery tank, but simply an overflow jug. There's a difference. A recovery tank is a part of the pressurized system. An overflow jug simply does what its name implies. You need to fill the radiator so that it is about 1" from the top. This will give it the proper room for coolant expansion. If the overflow jug has coolant in it and the radiator is slap full, discard the coolant in the jug and drain some coolant out of the radiator until it's 1"-1.5" below the top, then it will be filled correctly. Try it then and see how it does.