What would happen if there was no place on the cooling system for the hose on the overflow tank? The filler neck and radiator doesn't have anything to put an overflow tank on.

 

Coolant on the ground...

 

Let me get this straight... you have no provision for hooking up a coolant overflow bottle? What will happen is coolant system pressure will go through the roof, something somewhere will fail, and at worst you will blow your motor. You can get a header tank with a provision for attaching an overflow bottle at AWR.

http://www.awrracing.com/awr.html

 

you probably have a neck piece theat is the wrong one or plugged with a bolt or somnething.

When I got my 86GX first thing I did was go to change fluids etc. when doing the coolant I noticed the same thing...the overflow hose was not connected. I sat there staring at it for a few minutes trying to figure where/why it was not connected. Turned out at some point they had snapped the nipple off the filler neck and had screwed a bolt into the hole. Looked almost stock hehehe.

Went down to local MAzda parts store and picked up a replacement filler top with nipplle for a few bucks swapped her in and hooled up the overflow

Anyhow whatever the reason in your case fix her up now as wothout it the pressure and overheat flow has nowhere to go and you will at worst blow a coolant seal