Ross, thanks for the suggestions. The leak is definitely coolant, and the floor gets flooded, lots of it, enough to spread out 3-4 feet and it keeps coming after the machine is shut off. I will re-level the machine high in the front and see if that helps. Right now the table is level within .001" side to side and front to back. I set it up that way because I am truing up rough castings using a 4" diameter face mill, and it helps to be able to use a level when shimming up the castings on the table for the first (reference surface) cut. The previous job was machining some discs (farming implement) which had a domed surface. So for both jobs the coolant was flowing towards the column a lot. However, I did not see much coolant in the trough around the base and I did not see a lot of drips onto the floor.
Thanks for the education on the drainage around the screw. I have never had that cover off, did not know it existed. Inside it was clean, but maybe that just means it has been seeing a lot of flow. It looks like the compartment drains to the rear catch basin, but it also has two overflow drains that appear to go out the bottom of the machine. It also looks like the high water mark is about the same height as the overflows. Here is a picture:
I suspect that coolant flows out through the gaps around the column, and from there it finds its way into the front compartment:
And I am also thinking that the rear catch basin would not overflow into the drain on the left before the fluid level in the front compartment overflows:
You can also see the high water line in the rear catch basin.
So what else should I look at, is there more to it, i.e. additional paths where coolant might flow?
I'm a bit suprised that this problem does not appear to be more common, judging by the lack of replies to the thread, which makes me think it is probably not as simple as re-leveling the machine and draining the rear catch basin more frequently.