Well thanks to all for the input. You guys that understand the anatomy of the 606 head all nailed it. It is indeed coolant I drilled into. I feel like an idiot thinking it was fuel. But I guess the odor of fuel was already so strong (I had to remove a few fuel lines to gain better access when drilling) that I just convinced myself I was looking at diesel fuel.

I still like renaissanceman's suggestion of trying to plug the hole with a set screw. I think what I will try and do is list it for sale as a part's/project car. If someone comes along that wants to attempt this I will sell it and be done with it. In the meantime while waiting for a buyer I will tinker with it when I have spare time on weekends in the coming months, trying out his suggestion.

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Mike Mass
Freehold, NJ

1999 E300 TD 178,000 miles
2007 E320 Bluetec - Sold

1998 E300 TD - R.I.P.