Do not quite understand Leathermang's comment. I have always heard that bubbles in the sight glass mean you are low on freon, therefore you need to add freon. (I also seem to remember reading something in the forum lately, probably within the last 2-3 weeks, that said you add freon by weight and not by pressure but that might not be correct.) You might want to do a forum search to clear this up.

I do not know how much a 300D holds but I just had freon added to my 81 300SD. It was cooling but not quite enough. The indy added two pounds and said that the 300SD actually holds a total of 3.1 pounds which is quite large.

So maybe 8 ounces is not nearly enough. But then again I do not know about the 300D.