I understand it's a well-beaten horse. And i have looked online before asking. I had a recent headgasket replacement done on my '02 Disco. I've tried everything I can think of to bleed the air and still have the "waterfall" noise in the dash. After the HG replacement drove it with no issues until the following day when the temp jumed quickly after about 15 minutes of driving. The oil is clean (no milky coloring), nothing from exhaust, and I did the block chemical test with nothing evident. Any tips or tricks on troublesome issues getting the air out would be helpful.