JLK380 & JCD, I went home over the week end and looked at the by pass I did on my 300TD, and I noticed that I was mistaken about something. In the second para where I say, "coming from the water pump is a third line, cut this and insert valve."
Thats wrong, I apologize. Leave that line as is, insert the valve into one of the lines you just by passed, the one closest to the engine. If you already cut the other line, remove the valve and splice it back togeather with a short length of tubing and two hose clamps.
As I stated, I was going from memory, which for me ain't real good. I hope this has not inconvenienced anyone.