Hi everyone, I was recently driving when engine started over heating, and coolant light came on. Immediately pulled over and checked the water, it was fine. I gave it half an hour and turned the key and all warnings had gone, considering I was quarter of a mile from home, I decided to risk it. Long story short, water pump had gone. Last night I did water pump and timing belt, and when I got to the TB/WP, the water pump sprocket just fell off in my hands, before giving me chance to mark crank/cam positions, so I had to do it the old way of finding TDC BDC with a screw driver hanging out the cylinder head. Anyway, timing was done and correct (it was way out when I took the thing apart). Next was WP. Undid the bolts and yanked at the pump and a flow of a 50/50 mix of G13 and plastic impellers hit me. I scooped out as much as I could see/feel and put in the new WP, everything back together, turned her over and she started no problem! Phew, timing is good. However, I get a funny kind of knocking/banging noise which sounds like its coming from around the serpentine belt area, but I can't get it out of my head that it's the new impeller eating bits of the old impeller. It's possibly important to note that I also replaced the serpentine belt at the same time. Also, after running the car for a minute or two, I noticed that no water was circulating. I have a blockage, or the pump is kaput already. Firstly , how do I flush the whole cooling system? Is there any way to get these damn impeller bits out for good? Secondly, Would you expect a constant knocking if something was hitting the impeller? Could it be bearings in something on the auxiliary since I've changed the belt and everything is tighter? Thirdly, why on earth did Audi design the water pump to run off the timing belt?!?!! It boggles the mind.