Ive read a few topics and i think our S3 needs a new one, even though the last one was replaced in 2006, 35k ago. A friend of ours doesnt think it is the water pump, so is there a definitive way to test/check to see if its failed/failing? Symptoms are:- Doesnt overheat on tickover no matter how long its left running. Doesnt overheat while driving below 2000rpm in any gear, so is happy to cruise along at 50mph in 6th. Only overheats at revs more than 2000rpm and then coasting in neutral will soon bring the temps back down again. Fans are working ok, so not a fuse. Water levels are good too. Some people have said look for a "jet of water" in the expansion bottle. Here's a video (we added an extension tube to make it clearer). Is the jet as strong as it should be? http://www.youtube.com/watch?v=fK2wR4FnDok Seems to have a steady flow on tickover, increases when the revs rise, then dies down again when revs rise further. Im not 100% sure this will help diagnose as i know it doesnt overheat on tickover even when revving constantly at 3000rpm. Any tests we can do? Any help appreciated.