Originally Posted by PratoN
I assume that's referring to me - in which case, my clunk is pretty much non-existent... maybe I should have said "No".
I think you're on to something! It's probably that plate (or lack thereof) causing this issue.
You've checked your coolant overflow bottle to make sure that isn't the clunk, right? An ST owner (with the reinforcement plates) just eliminated a clunk he was dealing with by putting a wad of foam under the coolant overflow tank as a test.
Let me know what you find out, I could go back and change your response to reflect your findings.