Old thread, but Kaldek's videos have been very helpful for me. Kaldek, I owe you a beer or three. Here's a photo of the internals for reference...I took mine apart (sixth gen) last night to see if it needed servicing, but I honestly can't see how this unit would ever fail. It's just a spring and some metal bits. Mine looked brand new inside.
Now, that said, the coolant passage was almost completely plugged on mine and wasn't allowing the unit to heat up properly:
Before:
After:
Now to go buy some circlip pliers so I can get the bloody thing back together...
