Uh oh... Coolant leak. Possibly headgasket

[uscharalph]

are the gaskets on the expansion tank repairable?

You can purchase just the expansion tank only, so you must be able to get gaskets

[Peter Mac]

How does one remove the clear plastic expansion tank from the radiator, and were are the seals, are they around the sensor.

[Dan in NZ]

Check carefully where your leak is coming from... I thought my expansion tank was leaking, but it was actually a crack near the bleeder screw, which is part of the black plastic bit. If it is just your seals, I have a pair of expansion tank seals that I didn't use (just got a whole new radiator, about NZD$300).

For a better look, there's a metal plate that surrounds the top of the expansion tank, it comes off easily with an allen key.