I replaced the expansion tank as per the instructions on this board.
Got a new Meyle tank for $57 on eBay. Seems well made, comes with a level sensor. The sensor has a protective sleeve. At first I was going to remove it but it seems to be part of the sensor. There is a hole top and bottom so it should work. Did have to pick out some black plastic swarf out of the tank after I had installed it.

When I refilled the cooling system and fired up the engine everything looked fine (the new sensor did not give a false signal) until I touched the upper radiator hose were it connects with the radiator. It hissed and leaked. I let the engine cool down. I did not find any cracks in the radiator inlet fitting. I repositioned the hose and made sure the clip was on parallel to the radiator. Now it is leak and hiss free when I press it. The hose is 13 years old and pretty soft but otherwise OK.
What was that hissing/leaking all about? I am thinking of putting a worm drive clip on as extra to the metal clip.

 

Two thoughts. One, stay away from worm clamps, especially on upper and lower radiator hoses. Go with tension clamps.

Second, might be time to consider changing that hose, especially if you can easily slip the hose onto the radiator hose fitting.