You'll have to take the expansion tank out and I'd say that groton's kit will fix your issue, or after the tank comes out and you dry things out in it you'll see where the dislodged part goes back in and you can avoid buying their kit. If one of the sensors is floating in the tank you're going to register a low level on your dash. It can be a messy coolant spill, so I would recomment syphoning out of the tank and expect to loose some fluid when you disconnect it, but it won't hurt anything and will only smell a bit until it's all burned off after you drive it a few miles. Good luck.
--
1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.