Re: WATER in taillight and leaking through tailgate...
If you have the first generation Equinox, then I would say that you should check your spare tire well...do you have water in it? Is water leaking inside the vehicle?
If the above is all true, then search this form for "water spare tire"...you'll find a few threads. The one about a 2006 Equinox has a service bulletin posted in it with diagrams of where to check for leaks. There are 5 or 6 places to check, if I remember correctly. There is also another thread about a 2010 vehicle, but it didn't really end well for him.
2011 I4 Equinox LS bought 3/31/11 : after multiple failed repairs for stalling/start-up noise issues, pursued a GM-assisted replacement. GM agreed, and paid several thousand dollars to get me into my current vehicle...<br /><br />2012 I4 Equinox LS bought 02/28/12