I always search for answers first, lots of knowledge on this and other websites. But I always like to post, to see if the more mechanically inclined members here concur, or if any aspects of the issue 'click' and lead to a consensus solution.
The plan is to inspect the trunk and the area around the tank and under the carpet tomorrow. Then I'm going to replace the cap and top off with distilled water and drive it, to see if it is still heating up as much, hissing, condensing, etc. Assuming the cap solves the issue, I will do a pressure test and have the coolant flushed just to be on the safe side, since the 50/50 mix will be off after I add that much distilled water.
Hopefully, it's just the cap. But if not, then I will be checking the water pump, and looking for leaks.
Thanks again for the input everyone!
