I bring it in to my mechanics about every 3 months for a complete digital exam. I just had it in on August 14. The only thing that cropped up was that the coolant wasn't charging as cool enough as it should so they took care of that. It's possible that whoever worked on it screwed something up as it was fine before that. Beyond that, it could be 3 or 4 other causes, like a vacuum hose to a compressor bearing.

I've been monitoring it and plan to bring it in.

Cathy