I haven't used any method other the taking the cap off of the tank 2 hours after driving the car on a very hot day. I heard a little pressure release.

I may be misinformed but I thought that I read something on the forum several years ago that indicated that this is a symptom of impending head gasket failure.

Admittedly I know less than nothing.

Thanks for the reply.

I have had the car about 12 years.