Q. I plan on trying the Blue Devil in a '92 Acura Vigor 5cyl engine with leaking head gasket or cracked head or freeze plug. Leak occurs after full operating temperature reached but not every time! Any hints/helpful comments or history of it working in that particular car???

A.   As temperatures rise most materials expand- leaving room for a leak.  Factors such as age, miles (highway or home base) and environment temperatures can contribute to the inconsistency especially if it is a small leak that you've just noticed. 

Tips:

1.  On top of the normal directions. Flush.  Remove Thermostat.

2.  Pour Blue Devil SLOW.  Count out loud- up to 1 minute.

3.  Drive after 50 minute install.  The longer the better.  Get on a highway. 2 hours +/-.

4.  Leave Blue Devil in system overnight.  Drive in morning.

History?  Fixed over a million cars in a decade. Check out the testimonial videos.  

 I do not have stats on that car specifically. 

One of the biggest differences between “old” cars (those built before the widespread adoption of electronic fuel injection and computer controls in the mid-late 1980s) and “modern” cars is the warm-up.  If your car was a few years older I would suggest 3 minutes or so warm up time prior to the installation.  During this time the choke would turn itself off and engine will settle into a stall-free idle.   With your car- 30 seconds is fine after initial start up.