The beef should be with Suzuki because they have fail Sam Ham too by saying that they forgot to log his complaint or some jazz like that.  That's not right and everyone knows great service goes a long way.

Does your state have a "Lemon Law"?

Would the dealership or at least the company have to recognize a problem with the vehicle in order for the "lemon law" to be in effect?  I believe you said the dealership could never find anything wrong.

Hampster, I know it was an "out there" idea, but did you ever see my post/email about a possible "hot spot" on the head (maybe from a clogged water passage or something)?  I thought that might have made a cylinder hot enough to knock, but still have acceptable overall water temp.  Just a thought.

BTW, I had a 1990 Dodge Caravan that would occassionally stall when the A/C was on.  I never got an error code.  I changed sensors, ignition components, etc., and could never solve it.  I had it at several car shops and dealerships and no one could find anything wrong.  It even stalled while one Dodge dealership had it on their computer... no error code!  The wife got tired of stalling, so I finally sold it.  The guy who bought it was never able to figure it out either.  I feel your pain.

That's on my "to do" list.  I thought about it too.  Might be some crud up there just enough to make part of the head go hot but not enought to spike the tgauge.  BTW, the scan tool showed 191-194 temp (measuring the ECT sensor) at idle after a 10  minute test drive.  Still there could be some hot spots up there like you said.  

WOrth a try anyway, got nothing to lose and its time to dump the old coolant anyway.

The problems with new Suzuki dealers isn't isolated. My grand father had bought a new 2002 XL-7, only 12K on it when the AC unit blew. Suzuki told him that was to just to bad.
 Grandfather got mad and traded it on a dodge caravan.  Happy now.