Thank you ,LRScott, for the detailed instruction.We will try this method. I will let you know what happens. Do you think I can rule out wacky BECM or any electrical for overheat?

 

If the becm is malfunctioning, you would know it. There would be a lot of other weird things occurring.

The only way to rule out an electrical problem causing the gauge to read in accurately is to check the temperature using an OBD II scanner capable of reading the vehicles real time data or an infrared temp gun. Using an infrared temp gun is going to be the most accurate and probably the cheapest way, unless autozone or the like has an obd scanner you can borrow that reads engine temps. I would try not to drive it until this is resolved. If it really is the HGs, then the problem will only get worse and will eventually lead to block failure.

Start with checking the spark plugs first, its the cheapest/free first step in diagnosing the issue. If they look fine, move on to the next possibility, if one is steam cleaned or you see coolant on one, then it definitely is the head gaskets and you can decide what you want to do with the rig from there.

This is a spark plug from a cylinder that had a blown head gasket. Notice the build up on it

http://ww2.justanswer.com/uploads/AU...spark_plug.jpg

 

I havent driven it at all only to and from mechanics in last year in and half. I stop if I see gauge going up. Weird things have happened. The weird starts,bulb failure, radio and HVAC display dim, heating and cooling intermittently working, air supension sometimes works and sometimes doesnt. Its pretty crazy...I know these RR have a mind of their own. I just washed her...maybe she will be happy and function today.....