09-29-11, 01:33 PM
Maybe this is normal, but this seems like its the first year for this happening. My 02 deville that I've had for quite a while now, will jump to one notch above the midway mark on the temperature guage. It only happens once, and for maybe 30 seconds before going back to normal. Its still 90ish here in South Florida, and my commute to work is about 30 miles one way. It usually only happens once during the drive to or from work, but usually just on the way home. The other cadillacs i've had would do this is I were stopped in traffic, but not at 60-70 mph like now. Coolant level normal, doesn't go down because i check it regularly.
09-29-11, 01:52 PM
I would start off by checking the purge line to make sure it's not blocked. Disconnect the line that connects to the top of the overflow bottle. Remove the radiator cap and stick this line in the neck of the bottle. Start the car and make sure you have a steady flow of coolant coming from the line. The purge line is the line that bleeds any air bubbles out of the cooling system.
Have you done any cooling system maintenance lately?
09-29-11, 04:10 PM
Base Deville models have even more highly-damped dash indicators, that means the "center" of your temp gauge means anywhere between 187-235F.
Follow above advice about purge line; also check if your condenser/radiator area is clean, free of dirt/dust buildup. If you haven't done it, using an air compressor, blow out all the dirt and dust accumulated between the radiator/condenser fins.