ok guys have a 2000 SLS with 143k on it.... runs and drives great, coolant service was done at the caddy dealer 30k ago, coolant is full. the issue I am having is that the temp guage stays at center unless I idle for more than 5 minutes then it goes up about the width of the needle. it will go back down (keep in mind I am still idling) after about 20 seconds to normally where it should be. what could this be? I am kinda stumpped. maybe a bad temp sensor or water pump or ????
I checked the coolant, no oil in there... checked the oil and no coolant in there. no smoke out the exhaust and no leaks at all. have not had to add any coolant it has stayed full.
any help is appreciated!!!

 

normal operation

as coolant heats up, the sensors turn on the radiator fans, coolant heat is removed, gauge temp drops.

 

ok just wanted to make sure...as I am not going to be doing a headgasket job what a nightmare! so the consensus is to keep it ?????? sounds like normal operation to you guys? ( not doubting you stomper) just dont want to have to do that major nightmare repair.