hi guys
i have a 2004 with manual trans,i have about 160k km on it,recently the temp gauge has been doing weird things,i am running my smarty on tntr on setting 1 everything default,i also have a scanguauge that shows coolant temp,when its warming up it goes to about 170 then it will drop to maybe 140 then slowly go up to 160ish then drop again,it seems to drop about 20-30 degrees then go slowly up,on the dash gauge it almost goes to startup temp then close to operating temp then down,sometimes it will go to operating then stay like it should then next startup it will do the same bouncing temp,it never goes above operating temp always below,i think its affecting my mpg as it rarely gets to operating temp,i installed a new tstat and it does same thing,what else could cause this weird issue,?? thanx guys
dave

 

Maybe a loose or bad wire going to the temp sensor. Or maybe a bad temp sensor....

 

ok i will look into that for sure,hope it something simple like that,thanx