On my 1994 mustang. The car all of a sudden would like to get hotter than is used to get. On the (NORMAL) temp the needle used to sit between the N and the O. So I changed the thermestate to a lower temp one. Changed the radiator fluid. And don't run a/c. So could it be that it is so hot outside that the car will ruyn hotter than normal? (I live in houston).

 

how was your coolant level before you changed it? if it was low....look for leaks...find a pressure tester if ya can...

 

Yea, the hotter it is outside, the harder it is for your cooling system to cool your mustang. Like said above, if your coolant was low look for leaks. Make sure your rad isn't clogged too.

 

The water level was fine, and no leaks I looked. Maybe it is the heat from the outside.