Do you have have an IR temp gun to help get the temps of the various hoses and block?I'm having an intermittent overheating problem on my 05' T-reg. It's a 4.2l V8... But after I turn it off, then start it again, the temperature gauge shoots up and says it's overheating...The lower coolant hose never seems to get hot...I am at a loss as to what to do next to diagnose and fix this problem.
Do you think you have air in the system; have you run (not drive) the engine with the coolant ball cap off.
What level does the overflow ball show when cold?
Hoses can appear fine on the outside but could be collapsed on the inside.
How old is the coolant and is it the pink G12/G13+ and is it mixed at the right ratio?