Thermostat bad or not? Goes to red when warming up in driveway??

[02BMWX5]

OK so I have a X5 with 143,000 miles on it

It has recently went to red while I am warming it up in driveway

I turn it off and it goes back to normal

It has done it while driving as well but is not overheating?

I just turn it off and re start it

It takes forever when warming it up or driving it for it to get to the 12:00 normal temp.

I can leave it sit in the driveway for 30 min and it will still be in blue

Is that normal? How long should it take for it to go to normal 12:00 on the guage?


Thanks

[jst2878]

takes my 2001 4.4 at least ten minutes to get to 12:00 point on the temp gauge.

[02BMWX5]

OK cool just checking I think the thermo may just be sticking causing it to peg to red sometimes or maybe a sending unit

It does better when I start driving it verses sitting in the driveway

I cannot figure out why it wants to stall when cold while backing out

The rpms just drop but when its warmed up its fine

[Isambard]

Sounds like a sticking/faulty thermostat, though its possibly an air lock. Can you get warm air through your vents?