thermostat m44 engine removal / symptoms

[handsomejackuk]

Hi,

bmw z3 1.9 air condition electric fan 1998

recently noted that my temp guage is a bit erratic and goes from middle of guage when in traffic, to cold when moving along and going down hill , and back up to the middle when under heavy load i.e. going uphill...

I beginning to suspect thermostat... looks like mine is plastic housing. and theres no viscous fan so easy to change would the above symptoms suggest a dodgy thermostat... ?

thanks

[Del]

Yep - the moving into the cold zone when the engine is not under load and you are travelling at a reasonable speed - is typical. Several things can cause an engine to overheat but for it to overly cool is typically the thermostat.