If I crank up a cold car, the icon for overheating starts flashing, as soon as the engine got a little bit warmer, the light just goes off. I just changed the old black temp. sen. for the green one. What can be wrong??

 

Is it the overheating sensor or the low coolant sensor? If it is the latter, the reason is the problems in the coolant reservoir (translucent tank on the pass side of the engine compartment) corrode. You can try cleaning them with a piece of emory cloth attach to the end of a dowel, that should take care of it.

 

could he just be low on fluid? low enough to cause the light but once it warms/expands its showing the right level?

 

the icon blinking after cranking the cold engine on is the same like I have on the water temperature gauge.
the part I changed is water temperature sender(green one) and it didnot help

 

Like on this list? Its either low level in the coolant reservoir, or a dirty sensor. NOT the one you replaced, its in the reservoir.

 

yes, it is the 6th icon from top( coolant temp. warning light) Thank you guys for some ideas, Ill check out the sensor in reservoir.