CEL will not stay off

i have an 02 gti 1.8t which recently has started throwing a p2181 code which has something to do with a coolant performance i tried replacing the sensor but yet the code still comes back even after i have cleared it several times

either the coolant resivour is faulty (for some reason 02 1.8t is a bad jeat for manufacturing the coolant resivour)

or the water pump is faulty ( rev it in nutral when warmed up to 5-6k fast and if there is a metal clink sound when you let off the gas the w-pump is bad) sometimes the impellar is not broke but when its gets really hot from highway driving or stop/go the impellar actually loosens itsself from the shaft and then cools down and re-attaches isself (its actually how they assemble them at the factory... pretty cheap)

is there anyway for me to check the coolant resevoir to see if it is faulty...i have not noticed that the car is running any different i have had no problems with it overheating or anything like that the only thing that i have noticed is that when i run it cold it will stutter and stall if i try to drive right away but if i pull over and let it sit a second it is fine

16500
P0116
Engine Coolant Temp.Circ Range/Performance

16501
P0117
Engine Coolant Temp.Circ Low Input

16502
P0118
Engine Coolant Temp.Circ High Input

those are the only codes for coolant related stuff. The new style ect's are green and 4pin located on the coolant flange between cyl head and air box.
Coolant resivour problem usually only causes (low coolant) light to come on when car is cold. get the code again..

the obdII tells me that the code is P2181 which it says is the coolany perf.

I have seen that code. Do your coolant fans work? If not i would suspect either the coolant fan module under the battery tray is faulty or the cooling fans are faulty.

do vdubs such as my car have electric coolant fans because i know when i start the car and even let it warm up or idle that the fans do not kick on however i still have had no prolem with the car overheating at all