The ETCS also sends information to the computer...so if the pcm is not getting the correct information it's not sending out the correct information. Replace both and get them fro you local GM dealer.

+3.....but we seem to be overlooking the

>>>>
I need to add coolant to it now weekly
>>>

I agree ECTS replacement will help but if it's not boiling over and there is no detectable leak, the coolant is going somewhere..... might there be a chance of a slight head gasket issue (if there REALLY is no leak from anywhere else (emphasis on REALLY not leaking from anywhere else)

Wasn't there a fella on here recently who had a similar problem? As I recall, he finally found the leak from a fitting behind the engine, and the coolant was dropping onto the exhaust pipe and evaporating. Somebody guide me here .....

True True True -- hence my REALLY qualified statement

Where was his leak?
 

Where was this leak, was it a freeze plug or the heater-core? I hear and smell what I claim is a dripping leak onto the manifold/exhaust with a tissss, tissss, tisss... dripping sound after I turn off the engine when hot but 3 master mechanics from two different shops claim the noise is just expanding metal parts cooling and contracting after getting hot. I was certain the sound and smell was a dripping leak behind the engine with because of the dripping sound and smell but after the 3rd "master mechanic" told me this sound was not a dripping leak I had to dismiss it. I did try a stop leak product which seemed to not stop this sound or solve the issues. A liquid dripping sound sizzling on something hot is a distinct sound and could not understand why they did not hear this as I did... This noise happens EVERY time the motor is hot and hard to hear while the motor is running but how could these parts start to make such a noise by cooling everytime the very second I turn the motor off????

The good news is today I have an appointment to get a pressure test for 30$ and see if I need to flush the coolant system including the engine area which will cost $89 if needed. This is at 2pm EST.

If you could let me know where this leak was before 2pm that would be great???!!! THANKS So Much!!!

Thanks to everyone here for your help, I hope that I will know what is going on today and hope that you all you guys helped me to save the $300 for a new water pump!!!

link to other dude's leak