Quote Originally Posted by wstefan20 View Post
Not according to the GM dealer tech that I talked to, or the factory service manual I have right in front of me...

Makes sense why not with the engine running. The bubbles are going to be pumped straight past the orifice and back into the system
Regardless of what the tech or the GM manual says W body/3800 folks have been doing it this way for years...it's what works! Bubbles are going to travel to the highest point which is straight out the bleeder on the t stat housing when the t stat is OPEN with engine RUNNING at temp...that's what makes sense