I would just loosen the sender til no more air came out. That said, I've never had to burp a Renix cooling system in all my days. Just ran it with teh cap off til it gulped all the water in.

 

Yep I've never burped a car, and that's the way I've always done it and never had issues.

 

I'll bet you're fine.

You'll like that factory stat.

 

Your IR gun showed it truly was hotter in the rear than front.
Shows it had a bubble or restriction in the block.

May be gone now.

I've always hated trying to burb a Renix - it's not easy to hold it over your shoulder without dropping it!