Coolant tank not holding vacuum

[brewerbry]

I replaced the el cheapo tank with a genuine Porsche tank from Pelican and guess what - it now holds a vacuum. I admit I vacuum tested the new tank before installing it and it was good.

The bad tank had aflaw in it by the overflow relief that kept it from ever sealing, the injection molded plastic did not travel to the far ends of the mold.

Lesson learned!