If you have read my Volkswagen Passat B5.5 project page, you will know where I am at in this project: sorting out the coolant leak and overheating issue.
This is a common component failure point with this model and year Volkswagen. Lucky for me the engine is out so removing the flange will take no time.
My first thought after having no success with tightening the bolts was to replace the flange with a new one. Considering the unknown structural integrity of the plastic. After a quick internet search for replacement parts, I found that there was an upgraded aluminum version available from UroTuning for around $40 dollars.
So needless to say I purchased it. The quality is what I would expect from cast aluminum and was identical to the factory original. The flange also came with all the replacement O-rings.
I am confident that the aluminum version is a permanent fix.