Community
In your main assembly, set your selection mode to part priority, or find just the valve in your browser and select. Right click and select iproperties, change the appearance.
What you can also do is set up a couple of new view representations, and have the part transparent in 1 and solid in another.
I think the issue you are experiencing is to do with the association type between the sub-assemblies and the main assembly. Right click on your sub-assembly and select representations and play around.
@hoss1059 wrote:
... The model has an imported bypass valve which shows up translucent.
........
Can you zip and attach the original file here?
Sounds like a surface body that needs to be solidified.