My truck does not have the check valve. At least not in the cooler line. Must be internal...

 

Three months and about 5000 miles later (including a road trip to Florida from Ohio) still no problems.

 

Good to hear... you know being an engineer for a manufacturing company, I would suggest you contact the manufacturer of that bad filter... they may compensate you to apologize for the problems you had, and so they can get the bad filter back to test out what happened...

Just a thought though...