Here’s the recent pic on a non leaker (above). Note the elevated ring around the hole. That’s what’s providing a seal…no gasket required.They could make a tight fit in the end cap hole and do away with the protrusions in the hole. If the parts in hole were conical it would seal well almost like a compression fitting.
The other pics are from same area on FE and it’s FLAT, allowing minute spaces under the bypass. If you zoom in on the first one, you can even see the rough border there as well, preventing tight contact. The second one is actually from another FE, which is also rough with some debris as well,
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