Oil leak under panel?

Flew my coupe the second time since replacing the engine and wings. This time I flew for twenty minutes. Flew great! When I landed, shut her down, I felt something hot on my left leg. Looked down & from my knee down, was oil soaked! Slid her in the hanger and proceeded to look for the leak. Looks like the temperature gauge? Not understanding this set up. How can the oil line just go into the gauge without putting pressure there? Should it be like a " round robin"? Should it build pressure? Thanks in advance for any insight on this subject.