I just had to replace a hand wheel pinion on my newly acquired 14" Logan and after putting it back together and filling it with oil I'm getting quite a bit of leakage. This is a two-piece, front/back, style casting so it has a seam across the bottom.
So it's a machined metal, non gasketed joint, that is designed to hold oil? I'm going with that, if I'm wrong, stop reading because I'm out in left field...
I cleaned the surfaces where they meet pretty carefully,
Cleaned them how? Specifically, were there any abrasives involved?
and tightened the bolts holding them together more than enough when I reassembled,
How tight is more than enough. This can be a problem, as a machined joint that seals dry will have a fairly low clamping force. Well, prior to cost effective mass production with 3D CNC machining at 50 millionths of an inch anyhow.
but it's leaving a puddle overnight. Honestly, I think I cleaned the surfaces too well because there was some dried stuff there that was probably acting as a gasket.
You're positive it was not a pre-existing sealant that might be called out in a manual somewhere?
Has anyone used something like High-Tack gasket sealant without a gasket for a situation like this? Maybe something else?
I never was a fan of that stuff. I've used plenty of it,
Loctite 515 or a direct cross reference would be my first choice. Flange Sealant or Gasket Eliminator are two common names if you cross it. It does "harden", but not what you're worried about. It stays flexible in lighter castings, and it'll come apart pretty reasonably in future services. It's not reusable, but It's an anaerobic sealer, so it won't dry in the tube, one tube will last a lifetime. You're just fighting gravity, right? No pressure on that oil? If that's the case, no setup time is required, you can bolt it together and fill it up. You still want reasonable to light torque on the fasteners responsible for the joint. Cranking down on them will start to pull apart the sectons between them, and open a gap.