Playing 5 handed.
UTG (190) is unknown to me, but seems passive.
CO (637)is the reason I am at the table. He is a pure maniac. Playing 65/44. And often massively overpushing the pot on turn and river, but hasn't been called yet.

UTG limps. CO raises to 15 - as usual.

I have with 360 behind, and 3 bet to 35. Basically to isolate maniac.
But both call.

Flop (105]
Checked to me, I bet 77, they both call.

Turn (335)
Checked to me. I dont know what to do. I figured it made it less likely that one of them had the K so a good card. I have 255 left

I ended up making a stupid total donkish bet of 78 to put CO all in. Both called.

River (573)
Checked to me, I check behind.

Is turn a push?

I don't know...if he can fold JJ-QQ, then it's a fold, but he's never folding a K or an underful...and he may have merely had the FD, so he's not calling a bet anyway...I think checking is totally fine on the river.

Turn: I don't mind a check-behind to induce a billion bluffs from the FDs trying to rep the K.