Does anyone have an idea what would cause a loud humming noise when the elevator moves up, coming from inside the tank of a TKE Tac32 Endura (MRL) elevator? There is no noise coming when the elevator goes downwards. On the way up, its a really loud hum noise during the up run. It's definitely coming from inside the tank. There is a short between the down valve inside the access panel on the 2nd floor and the tank, but that isn't stopping the elevator from working. The elevator can operate both up and down, at the correct speed, but the loud hum noise has caused us to shut the cab down currently. If it was a pump issue or a motor issue, I figured it would not run at normal speeds, but it runs correctly. Any help would be appreciated.

Inside the tank we have solenoid valves and the pump motor. It could be either one of the UP solenoid valves or the pump motor.

Could be the hydraulic piping connections within the tank. Check where the piping exits the side of the tank. Forced fit connections can transmit noise. There should be a rubber isolation ring there to avoid metal to metal contact. Other than that, the valve stem to the pump could be loose or a rag covering part of the pump intake screen could cause this type of noise. Either way, the oil would need to be transferred out of the tank to inspect.