Check the hose and clamps prior to the hydraulic pump. It may be pulling in air. I have never had a problem with the air being worked out of the system on a 39x Linde lift after draining oil and replacing filters. It will be worked out when the controls are operated and it is driven.
The yellow flashing light in the dash sounds like the glow plug light. When it flashes there is a fault with the engine controls or faulty wiring.
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