The valve on the bottom of the ram- has that been inspected?
No, individual lines to each cylinder, pulled the free lift cylinder and inspected. Found the piston seal and back up rings improperly installed. Corrected this but the problem still occurs. Pulled the check valve and inspected. It was free and clear of obstructions. I'm out of ideas for this problem, guess that is why it has been going on for three years before I got it.
Does that have a hydraulic pipe going from the top of the shaft of the right side rear lift cylinder down to the free lift cylinder? That right side cylinder is different from the left in that it has a piston on the bottom of the shaft. I'm thinking that could cause a problem with the flow to/from the free lift cylinder.
You have 60 other lifts- are there any other lifts that match this one? Have you swapped an operating safety valve into this lift & installed this valve into a working unit?
Only the free lift cylinder is hanging up, the rear cylinders both come down normally. Once the truck warms to above freezing temps the free lift comes down normally. This is one of 60 freezer trucks we have and the only one exibiting this problem.
If it's like the gas models, they have a solenoid valve on the control valve to prevent lowering unless it is running and on the seat. Do you have to have the key and seat switch on to let the forks down? If so, maybe that valve is malfunctioning.
Yes, the safety valve is located in the manifold that t's to the cylinders.
When you say"loosen the safety valve"- what exactly are you describing?
Is the safety valve the block on the back of the upright which T's the hydraulic fluid to the 3 hoist cyl's?
I tried another safety valve, did not help the situation. All pressures have been set to specifications. I am about out of ideas for this particular problem. Do not think it is a binding problem in the cylinder since I can open the line and the cylinder drops normally. I noticed someone has replaced the load sensor(in the same block as the safety valve). I have never seen one of these cause this. The lift valve is working normally. Any ideas out there?
If you suspect the safety valve is defective i'd be tempted just to fit a new one.
I've had this happen on other (non-forklift) equipment. If the safety valve is suspect, I'd remove it, mic all the clearances while warm, then allow the valve to sit in the cold environment over night & mic again while cold.