The platform level on our Genie Z60/34 keeps settling and it has finally reached the point wher it will lift itself but not an operator. We are starting with the assumption that the platform lift cylinder is leaking internally. But we wondered if anyone has has a similar problem and if so what caused it. Thanks
Welcome to the forum Despete51. :drinkup What is the machines serial number? Are you talking about the main boom lift cylinder, or the platform leveling cylinder?
It is the platform leveling cylinder. However, we disconnected the hoses and capped the fittings on the cylinder and the platfrom no longer settles, so I guess that rules out the cylinder. Now I wonder if it is in the leveling system. I am not quiet sure how that works. I will have to find the serial number. Thanks
Does anybody know where to find the serial number on this?
On the side of the machine where the ground control panel is, lift the door and you should see a sticker either on the panel or attached to the bulkhead of the machine. On the same side of the machine, it should also be stamped into the metal just below the rotax gear/turntable
The serial # is 911.
When the primary boom is raising, does the platform stay level throughout the raising process? Does the platform remain level all the way through the boom lowering process? The machine uses a master-slave system to keep the platform level throughout the boom raising / lowering functions. The Master cylinder (C) is pinned on the upper pivot assembly near the pivot end of the primary boom. The other end of the Master cylinder is pinned to the primary boom. As the primary boom is raised, the rod end of the Master cylinder is pulled out from the act of the primary raising. The oil in the rod end of the master cylinder is forced to travel to the Slave cylinder (E). Here it will manipulate the counterbalance valves on the Slave cylinder and force the cylinder to retract. Counterbalance Valve (B) is in the circuit to ensure the oil goes to the slave cylinder and not through the function manifold back to tank. If the Platform remains level throughout the range of motion of the primary boom up/down, then the condition of the Counterbalance Valve and the Master Cylinder should not be suspect. If the platform does not stay level during boom up and down, then it is possible that the oil is bypassing in the master cylinder or the function manifold. Bad packings in the master cylinder, a swell in the master cylinder barrel, trash/bad o-ring on the counterbalance valve, or a crack in the function manifold itself. When the toggle switch for platform level is used, Valve A opens, letting oil into the circuit. If there is bypass in one of the mentioned components, then you will experience the results you are having.
Just thought I'd add: before you remove counterbalance valves in function manifold or the ones at slave cylinder, make sure booms are fully down at rest and raise front of platform with a floor jack just enough to relieve pressure on slave cylinder.
Also, NEVER attempt to "adjust" a counterbalance valve. They are a Safety component and must be replaced if tampered with or evidence of having been tampered with is discovered. Serious injury and even death has been the result of improper handling of counterbalance valves. As Mike Smith of JLG always says: "They are the easiest valves in the world to adjust. Just throw them away and install new ones." They are preset at the valve manufacturer's facility.
The problem has gotten worse. It will no longer adjust the platform with the weight of an operator. Switching the hoses causes it to work when you work the switch backward. If one counterbalance valve was bad, would that affect the pressure on one side of the circuit?
Does this mean that after switching the hoses the platform will lift a man when the switch is pressed in the down direction? Where were the hoses switched at? the Slave Cylinder or the Function Manifold? yes but it depends on which counterbalance valve we are talking about. please answer these questions: Where did you switch the hoses at to achieve your results? When the hoses are in the original locations, does the Platform self level when the Primary Boom is raised and lowered? this is important information. This condition is usually remedied after a 10 minute diagnosis.
The hoses were switched at the slave cylinder and the platform does self level when the primary boom is raised and lowered. Of course it works backward when the hoses are switched. Yes it will raise a man on the platform with the hoses switched.
we are almost there! Place the hoses on the Slave Cylinder back to their original locations. At the Function Manifold, swap the hoses marked PL1 and PL2 with each other. (not P1 and P2) If the Platform Level does NOT raise Up while selecting Platform Level Down, then the problem is in the Master Cylinder. If the Platform Level does raise up while selecting Platform Level Down, then the problem is in the Function Manifold or one of the Counterbalance Valves in the Function Manifold. If this is the case, swap the two counterbalance valves in the manifond to see if the problem follows the valve or stays with the PL1 port. If it follows the valve, inspect for debris or damaged o-rings or replace the counterbalance valves. If it stays with the PL1 port then the manifold could be fractured
This is what was installed when serial number 911 left the factory. When a machine is approaching 20 years of age, many things may have been changed from repairs or upgrading. If what is drawn here does not match your machine, let me know. I can give you my phone number and we can discuss.
When we reversed the hoses the platform raised extremely slowly, but still will not move with any weight on it. Also the platform still settles with the hose reversed. I assume that means we should rebuild the master cylinder, is that correct?
It would appear to be. There is a test to verify the master cylinder is faulty if you have caps and plugs to do it. If the platform level performs correctly when using the toggle switch with the master level cylinder bypassed as in the drawing, then yes, the master cylinder needs repair. Of course, with the master cylinder bypassed, the platform will not self-level when the primary boom is raised or lowered. One important note: Check the master cylinder bore for out of round or size nonconformity. An inside-diameter micrometer or bore gauge will help. The barrel of the master cylinder may be distorted. Buldged is perhaps a more appropriate word. If someone at sometime has jacked-up the manifold or slave counterbalance valves, then the pressure exerted by the master cylinder (when raising or lowering the primary boom) will not be able to open a respective counterbalance valve. Being that oil cannot be compressed, it has to go somewhere. The cylinder barrel is the weak link in this case and will buldge. Sometimes been known to burst...it can get very ugly! We always suggest replacing the counterbalance valves when their state is unknown.
Under no circumstance operate boom up/down if the master level cylinder's ports are capped off. If there was no master cylinder damage beforehand, there certainly will be afterward. I meant to edit that into the last thread entry but was too late.
Would not be pretty.
Sorry, I have been busy with other problems. Just got the lift back in the shop today and the troucle appears to be the master cylinder. Thank you very much for all the help.