Hi all, I am new to this site, but it looks good from what i see. Im in need of some help with a Genie GS-2668 4x4 scissor lift. It will airate the hyd oil in the tank force the oil/air out of the filler cap on tank. It was fine all summer long, i noticed it doing this last winter just before it turned warm, once the warmer weather came then i had no trouble. Cold is here again and it throws out a fair amount of oil and makes quite a mess. It only seems to occur when using the drive function, and once youve warmed up the lift its ok, but first thing in the morning, not so good. I made sure i have the proper weight of oil in the tank, changed hyd filter, cut it open, no debris to speak of. I have pulled out some relief valves and whatnot looking for blown o-rings, but have come up empty handed. Serial number is GS6805-43842. Any help would be appreciated. Also i notice the brakes are not as quick to apply as some of the other lifts we have of same make and model. those have the counterbalance valve mounted at the dcv for forward and reverse drive functions, where as this unit does not. When talking to local repair shops here, buddy says those counter balance valves actually do nothing, and is a waste of money as i wanted to order them and install to see if brakes would work better. I would assume the counter balance would cause the drive motors to stay in a closed loop when joystick is returned to center and would aid in braking??? no? Thanks for any help out there.:Banghead
Welcome to HEF 240 Gordy. :drinkup That's a curious problem. I can't think of anything on the pressure side of the system that would aerate the oil, as it's under pressure on the output side of pump with not much way to ingress air. Different story on suction side of pump. I'd check the hose that connects reservoir to pump. With cold oil, a bad hose connection could easily suck air, yet not leak oil. If no problem there, you could have a bad shaft seal on the hyd pump sucking air by the shaft seal into the pump on the suction side of the pump housing. As for the brakes, I'm not familiar with that machine, but it could simply be a "ramp" adjustment for the drive system. I'd contact Genie and see if drive ramp is adjustable.
Important matters first: The braking distance for the RT2668 serial # GS6805-43842 at high-drive speed on good-traction pavement is a maximum of 5 feet. ALSO: In the aerial world, the parking brakes MUST be able to hold the machine on any grade angle the machine is able to climb.....no exceptions. Your RT2668 has a rated gradeability of 40%. This is a 4' rise in a 10' distance. Run the machine up the steepest grade available, shut down the engine and determine if the machine is creeping back down the slope. If the brake discs are worn, the machine could begin to creep back down the grade. If the machine holds solid on the slope, the discs are probably ok. If the issue is the amount of distance traveled when stopping, it must be determined if the oil is getting out of the brake assemblies fast enough. Tee a pressure gauge into the brake line between the brake-release (towing) manifold and the brake assemblies. Monitor the pressure while driving and stopping. The pressure in the brake circuit should drop almost immediately when the joystick is returned to neutral. If it doesn't, there may be a restriction downstream causing pressure to remain on the brakes. This would cause the increased stopping distance. Verify the brake release plunger in the towing manifold has not been damaged and is causing restricted flow-back from the brakes. Also verify that the brake valve assembly in the function manifold has not been damaged. A bent or distorted cartridge can cause this issue as well. The counterbalance valve addition does indeed increase the performance of the braking system but ONLY if the brake discs are in good working order. The counterbalance valves are used to restrict flow back to tank from the drive motors. This helps reduce the speed of the machine when stopping. They are set at 1500psi. If adjusted less, then they will not be of much assistance. The oil issue Is the oil foaming? This would be an indication of air getting into the hydraulic oil. A curious thing happens with the oil system during cold temperatures. We get hundreds of calls per winter season about the machine generating their own oil. Like to tick OPEC off or something. I am not assuming anyone's intelligence on this. I am adding this photo to let those of us who may not know this. It has been known to mess up many very experienced technicians. The oil in the sight glass at ambient temperature must be at the thermometer point on the sight glass. In the photo the thermometer reads 50 degrees F. This is the level the oil needs to be at when the oil and the atmosphere are at 50 degrees. If the oil level is brought up to the FULL mark when it is at a cold temperature, then for certain when the oil got up to operating temperature, oil volume will definitely exceed tank capacity.
Notice the location relationship between the filler neck and the FULL mark in the photo. There is small wonder oil will vent out the filler while driving if it is overfilled. Especially driving uphill or uneven terrain. Also note where the return line enters the tank. Visualize what is happening when going uphill with the return line submerged and the tank overfilled.
Oil level should not cause airated oil unless the return line has lost its hose that returns oil below the surface and the low winter oil is below the dump on the return. There should be some kind of fitting or hose to bring that oil below the surface so it would not airate on steep slopes also.
Hey, thanks for all the info from willie59 and especially voodoomojo, its much appreciated. I Believe i did indeed have the oil level too high in the tank, I had already brought it down to aprox level suggested by voodoo, before I even had time to check this thread to see if anyone had responded. Havent had the oil faoming trouble since. Just supprises me how sensitive this unit is where the other 2 we have dont do this, and their oil level is higher in the tank than the troubled unit. Oh well, as long as it works, I will stop messing with that issue. But............as far as the brakes go, I must do something, yes they do hold on whatever incline that the unit is capable of climbing, but only if the hill is long enough that it has time to apply the brakes and stop the unit. so when unloading off our beaver tail deckover trailer, this is difficult, as it will free wheel down the ramps and has the brakes applied only after it has leveled off. I have also done the test voodoo suggested for the braking distance of 5 feet. The machine is close. About 6 feet is the stopping distance if my reaction to let go of joystick when I pass the line is accurate. just seems as though when you add a hill in the equation then the machine goes way past the 5 foot mark. I do alot of comparing to the other 2 2668 machines we have here, neither of them behave this way when unloading. Thats what makes me think something is wrong. One of the machines is newer and the function manifold does not have the same dcv setup as the troubled unit, So i do not see the exposed counterbalance valves, but maybe they are in the system somewhere. The other older unit does have the same function manifold, which also has the counterbalance valves in it. I asked the local repair facility here which is called CSL to get me the valves in, they ordered the wrong ones and presented me with some system relief valves. there is no part number in the parts manual for them, only a reference to them. Not sure if I can add them or not. This is all very frustrating!! But once again, I have and do appreciate the help given. Thanks for your time.
Could be manual release (AH) is partially engaged. This would allow oil to flow through check valves at hand pump (AG) to release brakes, but partially engaged, or malfunctioning, manual release would restrict flow of oil back to tank to engage brakes. Could also be brake pressure dump valve (U) is remaining powered up by ECU for too long before opening and dumping brake pressure. Check the voltage going to coil (Y2) of dump valve, should have power when machine is driving, once joystick is released to stop drive, check how long power remains on wire feeding dump valve coil.
:tong Willie, do you really want to dump all that oil on the Ground?:tong
Mojo...I didn't even realize what I did until you pointed it out. Now, with this current revelation, and consumption of several adult beverages, I'm reduced to uncontrollable laughter. Bah ha ha ha hahahaha :falldownlaugh
You guys are funny, I had to look back at his symbol to catch what u were talking about, lol. Anyway, I hooked a pressure guage in line by the manual release brake valve, pressures up to 800 psi at the maximum when driving unit. and releases fairly quickly, like in about 2 seconds, when pressure hits 0 we are at a dead stop. I dunno, I'm thinking if those counterbalance valves were in place they could help slow the unit down so the brakes can finish stoping the machine, seems like when we are unloading off the trailer the motion of the rolling machine coupled with the angle we are on, which is close to the max it will climb anyway is just too much for those brakes to slow down quickly. anyone know a part number for those counterbalance valves, no number in the service manual, and parts manual doesnt even show them???:beatsme
I have to admit I'm far disconnected from this machine as I've never worked on one. But it seems, according to the schematics, that they offer machines that have "Dynamic Braking" (AB and AC) which add the counterbalance valves in the tank return lines from motors, which would help to slow the machine until brakes engage depending on what pressure the valves are set. The thing that puzzles me is you have a machine that acts more like a "slab machine"...yet it's 4WD, which is typically a machine used on rough terrain, including slopes, to which fast acting brake engaging would be desirable. I'm just baffled that they would offer a 4WD machine that would coast a bit until it stopped. Then again, I'm not the genius that builds these machines.
But hey, at least I drew the symbols for the tank lines correctly this time. :tong
I have been told by the local repair shop here that these genie 2668 scissors are nothing more than a glorified slab machine with some big aggresive tires bolted on and that the drive motors dont stand up well as a result, of course the guy that told me that is as arrogant as they come, so I'm not sure he is right. On a side note, nowhere on the serial number/ ID tag does it say RT.......could this be a slab machine that someone put 4x4 tires on?? havent seen one like that around these parts, but doesnt mean they dont exist i guess? I'm going to give another call into genie tech support and see if they can help any further. See what results from that.
But yes it does have a drive motor at all 4 wheels, so I guess that does make it an RT. Sometimes I love my job, just not today!! lol.
some information on the counterbalance valve installation: