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Bobcat 743 lift arm drift
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<blockquote data-quote="Tazza" data-source="post: 3423" data-attributes="member: 82"><p>As for the load checks not having an effect, my old 731 would creep down constantly, i re-sealed both cylinders and made no difference. I pulled the vavle bank out as the spools were leaking, i replaced all the seals, including the load checks and theat fixed the problems. The seals were shredded, most were hard and brittle and others were in 2 pieces. These were not the bobcat branded valves though, they were a gresson valve bank.</p><p>Ken, here is the article about cylinder creep:</p><p>***************************</p><p>[FONT=Arial, Helvetica, sans-serif]<span style="font-size: 10px">One of our readers wrote to me recently about the following problem: </span></p><p> <span style="font-size: 10px">" I am having problems with the boom on my crane creeping down. How do I determine if it's the valve or cylinder that's leaking?" </span></p><p><span style="font-size: 10px">A popular misconception about hydraulic cylinders is that if the piston seal is leaking, the cylinder can creep down. Fact is, if the piston seal is completely removed from a double-acting cylinder, the cylinder is completely filled with oil and the ports are plugged, the cylinder will hold its load indefinitely - unless the rod-seal leaks. What happens under these conditions - due to the unequal volume either side of the piston, is fluid pressure equalizes and the cylinder becomes hydraulically locked. Once this occurs, the only way the cylinder can move is if fluid escapes from the cylinder via the rod seal or its ports.</span>[/FONT]</p><p>***************************</p><p>From what you say, that it stops moving when you push the pedal far enough to get it to raise that sounds exactly like what mine used to do with bad load checks. If you push it rite down and the rams stop moving that confirms its not your rams leaking.</p><p>As for seals for the control block, i paid about $15 from a hydraulic seal shop for mine, but i do recommend buying toe correct ones from Bobcat. You will need genuine rubber boots to cover the spool rods. They are only cheap and keep the dirt out.</p><p>The spools don't have seals as such, they use 1 quad ring either end of the rod. I think this area is only low pressure too, as there really isn't alot holding them in place.</p><p>As for the big switch, its for lights, i'm not too sure what they all do, but how i wired mine up was one click wwould turn the back lighting ont he gauges, 2 would turn the front lights on and 3 would turn on front and rear lights.</p></blockquote><p></p>
[QUOTE="Tazza, post: 3423, member: 82"] As for the load checks not having an effect, my old 731 would creep down constantly, i re-sealed both cylinders and made no difference. I pulled the vavle bank out as the spools were leaking, i replaced all the seals, including the load checks and theat fixed the problems. The seals were shredded, most were hard and brittle and others were in 2 pieces. These were not the bobcat branded valves though, they were a gresson valve bank. Ken, here is the article about cylinder creep: *************************** [FONT=Arial, Helvetica, sans-serif][SIZE=2]One of our readers wrote to me recently about the following problem: " I am having problems with the boom on my crane creeping down. How do I determine if it's the valve or cylinder that's leaking?" A popular misconception about hydraulic cylinders is that if the piston seal is leaking, the cylinder can creep down. Fact is, if the piston seal is completely removed from a double-acting cylinder, the cylinder is completely filled with oil and the ports are plugged, the cylinder will hold its load indefinitely - unless the rod-seal leaks. What happens under these conditions - due to the unequal volume either side of the piston, is fluid pressure equalizes and the cylinder becomes hydraulically locked. Once this occurs, the only way the cylinder can move is if fluid escapes from the cylinder via the rod seal or its ports.[/SIZE][/FONT] *************************** From what you say, that it stops moving when you push the pedal far enough to get it to raise that sounds exactly like what mine used to do with bad load checks. If you push it rite down and the rams stop moving that confirms its not your rams leaking. As for seals for the control block, i paid about $15 from a hydraulic seal shop for mine, but i do recommend buying toe correct ones from Bobcat. You will need genuine rubber boots to cover the spool rods. They are only cheap and keep the dirt out. The spools don't have seals as such, they use 1 quad ring either end of the rod. I think this area is only low pressure too, as there really isn't alot holding them in place. As for the big switch, its for lights, i'm not too sure what they all do, but how i wired mine up was one click wwould turn the back lighting ont he gauges, 2 would turn the front lights on and 3 would turn on front and rear lights. [/QUOTE]
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Bobcat 743 lift arm drift
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