JD 4520 rear hydraulic cylinder wont lower fully

NickGrey · May 8, 2014

I've got a John Deere 4520 with a pegasus 3 gang roller mower hooked up. First time use I can't get the third deck to lower fully. There is loads of pressure, it lifts them fully up very fast, but when I lower them the first two lower fully but the third one lowers slightly and is left hanging in the air.

Any suggestions would be welcome - the rear fluid was well over 'full' and I drained it down to full mark but it still won't lower. I would say the other two arms are longer=heavier if that is relevant

cycle_gator · May 8, 2014

Are these single or double acting cylinders? That is do they have two hoses each or only one each. If the latter I suspect it is some type of piping issue that is not allowing all the fluid to drain back. Pictures?

NickGrey · May 9, 2014

cycle_gator said:
Are these single or double acting cylinders? That is do they have two hoses each or only one each. If the latter I suspect it is some type of piping issue that is not allowing all the fluid to drain back. Pictures?

They are single acting, one hose only. I used the mower on a Massey on a 3645 and it lowered fine.

Thanks for your help

kevin37b · May 9, 2014

Are the connections to tractor completely seated ? They can look it but not be .

cycle_gator · May 9, 2014

Yes, do check the QD's, what appears to be happening is that something in the piping is causing just enough back pressure to stop the fluid from draining out of the last cylinder completely. An ill-seated QD could do that. I think we may get more help if you move this thread to the hydraulics forum. The other possibility is the way the tank return and power beyond are plumbed if this is the last valve in the circuit. If they are tee'd into a common return line there may be just enough pressure there to keep the last bit of fluid in the cylinder. I assume you are running this off a rear remote that is set up for double acting valves? The fact that it works on another machine suggests the issue is not on the mower, but in the way the hydraulics on the JD are connected. With a double acting cylinder you would be unlikely to observe the issue, unless, that is, it is simply an ill -seated QD. That seems to cause all sorts of untraceable and non-sensical issues.

NickGrey · May 9, 2014

Thanks for your help guys. It turned out that I just needed to run the tractor for a few minutes and the oil warmed up and it went down. I'll check the joints, they may need greasing or cleaning.
Thanks again for your help
Nick