7520 Hydraulic problem

[daycab]

My 7520 hydraulics will not work when the tractor is initially started. Neither the loader or the lift arms move. This is sporadic and is more likely to happen when the tractor is cold although the hydraulics have stopped working after the tractor has been run for several hours and then restarted. Sometimes cracking the pressure relief valve on the loader spool helps, but not always. Is this a stuck pressure relief valve and if so, how do I unstick it? I can find no mention in the manual or online about bleeding the system. Is there a bleeder valve on the 7520? Thank you.

 

[SPYDERLK]

My 7520 hydraulics will not work when the tractor is initially started. Neither the loader or the lift arms move. This is sporadic and is more likely to happen when the tractor is cold although the hydraulics have stopped working after the tractor has been run for several hours and then restarted. Sometimes cracking the pressure relief valve on the loader spool helps, but not always. Is this a stuck pressure relief valve and if so, how do I unstick it? I can find no mention in the manual or online about bleeding the system. Is there a bleeder valve on the 7520? Thank you.

If the relief valve were stuck you would have no, or extremely weak hydraulics. - Also, the system is self bleeding/priming so should need no help there.

A few questions:
,,,Is the system full of hyd fluid?
,,,Does it operate normally in daily use?
,,,When you encounter trouble after starting, does the hyd system (after whatever delay) come to normal function instantly - or is it sluggish or jerky for a short time before it is OK?
,,,Does full RPM aid in getting the system to resume operation?
,,,What hrs on tractor - did you buy it new?
,,,Have you changed the main hydraulic filter.

I suspect that there is a suction leak in your line from reservoir to pump. Theres a bunch of unprotected stuf underneath that is pretty sensitive to large debris.
larry

 

[SPYDERLK]

Maybe Iv made a mistake. - You show JD ownership. ... Are we talking JD 7520 or Mahindra 7520?

 

[daycab]

Maybe Iv made a mistake. - You show JD ownership. ... Are we talking JD 7520 or Mahindra 7520?

The tractor in question is a Mahindra 7520. I did buy it new, and it has just over 700 hours on it. When the hydraulics 'come to life' they are jerky initially, but operate normally after 15-20 seconds. Fluid level is good. The tractor is no longer used daily, it is not unusual for it to sit three weeks or more between uses. Blipping the throttle does help restore hydraulic operation, although it is not always effective. The hydraulic filter has been changed twice, the problem coincidentally started happening after a filter change. I thought perhaps the seal was bad on the first filter, so I replaced it again. No change. I did fill the filter with fluid before spinning it on. I'll crawl under the tractor next weekend and see if I see anything obviously damaged. Thank you for your help with this frustrating problem.

 

[Jabonee]

Suction screen clogged?:confused3:

 

[SPYDERLK]

The tractor in question is a Mahindra 7520. I did buy it new, and it has just over 700 hours on it. When the hydraulics 'come to life' they are jerky initially, but operate normally after 15-20 seconds. Fluid level is good. The tractor is no longer used daily, it is not unusual for it to sit three weeks or more between uses. Blipping the throttle does help restore hydraulic operation, although it is not always effective. The hydraulic filter has been changed twice, the problem coincidentally started happening after a filter change. I thought perhaps the seal was bad on the first filter, so I replaced it again. No change. I did fill the filter with fluid before spinning it on. I'll crawl under the tractor next weekend and see if I see anything obviously damaged. Thank you for your help with this frustrating problem.

Suction screen clogged?:confused3:

Could be part of it, but from the symptoms OP has a suction leak somewhere. Theres some joint not sealing in the suction line ... and there are lots of them. Added restriction from a partially clogged screen would sure worsen the symptoms. daycab, have you cleaned this screen? - Its in a tubular appendage bolted beside/under the rear axle. I took the screen out of mine after the 1st fluid change because they are restrictive even when clean.

Good luck finding the leak. When you fix it youll notice the loader is faster.:thumbsup:

 

[bindian]

Suction screen clogged?:confused3:

It could be clogged. My dealer told me he has seen them collapsed. Mine take a couple of seconds to respond when it is cold outside.
hugs, Brandi

 

[Jabonee]

Any signs of foamed hyd oil? Its been my experience if there is a suction leak it foams up the hyd oil.

 

[DavesTractor]

There is a small section of rubber hose on the return line or suction line from the reservoir to the pump. It has clamps. Double the clamps and tighten then up a bunch. Problem should go away. They will suck air at that location sometimes and yet not leak oil. It's not common, but we have seen it and have fixed it with that simple solution. If you happen to have the oil drained, then I'd slide the rubber coupler/hose back, clean the pipe, then double the clamps.

The other ideas about the suction screen being clogged are valid possibilities as well. The 7520 has a pretty good size pump, pulling 17 GPM through that smallish pipe creates quite a suction. If air can get in, it will.

 

[klemt]

Hi all, I'm experiencing a similar problem on my 7520 and with no service manual I'm hoping someone can assist. I lost all hydraulics (3pt, bucket, remotes) after taking a break disking two days ago. Once I started the tractor back up and hydraulics returned, later on they went out after shutting the unit down and restarting and since then have not come back. I have verified that power steering still works.

So far what I've done:
1. Disconnected quick connects at bucket to check for flow. Nothing there
2. Changed suction filter
3. Pulled and cleaned in-line suction strainer. Found to be pretty dirty, replaced with all new fluids and still unresponsive.

I will go back to the OP's original question, where is the pressure relief in the hydraulic system located, and could be stuck open causing loss of hydraulics? The question of a manual bleeder was also asked. If so, can someone help me with its location as well?

Any other ideas that may be causing this? I will check all flex hoses on suction side and re-tighten in case it's an air issue. I appreciate yalls help.

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