John Deere 1020 with poor hydraulic pressure

[snowman69]

The high pressure pump looks like it has two inlet lines. I want to check the pressure coming to it. I think the pump in the back of the tractor is weak as it takes a little bit for pressure to build and it drops or looses pressure when using my bucket.

 

[buickanddeere]

The 2nd "Inlet line is two way. Surplus oil travels up into the cooler and reservoir then to the transmission when the front pump demand is low. During high demand from the front pump when the trans pump can't keep up. Oil flows by gravity to the front pump from the cooler and reservoir.
If the loader returns oil direct to sump via the scv instead of to a ported filter cover.Continuous high demand hydraulic loads on Dubuque/Mannhiem utility tractor leave much to be desired.
It's time to get a pressure gauge and measure transmission pump pressure at the ports. Then test flow up to the front pump.
Would not be the first time the wrong oil in the transmission ruined the brakes and plugged everything. If the trans filter plugs with dirt or ice crystals. The divert valve can hammer and break internal lines inside the trans. More than once an errant o'ring form the trans filter has been found inside a transmission valve.
If you look in the parts book. At least one transmission internal oil control valve is accessible form the side of the tractor. Should be checked for free travel and no broken parts.

 

[Tx Jim]

Trying to check trans pump pressure on a 1020 can be difficult at best. If tractor has SCV stand-by pressure can be checked there by simply plugging gauge in to breakaway coupler and activating lever. How long since hyd filer was changed and sump screen(parts key #30) checked/cleaned??? hyd filter relief valve b&d mentioned is parts keys #24 & #27

 

[snowman69]

Trying to check trans pump pressure on a 1020 can be difficult at best. If tractor has SCV stand-by pressure can be checked there by simply plugging gauge in to breakaway coupler and activating lever. How long since hyd filer was changed and sump screen(parts key #30) checked/cleaned??? hyd filter relief valve b&d mentioned is parts keys #24 & #27

Thanks for the reply. This has been an ongoing problem. changing the filter and checking the valve did not help. It has JD fluid in it. With no use of hydraulics it has 1800 lbs pressure. Drops to nothing when you open a valve or under 500. If not a valve problem I think it is the pump (primary?) inside the tractor. I have a gauge by my controls.

 

[snowman69]

This pump has 3 lines. two about 3/4" which must both be return and the one that is 1/2 should be the pressure to it.
The fluid is good (JD) and the filter has been done and I cleaned some junk out of the valve earlier. This has been an ongoing problem I want to get fixed.

 

[Tx Jim]

Exactly what control is gauge installed by?

Have you cleaned sump screen(parts key #30)?

Does your tractor have open center power steering IE does it have a pump bolted to frt of engine?

How is loader controlled(ind valve or scv)?

 

[J_J]

Your hyd system appears to be a closed center hyd system, and will probably have a standby pressure.

What is the function of the spool you are operating.

A hyd component will only develop pressure when it is doing work.

If the fluid is bypassing to tank, you will see little pressure.

Put the gage in front of the component. If the component is good, and the pump is good, then the valve is the problem.

Does your 3pt work.

Hydraulics:
Type: closed center
Capacity: 10 gal [37.9 L]
Pump flow: 10.5 gpm [39.7 lpm]

 

[buickanddeere]

Your hyd system appears to be a closed center hyd system, and will probably have a standby pressure.

A hyd component will only develop pressure when it is doing work.

Hydraulics:
Type: closed center
Capacity: 10 gal [37.9 L]
Pump flow: 10.5 gpm [39.7 lpm]

The system is closed center and when at rest is supposed to have 2250psi in the pressure lines and dead headed against the loader, PS, SCV and rockshaft control valves. The variable displacement pump will be running with little to no flow.
Anything anywhere flowing oil on the high pressure side when no loads are being operated is a problem.

 

[J_J]

I would suggest to put a hyd pressure gage in the system and check to see if the pump is still capable of making that pressure.

Your relief need may need to be reset.

 

[snowman69]

Gauge is installed right before axillary controls for bucket. It made no difference when I changed filter. The power steering is fed off of line to front high pressure pump. The gauge reads 1800 when nothing is being used but goes down fast when control valve is opened, sometimes to zero.

 

[J_J]

What is the control valve controlling?

 

[buickanddeere]

I would suggest to put a hyd pressure gage in the system and check to see if the pump is still capable of making that pressure.

Your relief need may need to be reset.

There is no relief valve on the closed center pump. There is a stroke control valve that de-strokes the pump when system pressure reaches 2250psi.

 

[buickanddeere]

You need to verify there is no high pressure oil if flowing when the PS, rockshaft, scv and loader is not being used.
Oil pressure is low either because of a high pressure side leak or low flow from the trans pump to supply the front pump. Or the stroke control valve spring is weak and/or the valve/seat is worn. Dial the standby pressure up to 2300psi.
There is a priority valve that stops oil flow back to the scv,rockshaft and loader if properly plumbed. To preserve operation of the power steering if there is a partial hydraulic system failure.
Front pumps do eventually wear out or break but.....................they are replaced as a wild guess probably 100 times too often. Instead of solving every high pressure leak or low supply flow from the trans pump.

 

[snowman69]

The loader cylinders and bucket.

 

[J_J]

So you are saying the system can build up pressure, but the loader can not develop the pressure or the flow is going somewhere else.

Have you checked the cyl for proper operation. Try connecting the cyl to another source/pump/tractor and see if they can develop the advertised pressure.

If the cyl are known good cyl, then the loader valve is bad.

 

[snowman69]

I will check the PS and rocker this week. I am going to hook up a gauge to the line and see what it is doing. I do not know where the adjustment for the standby pressure is. I plan on trying to find a service manual to look at this week.

 

[Tx Jim]

snowman69
HAVE YOU CHECKED/CLEANED SUMP SCREEN??????????? You keep answering you've changed hyd filter but a clean sump screen is just as important to the operation of this tractors hyd system as the hyd filter. Is your tractors serial number within or """above""" this range(010001-045199)?? The SN is on RH side of trans case under the seat. Have you tried tightening stroke control valve to increase stand-by pressure to the factory setting of 2250 psi?

 

[Tx Jim]

I do not know where the adjustment for the standby pressure is. .

Parts key #29 CW to raise pressure.