Proper hydraulic motor operation to reduce motor or seal failure


Hydraulic motor and/or motor seal failure

Situation or Problem

Improper connection or operation on John Deere or competitive tractors can result in a hydraulic motor or seal failure.


Proper hydraulic motor circuit connections and operation can greatly impact hydraulic motor integrity.

Solution Steps

John Deere air seeding and planter hydraulically driven motors must be properly connected to the tractor and correctly operated to minimize damage to the motor and/or seal.

NOTE: Always refer to the appropriate Operator's Manual for specific connection and operating information.

Use the following as general guidelines when connecting and operating hydraulic motors that are on a separate tractor SCV.

Connecting the Motor Circuit to the Tractor:

1. Connect the flow going to the hydraulic motor to the retract side of the tractor SCV.

- Refer to the following illustrations as examples of a John Deere and competitive tractor:

Retract side of SCV - John Deere
Retract side of SCV - competitor

- Connecting the circuit in this manner ensures the tractor SCV must be operated in the lower mode to run the hydraulic motor.

2. Connect the flow returning from the hydraulic motor to the tractor motor return port (if equipped).

Motor return port - John Deere
Motor return port - competitor

The tractor motor return circuit is designed for flow and can significantly lower the back pressure of the return side of the motor circuit versus directing return flow through the motor circuit SCV (if a motor return port is not available). Since the hydraulic motor seal may be exposed to the motor return flow, the lower back pressure of the motor return circuit can be beneficial to motor seal integrity.

Hydraulic motor return couplers are typically opened when coupled (do not require reverse flow to open).

3. Connect the case drain line to the case drain tractor coupler.

Refer to the following illustrations as examples of a John Deere and competitive tractor:

NOTE: Case drain port coupler not shown on John Deere tractor photo.

Case drain port - John Deere
Case drain port - competitor

- Always connect the case drain circuit BEFORE operating the motor.

- The case drain circuit is designed for leakage only (minimal flow at low pressure).

- The tractor case drain circuit must be less than 25 psi to prevent hydraulic motor seal damage.

- The case drain circuit is not designed for motor return flow.

- As of May 2004, John Deere  planting and air seeding equipment are equipped with a flush-face type case drain coupler. The unique male hose tip is unable to connect in to the prior type female case drain coupler body on the tractor.

- If the tractor case drain circuit is equipped with a hydraulic filter, refer to the appropriate tractor Operator's Manual for servicing requirements.

4. For John Deere  30-60 Series Tractors equipped with mechanically actuated SCVs:

Verify the rubber stop is installed on the slot of the fan SCV to keep the lever from returning to neutral.  Refer to the appropriate tractor Operator's Manual for more information.

Operating the Motor Circuit:

With the tractor running:

1. Position the SCV lever to the lower position to activate the motor circuit.

2. Adjust the appropriate tractor SCV flow control until the desired motor operation is obtained.

3. Position the SCV lever to the float position to shut off the motor circuit.

- Positioning the lever to float allows the motor to coast down to a stop.

- Moving lever to neutral can cause the motor to stop abruptly and may damage the motor or motor seal. Even though most motor circuits include either an internal or external bypass circuit, using neutral to stop the motor is not the preferred method to stop the motor.

- If the tractor is equipped with electrohydraulic SCVs, allow the motor to coast down to a stop prior to shutting off the tractor. Loss of hydraulic pressure from the tractor will return the tractor SCV to the neutral position.

- Some John Deere  and competitive tractors have a hydraulic motor operating mode that limits motor operation to the lower and float positions. Refer to the appropriate tractor Operator's Manual for more information.

Affected Equipment
1900      1910   
1700      1710   
1720      1730   
1750      1760   
1760NT      1770   
1770NT      1780   
1790      DB Planters   

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