Massey Ferguson 0A.42.21: External Hydraulic Valve 4 Issue

Malfunction, sticking spool, or electrical connection problem within the circuit of the 4th external hydraulic remote valve (spool valve).

• 7724S
• 5712SL
• 7722
• 7722S
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 7726S
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• 4707
• 4708
• 4709
• 4710
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626

1. 1

   Check the UTTO (Universal Tractor Transmission Oil) hydraulic fluid level and condition, and inspect hydraulic filters for blockages or contamination

2. 2

   Inspect the wiring harness and electrical connector at Valve 4 for corrosion, damage, or loose pins

3. 3

   Check for faulty or non-matching hydraulic couplers, damaged O-rings, and external leaks around the valve block

4. 4

   Test the relief valve pressure with a pressure gauge and check if the spool is physically sticking

1. 1

   Preparation

   Turn off the tractor, lower all implements to the ground, and relieve all hydraulic system pressure.

2. 2

   Locate the Valve

   Locate the external hydraulic valve stack (typically mounted on the lift cover or rear remote assembly).

3. 3

   Disconnect

   Disconnect the electrical harness connector from Valve 4. Remove the hydraulic hoses and lines connected to the valve.

4. 4

   Removal

   Remove the securing bolts holding Valve 4 to the base plate or manifold. Carefully separate the valve from the base section, ensuring you do not drop debris into the hydraulic pump or lift cover.

5. 5

   Rebuild or Replace

   If the spool is sticking or leaking internally, rebuild the valve using an OEM spool valve repair kit (replacing all internal seals and O-rings). If the electronic solenoid or valve body is heavily scored/damaged, replace the entire valve assembly.

6. 6

   Reinstallation

   Smear the mating surfaces with the recommended sealant (e.g., Loctite 510) or install new base O-rings. Bolt the valve back onto the base plate and torque to OEM specifications.

7. 7

   Reassembly

   Reconnect the hydraulic lines and the electrical harness.

8. 8

   Testing

   Top up the UTTO hydraulic fluid, start the tractor to warm the oil, and test the valve's operation. Clear the 0A.42.21 DTC using your diagnostic tool.