Unimog Maintenance Guide: power steering Oil Change (Checklist & Torque Specs)

Draining

1. Jack up the front axle: Lift the truck until both front tires are completely off the ground.

2. Clean the reservoir cap: Before opening, wipe the reservoir lid to ensure no dirt falls into the system.

3. Extract old fluid: Use a suction pump or turkey baster to remove as much fluid as possible from the reservoir. Use clean rag to soak up remaining oil and wipe inside of reservoir clean. (This step may not be necessary)

4. Remove the filter: If your reservoir has the internal filter (held by a spring at the bottom), remove it now. I think it is just push down a bit and turn 90 degrees.

5. Remove plastic tee handle and spring from old filter – It took me forever to figure out that they just pull apart. The plastic handle is just a press fit.

6. Remove the drain plug from the steering box: Let drain (17mm socket)

Loosen or remove the return line from the steering box: Let drain. This is the bigger banjo at the bottom. (22mm socket)

Start engine for a tenth of a second: More fluid should drain

Turn the wheels: Use steering wheel and turn from stop to stop until no more fluid drains. WARNING: if you leave the cap off, the air will blow oil out of the reservoir and all over your engine bay.

Measure the fluid: Make sure you got it all (2.25 Litres/76 Ounces)

Filling

1. Install new filter: Connect a fresh filter (MB A 000 466 21 04) to the tee handle and spring. Then install in reservoir.

2. Replace drain plug: (17mm socket)
Washer: New brass crush washer (18mm x 24mm x 1.5mm)
Torque: Could not find (contact me if you know)

3. Replace return line banjo bolt: (17mm socket)
Washer: 2x new brass crush washer (18mm x 24mm x 1.5mm)
Torque: Could not find (contact me if you know)

4. Initial Fill: Fill the reservoir to the top of the filter with Red Line D4 ATF.

5. Phase 1: The Cold Bleed (Engine OFF)

• With the engine off, slowly turn the steering wheel all the way to the left, then all the way to the right.
• Repeat 20 times.
• Keep an assistant at the reservoir to top off the fluid as air bubbles out. Do not let the reservoir go dry.

6. Phase 2: The Hot Bleed (Engine ON)

• Start the engine for only 2–3 seconds, then shut it off. Top off the fluid level.
• Start the engine again and let it idle.
• Slowly turn the wheel lock-to-lock 10 times.
• Do not hold the wheel against the steering stops.

7. Final Check: Lower the truck, check for leaks at the fittings, and verify the fluid level is at “Max” on the dipstick when the oil is warm.

Technical documents and sources

Benzworld threads

https://www.benzworld.org/threads/power-steering-fluid-change-sbu.1712345/?post_id=5783207&nested_view=1#post-5783207

https://www.benzworld.org/threads/steering-box-drain-plug-won%E2%80%99t-come-out.3093683/?post_id=18377383&nested_view=1#post-18377383

Parts list