Steps To Reassemble Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

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The reassembly process for the Series 71 oil pump is critical to restoring its functionality, ensuring that all components are properly aligned and that clearances meet specified tolerances. Proper reassembly helps maintain optimal oil pressure and circulation, preventing issues that could impact engine performance. Below is a comprehensive guide to reassembling the oil pump, ensuring each component is fitted correctly.

1. Prepare Components for Reassembly

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Before beginning reassembly, ensure that all parts are clean, dry, and free from any debris or contaminants. Organize the components in the order they will be reinstalled to streamline the process.

• Check All Components: Perform a final inspection on gears, bushings, and housing to confirm they are free from damage and wear. This last check reduces the risk of introducing worn or damaged parts during reassembly.
• Gather Necessary Tools: Ensure you have a torque wrench, feeler gauge, shims, and any tools needed to ream bushings if applicable. Organizing tools in advance will make the reassembly process more efficient.

2. Install Bushings

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If the bushings were replaced during inspection, they need to be carefully installed and reamed to ensure proper fit and clearance for the gears.

• Position the Bushings: Insert new bushings into the pump housing, ensuring they are aligned precisely with the gear shafts.
• Ream to Specifications: Carefully ream the bushings to the manufacturer’s specified diameter for the Series 71 oil pump, as proper clearance is essential for smooth gear rotation. Ensure that the reamed bushings fit snugly, allowing the gears to rotate without excessive play or binding.
• Double-Check Alignment: After reaming, confirm that the bushings are correctly aligned to support the gears evenly. Misalignment at this stage can cause wear on both the bushings and gears over time.
  

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3. Assemble and Install the Gears

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The drive and driven gears are central to the oil pump’s operation. They must be installed carefully to ensure smooth rotation and proper alignment.

• Install the Drive Gear: Position the drive gear onto its shaft in the housing. Ensure that it seats firmly and rotates smoothly within the bushing. This gear will engage with the crankshaft to drive the pump.
• Install the Driven Gear: Place the driven gear in the housing, meshing it with the drive gear. Rotate both gears gently to confirm that they engage smoothly and without binding. Any resistance or misalignment here could indicate a bushing or gear issue that needs correction.
• Test Rotation: Once both gears are installed, test the rotation by manually turning them. They should rotate freely without catching. Smooth, unobstructed movement is essential for effective oil pressure.
  

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4. Install the Relief Valve Assembly

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The relief valve assembly is responsible for regulating oil pressure. Installing it correctly is critical for maintaining consistent oil pressure.

• Insert the Relief Valve Plunger and Spring: Place the plunger and spring into the relief valve cavity in the housing. Ensure the spring is seated properly and exerts sufficient tension against the plunger.
• Secure the Relief Valve Cap or Retaining Clip: Depending on your model, the relief valve may be secured with either a cap or a retaining clip. Install this component carefully, making sure it holds the plunger and spring in place.
• Test Plunger Movement: After installation, press the plunger to ensure it moves freely within the housing and that the spring tension returns it to its original position. If there is any sticking, disassemble and clean the plunger and housing before reinstallation.
  

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5. Check Gear Clearances and Adjust Shims

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Achieving the correct gear clearance is crucial for the oil pump to operate efficiently. Too much or too little clearance can affect oil flow and pressure.

• Measure Gear Clearances: Using a feeler gauge, measure the clearance between the gears and the housing. For the Series 71 engine, the recommended gear clearance is between 0.005 and 0.012 inches.
• Adjust Clearance with Shims: If the clearance falls outside the specified range, adjust it by adding or removing shims beneath the oil pump’s mounting feet. Adding or removing a 0.005-inch shim will alter the clearance by approximately 0.0035 inches. Adjust until the clearance falls within the specified range to ensure optimal oil flow.
• Re-Check Clearance: After adjusting shims, re-measure the clearance with a feeler gauge to confirm that it meets the specification. Proper clearance ensures that the pump operates efficiently without excess wear on the gears.
  

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6. Secure the Oil Pump to the Main Bearing Caps

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Once the internal components are assembled and clearances are confirmed, the pump can be mounted onto the main bearing caps in the engine.

• Position the Oil Pump: Align the oil pump on the main bearing caps, ensuring any shims used to achieve proper clearance are in place.
• Insert Mounting Bolts: Place the mounting bolts through the pump and into the main bearing caps. Tighten the bolts by hand initially to ensure correct alignment.
• Torque the Mounting Bolts: Use a torque wrench to tighten the bolts to the manufacturer’s specifications, typically between 35-39 lb-ft for the Series 71 oil pump. Proper torque secures the pump without risk of loosening under engine vibration.
• Verify Alignment: After securing the bolts, verify that the oil pump remains aligned with the crankshaft and other engine components. Misalignment could lead to gear wear or poor oil flow.
  

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7. Final Check and Reinstallation of the Oil Pan

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Once the oil pump is securely mounted, the final steps involve sealing the pump assembly and reattaching the oil pan.

• Inspect Oil Pump Seals and Gaskets: Before reinstalling the oil pan, inspect all seals and gaskets around the oil pump for any signs of wear or damage. Replace any worn gaskets to ensure a tight seal and prevent oil leaks.
• Install a New Oil Pan Gasket: Position a new oil pan gasket to ensure a proper seal between the oil pan and engine block. This will help prevent oil leaks and maintain oil pressure.
• Attach the Oil Pan: Carefully position the oil pan onto the engine block, aligning it with the gasket. Insert the oil pan bolts and tighten them by hand initially to maintain alignment.
• Torque the Oil Pan Bolts: Use a torque wrench to tighten the oil pan bolts in a cross-pattern to the manufacturer’s specifications. Proper torque on the oil pan bolts is essential to create a tight seal and prevent oil leaks under high-pressure conditions.
  

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8. Post-Reassembly Inspection and Testing

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After reassembly, a final inspection and test can ensure that the oil pump is fully functional and ready for operation.

• Manual Rotation Test: Rotate the crankshaft manually to verify that the oil pump gears turn smoothly. This test confirms that no binding or resistance exists and that the pump is correctly aligned.
• Oil Pressure Check: Once the engine is reassembled and oil is added, start the engine and monitor the oil pressure gauge to confirm proper pressure. If the pressure is below specifications, shut off the engine and inspect the oil pump installation for any issues.
• Leak Check: Observe the oil pan and pump area for any oil leaks while the engine is running. Proper sealing during reassembly should prevent any leaks, but it’s crucial to confirm this.

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By following these detailed reassembly steps, you can ensure that the Detroit Diesel Series 71 oil pump is correctly assembled and ready to deliver reliable oil flow and pressure. Attention to detail during reassembly will help maintain optimal lubrication throughout the engine, enhancing performance and longevity.

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