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The Garrett GTA42 turbocharger is used on all Series 60G automotive engines. See Figure 35342 . ‪

Note: On April 2000, all Series 60 engines with GT40 and GT42 turbochargers were replaced by GTA40 and GTA42 turbos. The GTA turbo has a CHRA (center housing rotating assembly) with a boreless compressor wheel.

1. Compressor Housing ‪

4. Wastegate Actuator ‪

2. Actuator Hose ‪

5. Turbine Housing ‪

3. Water-cooled Center Housing ‪

6. V-Band Joints ‪

GTA42 Turbocharger Assembly (Coach)

The turbocharger is designed to increase the overall power and efficiency of the engine. Power to drive the turbocharger is extracted from the energy in the engine exhaust gas. ‪

The CHRA consists of a turbine wheel and shaft, a compressor wheel, and a center housing that serves to support the rotating assembly, bearings, seals, a turbine housing, and a compressor housing. The center housing has connections for oil inlet, oil outlet, water inlet and water outlet fittings. ‪

The rotating assembly consists of a turbine wheel and shaft assembly, piston ring(s), thrust spacer, compressor wheel, and wheel retaining nut. The rotating assembly is supported on two pressure-lubricated bearings that are retained in the center housing by snap rings. Internal oil passages are drilled in the center housing to provide lubrication to the turbine wheel shaft bearings, thrust washer, thrust collar, and thrust spacer. Internal water passages provide cooling and subsequent protection against oil cooking in the housing. ‪

The turbine housing is a heat-resistant alloy casting that encloses the turbine wheel and provides a flanged engine exhaust gas inlet and an axially located turbocharger exhaust gas outlet. The turbine housing is secured to the turbine end of the center housing. An internal turbine bypass valve, commonly called a wastegate, allows exhaust gas to flow around the turbine wheel. This provides control over the maximum boost pressure. ‪

The wastegate is controlled with a pneumatic actuator mounted on the side of the turbine housing. The Series 60G coach engine turbocharger has an actuator with a single hose port on the top side of the actuator can with a silicon hose that runs to a port on the compressor cover. See Figure 35342 . Air pressure from the compressor outlet is fed through the line to the top side of the actuator, which opens the wastegate valve at a specified pressure. ‪

The turbocharger is mounted on the exhaust outlet flange of the engine exhaust manifold. After the engine is started, the exhaust gases flow from the engine and through the turbine housing causing the turbine wheel and shaft to rotate. See Figure 35354 . ‪

Schematic Air Flow Diagram (Series 60G Automotive)

The gases are discharged into the exhaust system after passing through the turbine housing. On automotive engines, an oxygen sensor and exhaust temperature sensor are installed within 12 inches of the turbocharger turbine outlet. A harness connects the sensors to the ECM. ‪

The compressor wheel, in the compressor housing, is mounted on the opposite end of the turbine wheel shaft and rotates with the turbine wheel. The compressor wheel draws in clean air, compresses it, and delivers high pressure air through the intake manifold to the engine cylinders. ‪

Oil for lubricating the turbocharger is supplied under pressure through an external oil line extending from the oil filter adaptor to the top of the center housing. Water for cooling the bearing housing is supplied from the oil cooler, and is returned to the top of the thermostat housing. See Figure 27368 . ‪

1. Elbow, Oil Drain Tube ‪

9. Connector, Oil Supply Tube (from oil filter adaptor) ‪

2. Tube, Turbo Oil Drain ‪

10. Tube Assembly, Turbo Oil Supply ‪

3. Bolt, and Lockwashers, Oil Drain Tube Mounting ‪

11. Bolt, Oil Supply Tube Clip ‪

4. Gasket, Oil Drain Tube ‪

12. Clip, Oil Supply Tube ‪

5. Elbow ‪

13. Gasket, Turbo Exhaust Inlet ‪

6. Clamp ‪

14. Water Supply Line ‪

7. Nut, and Washer Turbo Mounting ‪

15. Water Return Line ‪

8. Turbocharger Assembly ‪

Turbocharger Oil/Water Lines Series 60 Gas (Automotive)

From the oil inlet in the center housing, the oil flows through the drilled oil passages in the housing to the shaft bearings, thrust ring, thrust bearing, and backplate or thrust plate. See Figure 27366 . ‪

1. Compressor Wheel ‪

6. Shaft ‪

2. Thrust Bearing ‪

7. Turbine Wheel ‪

3. Backplate ‪

8. Shaft Bearings ‪

4. Oil Inlet ‪

9. Oil Outlet ‪

5. Center Housing ‪

10. Water passages ‪

Turbocharger Oil Flow Diagram (Series 60G, Automotive)

The oil returns by gravity to the engine oil pan through an external oil line extending from the bottom of the turbocharger center housing to the cylinder block. Water flows through the bearing housing in a U-shape flow path, removing heat generated by the hot exhaust gas in the turbine. ‪

Repair or Replacement of Turbocharger (Series 60 Gas Automotive Engine)

To determine if repair is possible or replacement of the turbocharger is necessary perform the following procedure. See Figure 21458 . ‪

Flowchart for Repair or Replacement of Turbocharger (Series 60 Gas, Automotive)

Cleaning and Removal of Turbocharger (Series 60G Automotive Engine)

Cleaning the turbocharger is not necessary before removal. ‪


To avoid injury from hot surfaces, wear protective gloves, or allow engine to cool before removing any component.

Prior to removal, visually check for: ‪

  1. Missing or loose nuts and bolts.
  2. Loose or damaged intake and exhaust ducting.
  3. Damaged oil supply and drain lines.
  4. Cracked or deteriorating turbocharger housings.
  5. External oil leakage.
  6. Damaged water supply and return lines.
  7. Replace damaged parts with new parts.

To remove the turbocharger, perform the following: ‪


Do not attempt to remove carbon or dirt buildup on the compressor or turbine wheels without removing the turbocharger from the engine. If chunks of carbon are left on the blades, an unbalanced condition will exist and subsequent failure of the bearings will result if the turbocharger is operated. However, it is not necessary to disassemble the turbocharger to remove dirt or dust buildup. ‪

  1. Disconnect and remove the CAC ducting at the compressor housing.
  2. Disconnect and remove the air inlet hose attached to the compressor housing.
  3. Disconnect the exhaust outlet pipe from the turbine housing of the turbocharger. For proper operation, the turbocharger rotating assembly must turn freely. Whenever the exhaust ducting is removed, spin the turbine wheel by hand.
  4. Remove the inlet oil line from the top of the center housing.
  5. Remove the oil drain line from the bottom of the center housing.

    Note: Be sure to drain coolant before removing water lines from bearing housing.

  6. Remove water lines from bearing housing.
  7. Remove actuator return line on bottom port of actuator.
  8. Attach a chain hoist and a suitable lifting sling to the turbocharger assembly.
  9. Remove the nuts securing the turbocharger assembly to the exhaust manifold. Then, lift the turbocharger assembly away from the engine and place it on a bench.
  10. Cover the end of the oil drain line, the oil outlet line, water supply, water return, the air inlet and the exhaust outlet openings on the engine and turbocharger to prevent the entry of foreign material.


    To avoid injury from improper use of chemicals, follow the chemical manufacturer's usage, handling, and disposal instructions. Observe all manufacturer's cautions.

Disassembly of Turbochargers (Series 60G Automotive Engine)

Disassemble the turbocharger as follows: ‪

Note: Clean the exterior of the turbocharger with a non-caustic cleaning solvent before disassembly.

  1. Mark the related positions of the compressor housing, center housing and turbine housing with a punch or scribe to assure reassembly in the same relative position.


    Exercise care when removing the compressor housing and turbine housing to prevent damage to the compressor and turbine wheels. ‪

  2. Loosen the V-band coupling securing the compressor housing to the backplate assembly and remove the compressor housing and V-band.
  3. Perform the following steps to disassemble the GTA42 turbocharger: See Figure 20595 .
    1. Loosen the V-band coupling securing the turbine housing to the center housing.
    2. Remove the turbine housing from the center housing.
    3. 1. Compressor Housing ‪

      3. Turbine Housing ‪

      2. Compressor Housing and Rotating Assembly ‪

      4. V-Band Couplings ‪

      GTA42 Turbocharger

Inspection and Cleaning of Turbocharger (Series 60G Automotive Engine)

Damage can result from a contaminated exhaust system. Any debris left in the exhaust system after service work can fall back into the exhaust wheel. If large enough, these particles may cause turbine wheel damage at initial engine startup. The exhaust manifold and exhaust piping attached to the turbocharger should also be inspected for debris and cleaned, if necessary, before being installed. ‪

Any time the charge air cooler is removed, all charge air cooling system components must be inspected to make sure they are clean and free of any casting slag, core sand, welding slag, or any other contaminants that could break free during engine operation and damage the turbine wheel. ‪

Inspect the disassembled turbocharger, discarding any damaged parts, in the following manner: ‪

  1. Visually check for nicked, crossed or stripped threads.
  2. Visually check the turbine wheel shroud and turbine wheel for signs of rubbing.
  3. Visually check the compressor wheel for signs of rubbing or damage from foreign material. The wheel must be free of dirt and other foreign material.
  4. Check actuator can for external damage.
  5. Check actuator pressure setting; refer to section .
  6. Check compressor cover recirculation valve (coach only).
  7. Visually check wastegate lever arm, valves, and ports. Ensure the ports are completely covered by the valves.
  8. Check the bearing axial end play:
    1. Clamp the center housing assembly in a bench vise equipped with soft jaws. See Figure 20423 .
    2. Fasten the dial indicator and magnetic clamp, J 7872-2 , to the center housing so that the indicator tip rests on the end of the rotating shaft on the compressor side. See Figure 20423 .
    3. Checking Bearing Axial End Play

    4. Move the shaft axially back and forth by hand. The total indicator reading (thrust float) should be 0.0127-0.0889 mm 0.0005-0.0035 in.). If the total dial indicator readings do not fall within the specified limits, replace the rotating assembly.
  9. Check the shaft radial movement as follows:

    Due to the internal construction of the GTA42 bearing housing, access to the shaft through the oil drain is not possible. Therefore, radial movement cannot be accurately measured to determine the condition of radial turbine bearings. ‪

    To determine the general condition of the radial bearings, check radial end play after the turbocharger is cleaned and assembled. Push on the end of the shaft, towards the side of the compressor (or turbine) housing. If the wheel contacts either housing, the radial bearings may be worn out, and the CHRA should be replaced (be sure to check if the housing is seated and installed correctly also). ‪

  10. Service of the center housing rotating assembly (CHRA)

    The CHRA is serviced by replacement only. Do not attempt disassembly of the CHRA, as possible shaft imbalance and damage may result. ‪

Checking Wastegate Calibration for the Series 60G Automotive Engine

This procedure provides a method for verifying proper wastegate calibration. ‪

  1. Remove hose from wastegate actuator (for gensets, remove line on top side of can).
  2. Set-up an indicator at the end of the wastegate actuator adjusting rod to measure actuator rod travel. The indicator should have a minimum travel of 0.100 in.
  3. Connect regulator and pressure gage set-up to wastegate actuator. See Figure 27284 .

    1. Hose to Wastegate Actuator ‪

    4. Supply Air Shutoff Valve ‪

    2. Vent Valve ‪

    5. Pressure Regulator ‪

    3. Pressure Gage ‪

    6. Shop Air Supply ‪

    Checking Wastegate Calibration for the Series 60G Automotive Engine

  4. Apply specified calibration pressure (listed in Table ) to the wastegate actuator.



    Set Pressure Travel at 0.04 in. Rod

    Coach ‪

    330 Hp ‪

    24 lb/in.2

    Series 60G Wastegate Calibration Pressure at 0.04 in. Rod Travel


    For genset turbochargers, NEVER apply pressure to bottom part of actuator can. Damage to actuator may result. ‪

  5. Close air supply shutoff valve. The pressure should hold at the specified pressure. If not, check air hose and fitting connections for leaks. If none are found, replace wastegate actuator assembly. Refer to section .
  6. Open vent to relieve pressure. Check gage for zero pressure reading. Adjust regulator to zero pressure and close vent valve.
  7. Adjust dial indicator so it just contacts the actuator rod end and adjust to zero reading.
  8. Open air supply shutoff valve and slowly adjust regulator until dial indicator reads 0.040 in. Switch pressure on and off, opening and closing supply air and vent valves, to make certain dial indicator travel is from 0.00 in. to 0.040 in. and that the pressure reading is consistent.
  9. For currently calibrated wastegate actuator, a pressure within 0.25 lb/in.2 of the value listed in Table , will be required to obtain precisely 0.040 in. actuator travel. If the pressure required is outside this range, wastegate adjustment is necessary; refer to section .

Removal and Replacement of Series 60G Wastegate Actuator

This procedure describes the removal of a actuator currently mounted on a turbocharger, and the replacement with a new service actuator. Further adjustment of the actuator will be necessary to achieve the correct pressure setting, listed in Table . ‪

  1. Remove actuator hose from the top side of the actuator can. With the pressure gage set-up (see Figure 27284 ), apply enough pressure to the actuator can until the rod begins to move; refer to section .
  2. Remove the retaining clip that holds the actuator rod end on the wastegate lever pin. Lift rod off the wastegate lever pin.


    Never remove the rod end from the wastegate lever pin unless pressure is applied to the top side actuator port; otherwise, damage to the actuator diaphragm may result. ‪

  3. Remove the lock nuts that secure the actuator can to the base of the actuator bracket, and remove the can from the turbocharger assembly.

Replace wastegate actuator as follows: ‪

  1. Install actuator can on bracket; tighten lock nuts.
  2. Using pressure gage set-up, apply enough pressure to the new service actuator can until the rod begins to move.
  3. Adjust actuator rod end by turning either clockwise or counterclockwise on rod so that the rod end hole lines up with the wastegate lever arm, while wastegate is held shut pin, slip rod over pin.
  4. Before installing the retaining clip again, the rod end will need to be adjusted to the correct setting. Refer to section .

Setting the Wastegate on the Series 60G Automotive Engine

This procedure describes the set pressure adjustment of an installed wastegate actuator. Before following this procedure, first check the actuator set pressure to see if adjustment is needed refer to section . ‪

  1. Loosen the jam nut that secures the rod end on the actuator rod. If locking collar is present on the actuator rod, remove and discard collar, see Figure 27283 .

    1. Wastegate Actuator Assembly ‪

    4. Adjusting Rod End ‪

    2. Locking Collar ‪

    5. Retainer Clip ‪

    3. Jam Nut ‪

    6. Wastegate Lever and Pin Assembly ‪

    Wastegate Adjustment

  2. Remove the retaining clip that holds the actuator rod end on the wastegate lever arm pin.


    For genset actuator, never apply pressure to the bottom side of actuator port. Damage to the actuator may result. ‪

  3. Using pressure gage setup (see Figure 27283 ) apply enough pressure to the top side actuator can port until the rod begins to move, lifting the wastegate valve off of it's seal.
  4. Slip rod end off the wastegate lever arm pin.
  5. Adjust rod as needed
    • To INCREASE pressure setting at 0.04 in. turn rod end CLOCKWISE.
    • To DECREASE pressure setting at 0.04 in. turn rod end COUNTERCLOCKWISE.
  6. With pressure still applied to actuator, replace rod end on wastegate lever arm
  7. Check actuator set pressure again; refer to section .
  8. If actuator is still out of adjustment, repeat this procedure again.
  9. If actuator is within specified set pressure, re-install retaining clip on wastegate lever arm pin.
  10. Tighten jam nut to secure rod end.

Assembly of Turbocharger Series 60G Automotive Engine

Use the following procedure to assemble the turbocharger: ‪


As the parts are assembled, cover the openings to prevent entry of dirt or other foreign material, which may cause component damage. ‪

  1. Cover all openings.
  2. Position the turbine housing as marked at disassembly against the center housing and secure it in place.


    Failure to properly orient the Tee-bolt end of the clamp can result in an exhaust leak, turbine wheel damage or both. ‪

  3. To assemble the GTA42 turbochargers, position the V-band coupling between the turbine housing and center housing so that the Tee-bolt end does not interfere with the turbine housing. Then tighten the V-band coupling nut, as follows:
    1. Lubricate the toggle bolt threads with a high temperature anti-seize compound.
    2. Torque the nut on the V-band toggle bolt to approximately 18 Nm (160 lb in.).
    3. Note: Do not pull a misaligned turbine housing into alignment with the V-band coupling. The parts must be aligned and seated first.

    4. Loosen the V-band coupling nut to approximately 6 Nm (50 lb in.) torque, then torque the nut to 12-15 Nm (106-130 lb in.).
  4. Position the compressor housing as marked at disassembly against the backplate assembly and secure it in place with the V-band coupling.
  5. Lightly lubricate the threads of the toggle bolt with engine oil and torque the nut to 12-15 Nm (106-130 lb in.). This completes the assembly of GTA42 turbocharger.


    The 5/8 in. hex-head turbine housing bolts replaced 3/8 in. hex-head bolts. The 5/8 in. hex-head bolts are required to ensure sufficient clamp load. ‪

  6. Secure the TMF turbine housing with four 5/8 in. hex head bolts.
  7. Torque the bolts to 34 Nm (300 lb in.).

Installation of Turbocharger Series 60G Automotive Engine

To install the turbocharger: ‪

  1. Attach a chain hoist and a suitable lifting sling to the turbocharger assembly.
  2. Remove any covers that were placed over the openings of the air inlet and exhaust outlet openings on the engine and turbocharger when the turbocharger was removed.
  3. Remove any covers on the oil inlet and drain lines, and the oil inlet and drain openings on the turbocharger.
  4. Place the turbocharger assembly into position on the exhaust manifold. Use a new gasket between the exhaust manifold and the turbine housing flange.
  5. Secure the turbocharger to the exhaust flange. Tighten the nuts just enough to hold the turbocharger in place.
  6. Slide the charge air cooler air inlet tube hose over the compressor housing outlet opening and secure it in place with the hose clamps.


    To avoid injury from the sudden release of a high-pressure hose connection, wear a face shield or goggles.


    Do not use any type of lubricant on the inside of any air inlet hose or on the hose contact surfaces of the turbocharger compressor housing, CAC ducting or the intake manifold. ‪

  7. Torque the turbocharger to exhaust manifold locknuts to 58-73 Nm (43-54 lbft).
  8. Install the oil drain line, using a new gasket, between the opening in the bottom side of the turbocharger center housing and the drain hose that runs to the cylinder block. Torque the bolts to 30-38 Nm (22-28 lbft).
  9. Refer to section for verification of proper turbocharger installation.
  10. Install water supply and return lines.