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How do I change the thermostat on a 2003 VW Passat Wagon with a V6 engine


The thermostat is located in



The thermostat is located in the engine block just to the side of the water pump underneath the housing where the upper radiator hose is attached.

  1. Remove the lower engine shield.
  2.  
  3. Place a large drain pan under the vehicle to collect the coolant.
  4.  
  5. Remove the radiator cap and drain the cooling system into a suitable container.

  6.  
  7. Place a large drain pan under the engine block drain located at the bottom of the engine near the vicinity of the flywheel and the oil pan.
  8.  
  9. Drain the engine block coolant into a suitable container.
  10.  
  11. Place the (hood) lock carrier in the 'service position'. For additional information, please refer to the following topic(s): Body And Trim, Service Position, Front Bumper, Hood Lock Carrier.

  12.  
  13. Remove the accessory drive belt. For additional information, please refer to the following topic(s): General Information And Maintenance, Routing Maintenance And Tune-Up.
  14.  
  15. If installed, remove the upper front engine cover.
  16.  
  17. Remove the toothed camshaft drive belt from the right side cylinder head to allow enough access to remove the thermostat housing. Cover and protect the drive belt from residual coolant.
  18.  
  19. Remove the mounting fasteners; remove the housing, then the thermostat.
  20.  





Click image to see an enlarged view

Fig. An exploded view of the water pump, thermostat housing and thermostat-2.8L V6 engines




Click image to see an enlarged view

Fig. Lubricate the O-ring with coolant and make sure the thermostat is installed with the bleeder facing up-2.8L V6 engines

To install:



WARNING

The thermostat vent valve must be installed facing up otherwise the cooling system may develop air pockets and allow the engine to overheat.



  1. Using new O-ring, install the thermostat making sure the vent valve is installed facing up.
  2.  
  3. Install the thermostat housing and torque the housing the bolts to 88 inch lbs. (10 Nm).
  4.  
  5. Inspect the camshaft drive belt for wear and damage and replace if necessary. If contaminated with fluids or lubricants, it should be replaced. For additional information, please refer to the following topic(s): General Information And Maintenance, Routine Maintenance And Tune-Up, Engine And Engine Overhaul, Timing Belt And Sprockets.

  6.  
  7. Installation is in reverse order of removal noting the following:
  8.  
  9. Top off cooling system with the recommended fluid and concentration. For additional information, please refer to the following topic(s): General Information And Maintenance, Fluids And Lubricants.
  10.  


2.8L VR6 Engine






Click image to see an enlarged view

Fig. Exploded view of a VR6 thermostat housing

The thermostat is mounted in the housing and located on the rear of the cylinder head.

  1. Drain the engine coolant into a suitable container.
  2.  
  3. Remove the mounting bolts from the flange.
  4.  
  5. Remove the flange and the thermostat.
  6.  


To install:

  1. Install the thermostat with a new O-ring.
  2.  
  3. Install the thermostat housing.
  4.  
  5. Install and tighten the fasteners.
  6.  
  7. Top off cooling system with the recommended fluid and concentration. For additional information, please refer to the following topic(s): General Information And Maintenance, Fluids And Lubricants.

  8.  


4-Cylinder






Click image to see an enlarged view

Fig. Remove the housing bolts




Click image to see an enlarged view

Fig. Once all bolts have been remove, pull the thermostat housing away from the bottom of the water pump unit




Click image to see an enlarged view

Fig. Note the position of the thermostat and gasket



NOTE
On some models the thermostat is in the bottom of the water pump housing.



  1. Place a large drain pan under the vehicle to collect the coolant.
  2.  
  3. Remove the radiator cap and drain the cooling system.

  4.  
  5. Loosen one bolt at a time until coolant begins to flow.
  6.  
  7. Remove both bolts and remove the thermostat.
  8.  


To install:

  1. Install the new O-ring.
  2.  
  3. Torque the housing the bolts to 7 ft. lbs. (10 Nm).
  4.  


The thermostat is located in the bottom of the water pump housing.

  1. If equipped, remove the lower engine shield.
  2.  
  3. Place a large drain pan under the vehicle to collect the coolant.
  4.  
  5. Remove the radiator cap and drain the cooling system into a suitable container.
  6.  
  7. On 1.8L engines, remove the water pump housing drain plug.

  8.  
  9. Loosen one bolt at a time until coolant begins to flow.
  10.  
  11. Remove both bolts and remove the thermostat.
  12.  





Click image to see an enlarged view

Fig. Remove the housing bolts




Click image to see an enlarged view

Fig. Once the bolts have been removed, pull the thermostat housing away from the bottom of the water pump unit




Click image to see an enlarged view

Fig. Note the position of the thermostat and gasket




Click image to see an enlarged view

Fig. The 1.8L engines have a water pump drain plug near the thermostat housing




Click image to see an enlarged view

Fig. An exploded view of the water pump, pump housing and thermostat-1.8L engine illustrated




Click image to see an enlarged view

Fig. The 1.8L water pump, drain and thermostat housing

To install:

  1. Install the thermostat using new O-ring.
  2.  
  3. If removed, install the water pump drain plug with a new O-ring and tighten to 22 ft. lbs. (30 Nm).

  4.  
  5. Torque the housing the bolts to 88 inch lbs. (10 Nm).
  6.  
  7. Top off cooling system with the recommended fluid and concentration. For additional information, please refer to the following topic(s): General Information And Maintenance, Fluids And Lubricants.
  8.  


VR-6






Click image to see an enlarged view

Fig. Exploded view of a VR6 thermostat housing

On 6 cylinder models, the thermostat is mounted in the housing. The thermostat housing is located on the rear of the cylinder head.

  1. Drain the engine coolant.

  2.  
  3. Remove the mounting bolts from the flange.
  4.  
  5. Remove the flange and the thermostat.
  6.  


To install:

  1. Install the new thermostat and O-ring.
  2.  
  3. Install the thermostat housing.
  4.  
  5. Install and tighten the fasteners.
  6.  
  7. Fill the cooling system with approved antifreeze.
  8.  


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