Engine diagram the mounting bolt broke while replacing the thermostat housing what part needs replacing

The exact location of the thermostat varies depending on the particular engine model on your Pontiac Montana. Although 2.0L turbo and non-turbo engines locate the thermostat on the upper section of the engine, other models may follow the lower radiator hose to a lower position on the engine, requiring the removal of one or more components for replacement. see below

• Park your car in a safe place and open the hood.
  
• 2Locate the thermostat housing by following the upper or lower radiator hose from the radiator towards the engine. The end of the hose should be connected to an aluminum or metal housing attached to the engine by two mounting bolts.
  
• 3Remove the air cleaner duct assembly and the crossover exhaust pipe, if necessary, using a wrench and ratchet and socket.
  
• 4Place a drain pan underneath the radiator drain valve. Open the valve and drain some of the coolant to empty the radiator hose; then close the valve.
  
• 5Remove the radiator hose from the thermostat housing by disconnecting the clamp using a pair of rib joint pliers, Phillips screwdriver or ratchet and socket, depending on type of clamp used on your particular model; then remove the hose.
  
• 6Remove the two thermostat housing bolts and lift the housing off the engine. Before removing the thermostat off the engine, pay careful attention to the position of the relief valve on the thermostat in relation to the mounting base on the engine, looking for any special marks. The new thermostat has to be mounted in this same exact position. Also, note that the thermostat spring has to point towards the engine once it is seated on the engine; then remove the thermostat and any gasket material if necessary.
  

Installation

• 1Clean the thermostat housing and engine mounting surfaces from gasket material, if necessary, using a plastic scraper; also, clean the bolt threads of the thermostat housing bolts of sealer, if necessary, using a wire brush.
  
• 2Apply a light coat of Room Temperature Vulcanizing (RTV) sealer to the new paper gasket if your particular model requires one; or install a new O-ring to the center of the thermostat; also, apply a light coat of RTV sealer to the threads of the thermostat housing mounting bolts.
  
• 3Install the new thermostat on the engine mounting base in the same exact position as the old one; install the paper gasket if required and set the thermostat housing in place. Start the housing mounting bolts by hand and then tighten the bolts.
  
• 4Connect the radiator hose to the thermostat housing; then install the crossover exhaust pipe and air cleaner and duct assembly, if necessary. Fill the radiator with new coolant, start the engine and let it reach operating temperature. Check for leaks and add more coolant to the reservoir to bring the level between the Add and Full Hot marks and turn off the engine.
  
• 5Bleed the cooling system if the thermostat housing is provided with a valve screw on it. Once the engine reaches operating temperature, loosen the valve screw until coolant begins to leak through the screw; then tighten the screw again
  

Read more: How to Change a Pontiac Montana Thermostat ' eHow.com http://www.ehow.com/how_4900141_change-pontiac-montana-thermostat.html#ixzz1eRUgRlYC

Follow the upper radiator hose off the radiator to the engine, where the house mounts on the engine is where the thermostat is located, two bolts should hold it on, front top side of the engine on the intake manifold.

Thermostat Removal & Installation 2.2L Engine 2004-2005 To Remove:

1. Drain the cooling system.
   
2. Remove the thermostat housing-to-water pump feed pipe bolts.
   
3. Remove the water pump feed pipe from the thermostat housing .
4. Remove the thermostat from the housing.

To Install:

1. Install the thermostat on the housing.
2. Install the water pump feed pipe on the thermostat housing with the mounting bolts. Tighten 89 in-lb (10 Nm).
3. Fill the cooling system.

2006-2007 To Remove:

1. Drain the cooling system.
2. Disconnect the radiator outlet hose from the surge tank and thermostat housing cover. Thermostat & cover
   
3. Remove the mounting bolts and remove the thermostat housing cover.
4. Remove the thermostat from the housing. Discard the O-ring.

To Install:

1. Using a new O-ring, install the thermostat on the housing.
2. Install the thermostat housing cover with the mounting bolts. Tighten 89 in-lb (10 Nm).
3. Connect the radiator outlet hose to the surge tank and thermostat housing cover.
4. Fill the cooling system.

3.5L Engine (LZ4) W/ Variable Valve Timing & 3.9L Engine To Remove:

1. Drain the cooling system.
2. Remove the air cleaner outlet duct.
3. Disconnect the radiator outlet hose from the thermostat housing. Thermostat 3.9L
   
4. Remove the mounting bolt/stud and remove the thermostat housing.
5. Remove the thermostat from the engine.
6. Clean the sealing surfaces.

To Install:

1. Using a new gasket, install the thermostat on the engine.
2. Install the thermostat housing with the mounting bolts. Tighten 89 in-lb (10 Nm).
3. Connect the radiator outlet hose to the thermostat housing.
4. Install the air cleaner outlet duct.
5. Fill the cooling system.
6. Check the cooling system for leaks.

3.5L Engine (LX9) W/O Variable Valve Timing To Remove:

1. Drain the coolant.
2. Disconnect the radiator hose from the thermostat housing. Thermostat 3.5L
   
3. Remove the mounting bolt/stud and remove the thermostat housing.
4. Remove the housing gasket.
5. Remove the thermostat.
6. Clean the mating surfaces.

To Install:

1. Install the thermostat on the engine.
2. Install the thermostat housing and gasket with the mounting bolts. Tighten 18 ft-lb (25 Nm).
3. Connect the radiator hose to the thermostat housing.
4. Fill the cooling system.
5. Check the cooling system for leaks.

I seriously doubt if you will find the diagram that you are asking for. The thermostat is very easy on most vehicles. Simply follow the upper radiator hose to where it connects to the engine. This would be the thermostat housing. The thermostat hosing is held on by 2 bolts. Remove the 2 bolts and remove the thermostat housing. The thermostat will be under the housing. Pull the old thermostst out and clean the gasket surfaces on both the engine and the thermostat housing. install the new thermostat and thermostat housing gasket and reinstall ithe thermostat and bolts. On some of the Dodge vehicles it is necessary to remove the alternator and/or power steering pump/ A/C compressor brackets to access the thermostat housing bolts.

Thermostat Removal & Installation 3.4L & 3.5L Engine To Remove:

1. Drain the coolant below the level of the thermostat.
2. Remove the air cleaner and duct assembly.
3. Remove the exhaust crossover pipe.
4. Disconnect the radiator hose from the thermostat housing.
   
   
5. Remove the mounting bolts and remove the thermostat housing.
6. Remove the housing gasket.
7. Remove the thermostat.
8. Clean the mating surfaces.

To Install:

1. Install the thermostat on the engine. NOTE: Apply RTV sealer to the thermostat housing bolt threads.
   
2. Install the thermostat housing and gasket with the mounting bolts. Tighten 18 ft-lb (25 Nm).
3. Connect the radiator hose to the thermostat housing.
4. Install the exhaust crossover pipe.
5. Install the air cleaner and duct assembly.
6. Fill the cooling system.
7. Check the cooling system for leaks.

3.6L Engine To Remove:

1. Remove the air cleaner.
2. Remove the throttle body.
3. Remove the heater pipes.
4. Remove the coolant inlet pipe. Thermostat 3.6L
   
   
5. Remove the thermostat mounting bolts and remove the thermostat.
6. Clean the thermostat and heater pipe mating surfaces.

To Install:

1. Place the thermostat in the housing with a new gasket.
2. Install the thermostat and gasket on the engine with the mounting bolts. Tighten 89 in-lb (10 Nm).
3. Install the coolant inlet pipe.
4. Install the heater pipes.
5. Install the throttle body.
6. Install the air cleaner.
7. Fill the cooling system and perform a leak test.

Partially drain coolant level to below thermostat level if nessasary. Follow top radiator hose over to engine. Where the top radiator hose stops at engine is where the thermostat is. Hose is connected to a pipe ( called a thermostat housing) that bolts to the engine. Remove components if they are in the way of accessing the two bolts or nuts that hold down the thermostat housing. Remove thermostat housing. Thermostat is under the housing. Replace thermostat and paper gasket or rubber o-ring. Be sure to clean surfaces of area where the gasket is mounted. Reinstall thermostat housing but do not over tighten the housing bolts or nuts. Reinstrall components removed and refill coolant to proper level. Do not forget to close radiator drain. Do not put radiator cap on at this time. Start engine and let run for a few minutes to get air out of system. Stop engine and refill coolant if needed. Install radiator cap and check coolant resevoir and fill to proper level if needed. Hope this helps.

Check this location diagrams...



Fig. Exploded view of the thermostat (3) showing the thermostat housing (1,2) location on the engine block (4)-3.7L & 4.7L engines




Fig. Exploded view of the thermostat housing (2) and mounting bolts (1), lower radiator hose (4) and hose clamp (3)-5.7L engine

I hope this helps (remember to comment and rate this answer).

Thermostat Removal & Installation 2.2L Engine To Remove:

1. Remove the exhaust manifold. If equipped with an automatic transmission.
2. Drain the cooling system.
3. Remove or disconnect the following:
   
   
   • Thermostat housing to water pump feed pipe bolts.
     
     
   • Thermostat housing to water pump feed pipe.
   • Thermostat.

To Install:

1. Install or connect the following:
   • Thermostat.
   • Thermostat housing to water pump feed pipe.
   • Thermostat housing to water pump feed pipe bolt.
     1. Tighten bolt to 89 in lbs (10 Nm).
   • Exhaust manifold if equipped with an automatic transmission.
2. Fill the cooling system.

2.4L Engine To Remove:
Thermostat assembly 2.4L

1. Drain the cooling system.
2. Remove the exhaust manifold heat shield.
3. Remove the coolant inlet housing mounting bolts through the exhaust manifold.
4. Raise and safely support the vehicle.
5. Remove the coolant inlet housing stud from the oil pan.
6. Remove wheel and tire assembly.
7. Remove the engine splash shield.
8. Remove the mounting bolts from the transaxle-to-engine block support. Remove the support.
9. Remove the coolant housing pipe.
10. Remove the thermostat.
11. Clean the mating surfaces.

To Install:

1. Install the thermostat.
2. Install the coolant housing pipe.
3. Install and secure the transaxle support-to-engine block mounting bolts.
4. Install the engine splash shield.
5. Install the wheel and tire assembly.
6. Install the coolant inlet housing stud to the oil pan.
   • Tighten to 19 ft lb (26 Nm).
7. Lower the vehicle.
8. Install the coolant inlet housing bolts through the exhaust manifold.
   • Tighten the coolant inlet housing bolts to 10 ft lb (14 Nm).
9. Install the exhaust manifold heat shield.
10. Fill the cooling system.
11. Inspect the system for leaks.

3.4L Engine To Remove:

1. Drain the cooling system.
2. Remove the air cleaner.
3. Remove exhaust crossover pipe.
4. Disconnect the surge tank line fitting from the coolant outlet.
5. Remove the thermostat housing to intake manifold bolts.
6. Remove the thermostat housing outlet and thermostat.

To Install:

1. Install the thermostat and housing outlet.
2. Install the thermostat housing bolts.
   • Tighten the thermostat housing bolts to 18 ft lb (25 Nm).
3. Install exhaust crossover pipe.
4. Connect the surge tank line fitting to the coolant outlet.
   • Tighten the fittings to 15 ft lb (21 Nm).
5. Install the air cleaner.
6. Fill the cooling system.
7. Inspect the system for leaks

Thermostat Removal & Installation 3.4L & 3.5L Engine To Remove:

1. Drain the coolant below the level of the thermostat.
2. Remove the air cleaner and duct assembly.
3. Remove the exhaust crossover pipe.
4. Disconnect the radiator hose from the thermostat housing.
   
   
5. Remove the mounting bolts and remove the thermostat housing.
6. Remove the housing gasket.
7. Remove the thermostat.
8. Clean the mating surfaces.

To Install:

1. Install the thermostat on the engine. NOTE: Apply RTV sealer to the thermostat housing bolt threads.
   
2. Install the thermostat housing and gasket with the mounting bolts. Tighten 18 ft-lb (25 Nm).
3. Connect the radiator hose to the thermostat housing.
4. Install the exhaust crossover pipe.
5. Install the air cleaner and duct assembly.
6. Fill the cooling system.
7. Check the cooling system for leaks.

3.6L Engine To Remove:

1. Remove the air cleaner.
2. Remove the throttle body.
3. Remove the heater pipes.
4. Remove the coolant inlet pipe. Thermostat 3.6L
   
   
5. Remove the thermostat mounting bolts and remove the thermostat.
6. Clean the thermostat and heater pipe mating surfaces.

To Install:

1. Place the thermostat in the housing with a new gasket.
2. Install the thermostat and gasket on the engine with the mounting bolts. Tighten 89 in-lb (10 Nm).
3. Install the coolant inlet pipe.
4. Install the heater pipes.
5. Install the throttle body.
6. Install the air cleaner.
7. Fill the cooling system and perform a leak test.

Removal & Installation 3.9L, 5.2L & 5.9L Engines To Remove:

1. Before servicing the vehicle, refer to the precautions at the beginning of this section.
2. Remove or disconnect the following:
   • Negative battery cable
   • Coolant until level is below thermostat
     
     
   • Support bracket located near rear of alternator (A/C Vehicles)
     
     
   • Alternator drive belt by attaching a wrench to the pulley mounting bolt of the automatic tensioner, rotating the tensioner clockwise to release belt tension, and removing the belt:
   • Alternator mounting bolts, but do not remove any wiring at alternator
   • 4WD indicator lamp wiring harness (4WD vehicles)
   • Alternator and position aside WARNING
     When servicing constant tension hose clamps, use only tools designed for servicing this type of clamp, such as special clamp tool (number 6094). Always wear safety glasses when servicing constant tension clamps. Always replace constant tension clamps with the same numbered clamp.
     
   • Radiator hose clamp and upper radiator hose at thermostat housing and position wiring harness aside to gain access to thermostat
     
     
   • Thermostat housing mounting bolts, thermostat housing, gasket and thermostat

To Install:

1. Clean intake manifold and thermostat housing mating surfaces.
2. Install or connect the following:
   • Thermostat (spring side down) into recessed machined groove on intake manifold
   • Gasket on intake manifold and over thermostat
     
     
   • Thermostat housing to intake manifold NOTE: The word FRONT is stamped on housing and must be placed towards front of vehicle.
     
   • Housing-to-intake manifold bolts.
     1. Torque to: 200 inch lbs. (23 Nm)
   • Upper radiator hose to thermostat housing
     
     
   • Alternator (A/C Vehicles)
     1. Torque to: 30 ft. lbs. (41 Nm)
   • Support bracket
     1. Torque to: 40 ft. lbs. (54 Nm)
   • Drive belt over all pulleys except idler pulley
   • Socket/wrench to pulley mounting bolt of automatic tensioner and rotate clockwise
   • Belt over idler pulley, let tensioner rotate back into place and remove wrench
   • Coolant
   • Negative battery cable
3. Start and warm the engine and check for leaks.

4.7L Engine To Remove:

1. Before servicing the vehicle, refer to the precautions at the beginning of this section.
2. Remove or disconnect the following:
   • Negative battery cable
   • Coolant
3. Safely raise and support the vehicle.
4. Remove or disconnect the following:
   • Splash shield
   • Lower radiator hose clamp and lower radiator hose at thermostat housing 4.7L engine shown 3.7L similar
     
     
   • Thermostat housing mounting bolts, thermostat housing and thermostat

To Install:

1. Clean timing chain cover and thermostat housing mating surfaces.
2. Install or connect the following:
   • Thermostat (spring side down) into recessed machined groove on timing chain cover
   • Thermostat housing on timing chain cover
   • Housing-to-timing chain cover bolts.
     1. Torque to: 112 inch lbs. (13 Nm)
   • Lower radiator hose on thermostat housing
   • Splash shield
3. Lower vehicle.
4. Fill cooling system.
5. Connect negative battery cable to battery.
6. Start the engine and check for leaks.