Bolts to manifold & exhaust rusted

I suggest you use all new exhaust manifold hardware and torque new bolts to 20 Ft Lbs.
4.5L and 4.9L Engines
RIGHT
Disconnect the negative battery cable. Remove the air cleaner. Remove the exhaust crossover pipe. Disconnect the oxygen and coolant temperature sensors. Remove the catalytic converter-to-AIR pipe clip bolt. Remove the upper manifold-to-cylinder head bolts. Raise and safely support the vehicle. Disconnect the converter air pipe bracket from the stud and remove the converter-to-manifold exhaust pipe. Support the engine cradle with screw jacks and remove the rear cradle bolts. Loosen the front cradle bolts and slightly lower the Engine cradle. Remove the remaining exhaust manifold-to-cylinder head bolts, the AIR pipe, and the manifold. Clean the gasket mounting surfaces.
To install:
Install the exhaust manifold and replace the AIR pipe. Tighten the manifold mounting bolts to 16-18 ft. lbs. (21-24 Nm). Install the manifold-to-converter exhaust pipe and replace the converter air pipe bracket to the stud. Raise the Engine cradle and install the rear cradle bolts. Tighten to 75 ft. lbs. (102 Nm). Lower the vehicle. Replace the upper manifold-to-cylinder head bolts. Replace the converter air pipe to AIR pipe clip bolt. Connect the coolant temperature and oxygen sensor connectors. Replace the exhaust crossover pipe. Replace the air cleaner and connect the negative battery cable. Start the Engine and check for leaks.

the manifold will have to be pulled off
rusted bolts and nuts can be removed with the application of heat on the nut bolt followed quick cooling with wd -40
it breaks the rust seal
use rust penetrant liberly

5.2 liter V8 engine?

Remove the four front skid-plate bolts holding the front skid plate, using a ratchet and socket. Remove the skid plate.

Pull the plastic splash shield away from the vehicle, loosening the retaining clips. Remove the splash shield.

Place an oil drain container under the oil pan. Loosen the drain fitting with a wrench until oil drains from the pan. When oil is done draining, tighten the drain fitting.

Disconnect the electrical connections running to the starter motor. Remove the starter motor mounting bolts with a ratchet and socket, then remove the starter motor.

Remove the oxygen sensor socket from the exhaust pipe, using a wrench.

Remove the exhaust manifold bolts where the exhaust meets the manifold on both sides, using a ratchet and socket

Place an jack under the transmission to support it. Remove the pressure on the transmission crossmember.

Remove the bolts that hold the transmission crossmember in place, using a ratchet and socket. Then remove the crossmember. Place a jack stand under the transmission to keep the transmission from falling off the jack if hit. Once removed, the exhaust will hang down, allowing enough room to remove the oil pan.

Disconnect the oil level sensor and the nut retaining the transmission cooling lines, using a wrench.

Remove the oil pan bolts with a ratchet and socket, then remove the oil pan and gasket.

Clean the mounting surfaces of the new oil pan and engine block. Make sure what ever you use to clean the surfaces dosn't gouge the metal.

Place a coat of RTV (gasket) sealer on the engine block where the pan will meet the rear main cap.

Place the new gasket on the pan and push the new oil pan into place. Finger tighten the oil pan mounting bolts to hold it in place. Tighten the bolts with a torque wrench to 18 ft-lbs. DO NOT OVER TIGHTEN THE BOLTS! Doing so will cause the gasket to deform and create leaks!

Connect the oil level sensor and the nut retaining the transmission cooling lines, using a wrench.

Place the exhaust back into position and replace the transmission crossmember bolts and crossmember with a ratchet and socket.

Remove the jack supporting the transmission.

Connect the exhaust back to both sides of the manifold, tightening the bolts with a torque wrench to 20 ft-lbs.

Attach the oxygen sensor socket to the exhaust pipe with a wrench.

Replace the starter motor by installing the starter motor mounting bolts with a ratchet and socket. Connect the electrical connections to the starter motor that were disconnected during removal.

Push the retaining clips on the plastic splash shield into the appropriate retaining clip holes.

Replace the front skid plate by replacing the four front skid plate bolts with a ratchet and socket.

Fill the engine with 5 quarts of oil. Make sure to check the level on the dipstick to find the exact level when filling.

Front Pipe REMOVAL & INSTALLATION Pipe Without Catalytic Converter

1. Before removing any component of the exhaust system, always squirt a liquid rust dissolving agent onto the fasteners for ease of removal..
2. Raise and support the front of the vehicle on jackstands.
3. Remove the exhaust pipe-to-manifold nuts.
4. Support the catalytic converter, then disconnect the pipe from the converter. Remove the pipe.
5. Remove the exhaust gaskets. To install:
   
6. Be sure to use all new gaskets when required. Assemble the system, check the clearance and tighten the bolts to about 15-30 ft. lbs. (20-41 Nm). Fig. 1: Front exhaust pipe connection common on vehicles with the catalytic converter not included
   
   
7. All clamps should be tightened to about 18-25 ft. lbs. (24-34 Nm). Do overtighten the clamps. If pipes become dented they can leak.

Pipe With Catalytic Converter

1. Before removing any component of the exhaust system, always squirt a liquid rust dissolving agent onto the fasteners for ease of removal.
2. Raise and support the vehicle.
3. On some vehicles you will need to remove the brace from the transaxle.
4. Remove the exhaust pipe nuts from the manifold.
5. Support the catalytic converter pipe bolts from the rear of the converter.
6. Lower the catalytic converter/front pipe assembly from the vehicle. To install:
   
7. Be sure to use all new gaskets when required.
8. Attach the new catalytic converter/front pipe assembly to the vehicle. Tighten the pipe to manifold nuts to 20-40 ft. lbs. (27-55 Nm).
9. Attach the bolts at the rear of the catalytic converter/front pipe. Tighten them to 30-35 ft. lbs. (41-47 Nm).
10. Connect the brace at the transaxle if removed.
11. Lower the vehicle.

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

Removal & Installation 2.2L VIN 4 To Remove:

1. Drain the cooling system.
2. Remove the lower radiator hose from thermostat housing.
3. Remove the thermostat housing bolts and outlet.
4. Remove the thermostat.
5. Clean the mating surfaces.

To Install:

1. Install the thermostat.
2. Install the thermostat housing and bolts.
3. Install the coolant housing bolts. Tighten bolts to 14 Nm (10 ft. lbs.).
4. Install the lower radiator hose to thermostat housing.
5. Fill the cooling system.
6. Inspect for leaks.

2.2L VIN F 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. Tighten bolt to 10 Nm (18 in. lbs.).
   • Exhaust manifold. If equipped with an automatic transmission.
2. Fill the cooling system.

2.4L VIN T To Remove:

1. Drain the cooling system.
2. Remove the exhaust manifold heat shield bolts and shield.
   
   
   
   
3. Remove the coolant inlet housing bolts.
4. Lift vehicle.
5. Remove the coolant inlet housing stud from the oil pan.
6. Remove the wheel.
7. Remove the right engine splash shield.
8. Remove the transaxle-to-engine block brace bolts and brace.
9. Remove the radiator outlet pipe.
10. Remove the thermostat.
11. Clean the mating surfaces.

To Install:

1. Clean the mating surfaces.
2. Install the thermostat.
3. Install the radiator outlet pipe.
4. Install the transaxle-to-engine block brace and install bolts.
5. Install the right engine splash shield.
6. Install the wheel.
7. Lower the vehicle.
8. Install the exhaust manifold heat shield and bolt.
9. Tighten the exhaust manifold heat shield bolts to 14 Nm (10 ft. lbs.).
10. Fill the cooling system.
11. Inspect the system for leaks.

Removal & Installation 2.2L Engine To Remove:

1. Remove or disconnect the following:
   • Negative battery cable.
   • Heat shield.
   • Oxygen sensor.
2. Raise and safely support the vehicle.
3. Remove exhaust pipe from the exhaust manifold.
4. Lower the vehicle.
5. Remove the exhaust manifold mounting nuts from the cylinder head.
   
   
6. Remove the exhaust manifold.
7. Clean the mating surfaces.
8. Check for cracks, broken flanges and gasket surface damage.
9. Use a straight edge and a feeler gauge. If the flanges or the mating surfaces do not align, the manifold is warped and should be replaced.

To Install:
NOTE: The manufacturer recommends using new exhaust system nuts.

1. Install the manifold gasket.
2. Position the exhaust manifold to the cylinder head. Exhaust manifold 2.2L
   
   
3. Install the new exhaust manifold nuts. Tighten the nuts starting from the center and working toward the ends to 110 in lbs (12.5 Nm).
4. Raise and safely support the vehicle.
5. Install the exhaust pipe to the manifold using a new flex coupler gasket.
6. Install new exhaust flange mounting nuts.
   • Tighten to 33 ft lbs (45 Nm).
7. Lower the vehicle.
8. Install the oxygen sensor.
9. Install the heat shield.
10. Connect the negative battery cable.

2.4L Engine To Remove:

1. Disconnect the negative battery cable
2. Disconnect the Oxygen (O2) sensor electrical connector.
3. Remove the (O2) sensor.
4. Raise and safely support the vehicle. Exhaust brace 2.4L
   
   
5. Remove the exhaust manifold brace-to-manifold bolt and the oil pan nuts, if necessary. Exhaust heat shield 2.4L
   
   
6. Remove the upper heat shield. NOTE: Do NOT bend the exhaust flex decoupler more than necessary to remove it. Excessive movement will damage the flex decoupler
   Exhaust flex decoupler
   
   
7. Remove the manifold-to-exhaust flex decoupler fasteners.
8. Remove the exhaust pipe.
9. Carefully lower the vehicle.
10. Remove the exhaust manifold-to-cylinder head mounting nuts/bolts. Remove the exhaust manifold.
11. Discard the gaskets and/or seals. Clean the mating surfaces.

To Install:
Exhaust manifold 2.4L

1. Install new exhaust manifold gaskets. Position the exhaust manifold on the cylinder head. Tighten the mounting bolts in sequence to 110 in lbs (12.5 Nm).
2. Raise and safely support the vehicle.
3. Install the exhaust manifold heat shield. Tighten the mounting bolts to 10 ft. lbs (14 Nm).
4. Install the exhaust manifold brace-to-manifold bolt and the oil pan nuts. Tighten the mounting bolts to 41 ft lbs (56 Nm) and the nuts to 18 ft lbs (24 Nm).
5. Position the exhaust pipe to the manifold. Install the manifold-to-flex decoupler mounting bolts. Tighten to 26 ft lbs (35 Nm).
6. Lower the vehicle.
7. Coat the threads with a suitable anti-seize compound and install the O2 sensor.
8. Connect the O2 sensor electrical connector.
9. Connect the battery ground cable and check for leaks.

Regaurdless of which of the two exhaust manifolds you are attempting to replace it will be necessary to remove the exhaust manifold crossover pipe that lays over the top of the transmission and bridges the front and rear monifolds. Once this piece is out of the way you should be able to use a wrench or a rachet and socket to remove the bolts fastening the appropriate manifold to the cylinder head. Always remember to replace the exhaust manifold gasket as well.

Changing the oil pan gasket on a GMC Yukon XL is realtively simple, but does require removal of the exhaust pipe. You will need a new oil pan gasket and a new exhaust pipe flange gasket.
Put the car on ramps or jacks to access the undercarriage.
Remove the exhaust pipe by removing the 3 nuts holding the exhaust pipe flange to the exhaust manifold. These nuts often rust and prior application of penetrating oil may be required to remove them without damage. Once the pipe is unbolted, work the exhaust system loose from the hanging brackets. In most cases the entire system does not have to be removed since there is enough room to remove the pan with only the front hangers removed.
Drain the oil from the engine
Remove the 10 mm bolts holding the pan to the block.
Remove the old gasket material and scrape any remaining gasket from the block and pan.
Install the new gasket. Forma-Gasket or a similar product may be used in small quantities to "glue" the new gasket in place and prevent shifting while the pan is reattached to the block.
Reinsall the 10 mm bolts in a cross pattern to ensure the gasket is compressed evenly. Do not overtighten the bolts.
Replace the pipe to flange gasket between the exhaust pipe and the exhaust manifold with a new part.
Reattach the exhuast pipe to the hangers.
Install the 3 bolts connecting the pipe flange to the exhaust manifold.
Fill the engine with oil.

2.4L Engine

1. Disconnect the negative battery cable
   
2. Detach the Oxygen (O2) sensor electrical connector.
   
3. Properly drain the engine coolant into a suitable container. Remove the heater hose from the thermostat housing for a more complete coolant drain.
   
4. Remove upper exhaust manifold heat shield.
   
5. Remove the bolt that attaches the exhaust manifold brace to the manifold.
   
6. Remove the lower exhaust manifold heat shield.
   
7. Break the manifold-to-exhaust pipe spring loaded bolts loose using a 13mm box wrench.
   
8. Raise and safely support the vehicle.
   

NOTE It is necessary to relieve the spring pressure from 1 bolt prior to removing the second bolt. If the spring pressure is not relieved, it will cause the exhaust pipe to twist and bind up the bolt as it is removed.

1. Unfasten the two radiator outlet pipe-to-water pump cover bolts.
   
2. Remove the manifold to exhaust pipe bolts from the exhaust pipe flange as follows:
   
   1. Unscrew either bolt clockwise 4 turns.
      
   2. Remove the other bolt.
      
   3. Remove the first bolt.
      

NOTE DO NOT rotate the flex coupling more than 4° or damage may occur.

1. Pull down and back on the exhaust pipe to disengage it from the exhaust manifold bolts.
   
2. Remove the radiator outlet pipe from the oil pan and transaxle. Leave the lower radiator hose attached and pull down on the outlet pipe to remove it from the water pump. Leave the radiator outlet pipe hang.
   
3. Carefully lower the vehicle.
   
4. Unfasten the exhaust manifold-to-cylinder head retaining nuts, then remove the exhaust manifold, seals and gaskets.
   
5. Remove the front timing chain cover and the chain tensioner. For details, please refer to the procedure located later in this section.
   
6. Unfasten the water pump-to-cylinder block bolts. Remove the water pump-to-timing chain housing nuts. Remove the water pump and cover mounting bolts and nuts. Remove the water pump and cover as an assembly, then separate the two pieces.
   

Water pump and cover mounting—2.4L engine
Click to Enlarge To install:

1. Thoroughly clean and dry all mounting surfaces, bolts and bolt holes. Using a new gasket, install the water pump to the cover and tighten the bolts finger-tight.
   
2. Lubricate the splines of the water pump with clean grease and install the assembly to the engine using new gaskets. Install the mounting bolts and nuts finger-tight.
   
3. Lubricate the radiator outlet pipe O-ring with antifreeze and slide the pipe onto the water pump cover. Install the bolts finger-tight.
   
4. With all gaps closed, tighten the bolts, in the following sequence, to the proper values:
   
   1. Pump assembly-to-chain housing nuts:19 ft. lbs. (26 Nm).
      
   2. Pump cover-to-pump assembly: 106 inch lbs. (12 Nm).
      
   3. Cover-to-block, bottom bolt first: 19 ft. lbs. (26 Nm).
      
   4. Radiator outlet pipe assembly-to-pump cover: 125 inch lbs. (14 Nm).
      
5. Using new gaskets, install the exhaust manifold. Make sure to following the tightening sequence and torque specifications given in the exhaust manifold procedure located in this section.
   
6. Raise and safely support the vehicle.
   
7. Index the exhaust manifold bolts into the exhaust pipe flange.
   
8. Connect the exhaust pipe to the manifold. Install the exhaust pipe flange bolts evenly and gradually to avoid binding. Turn the bolts in until fully seated.
   
9. Connect the radiator outlet pipe to the transaxle and oil pan.
   
10. Install the timing chain tensioner and front cover.
    
11. Install the lower heat shield.
    
12. Carefully lower the vehicle.
    
13. Fasten the bolt that attaches the exhaust manifold brace to the manifold.
    
14. Tighten the manifold-to-exhaust pipe nuts to specification.
    
15. Install the upper heat shield.
    
16. Attach the oxygen sensor connector.
    
17. Fill the radiator with coolant until it comes out the heater hose outlet at the thermostat housing. Then connect the heater hose. Leave the radiator cap off.
    
18. Connect the negative battery cable, then start the engine. Run the vehicle until the thermostat opens, fill the radiator and recovery tank to their proper levels, then turn the engine OFF.
    
19. Once the vehicle has cooled, recheck the coolant level, then install the radiator cap.
    

3.1L Engine

1. Disconnect the negative battery cable.
   
2. Properly drain the cooling system into a suitable container.
   
3. Loosen, but do not remove, the water pump pulley bolts.
   
4. Remove the serpentine belt.
   
5. Unfasten the water pump pulley bolts, then remove the pulley.
   
6. Remove the five water pump mounting bolts, then remove the water pump.
   

To install:
View of the water pump mounting and bolt tightening specifications—3.1L engine shown
Click to Enlarge

1. Clean all the gasket surfaces completely.
   
2. Apply a thin bead of sealer around the outside edge of the water pump along the gasket sealing area, then install the gasket onto the water pump.
   
3. Position the water pump on the engine, then tighten the water pump mounting bolts to 89 inch lbs. (10 Nm).
   
4. Install the water pump pulley and finger-tighten the pulley bolts.
   
5. Install the serpentine belt.
   
6. Tighten the water pump pulley bolts to 18 ft. lbs. (25 Nm).
   
7. Fill the cooling system.
   
8. Connect the negative battery cable, then start the engine. Let the engine run until it reaches normal operating temperature, then check for leaks and coolant level. Add coolant, if necessary, then turn the engine OFF.