Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2003 Hummer H2 V8-6.0LFACTORY OEM SERVICE PROCEDURE
System Specifications
Cylinder Head Surface Variation
Surface Flatness - Block Deck Measured Within a 152.4 mm (6.0 in) Area 0.08 mm (0.003 in)
Surface Flatness - Block Deck - Measuring the Overall Length of the Cylinder Head 0.1 mm (0.004 in)
Surface Flatness - Exhaust Manifold Deck 0.13 mm (0.005 in)
Surface Flatness - Intake Manifold Deck 0.08 mm (0.0031 in)
USE NEW CYLINDER HEAD BOLTS
Cylinder Head Bolts - First Pass all M11 Bolts in Sequence 30 N.m (22 lb ft)
Cylinder Head Bolts - Second Pass all M11 Bolts in Sequence 90 degrees
Cylinder Head Bolts -Final Pass all M11 Bolts in Sequence - Excluding the Medium Length Bolts at the Front and Rear of Each Cylinder Head 90 degrees
Cylinder Head Bolts - Final Pass M11 Medium Length Bolts at the Front and Rear of Each Cylinder Head in Sequence 50 degrees
Cylinder Head Bolts - M8 Inner Bolts in Sequence 30 N.m (22 lb ft)
Cylinder Head Coolant Plug 20 N.m (15 lb ft)
Intake Manifold Surface Variation
Surface Flatness - Measured at Gasket Sealing Surfaces and Measured Within a 200 mm (7.87 in) Area that Includes Two Runner Port Openings 0.3 mm (0.118 in)
Intake Manifold Bolts - First Pass in Sequence 5 N.m (44 lb in)
Intake Manifold Bolts - Final Pass in Sequence 10 N.m (89 lb in)
Intake Manifold Wiring Harness Stud 10 N.m (89 lb in)
Exhaust Manifold Bolts-First Pass 15 N.m (11 lb ft)
Exhaust Manifold Bolts-Final Pass 25 N.m (18 lb ft)
Exhaust Manifold Heat Shield Bolts 9 N.m (80 lb in)
Surface Flatness - Block Deck Measured Within a 152.4 mm (6.0 in) Area 0.08 mm (0.003 in)
Surface Flatness - Block Deck - Measuring the Overall Length of the Cylinder Head 0.1 mm (0.004 in)
Surface Flatness - Exhaust Manifold Deck 0.13 mm (0.005 in)
Surface Flatness - Intake Manifold Deck 0.08 mm (0.0031 in)
Cylinder Head Tightening Sequence:
USE NEW CYLINDER HEAD BOLTS
Cylinder Head Bolts - First Pass all M11 Bolts in Sequence 30 N.m (22 lb ft)
Cylinder Head Bolts - Second Pass all M11 Bolts in Sequence 90 degrees
Cylinder Head Bolts -Final Pass all M11 Bolts in Sequence - Excluding the Medium Length Bolts at the Front and Rear of Each Cylinder Head 90 degrees
Cylinder Head Bolts - Final Pass M11 Medium Length Bolts at the Front and Rear of Each Cylinder Head in Sequence 50 degrees
Cylinder Head Bolts - M8 Inner Bolts in Sequence 30 N.m (22 lb ft)
Cylinder Head Coolant Plug 20 N.m (15 lb ft)
Intake Manifold Surface Variation
Surface Flatness - Measured at Gasket Sealing Surfaces and Measured Within a 200 mm (7.87 in) Area that Includes Two Runner Port Openings 0.3 mm (0.118 in)
Intake Manifold Tightening Sequence:
Intake Manifold Bolts - First Pass in Sequence 5 N.m (44 lb in)
Intake Manifold Bolts - Final Pass in Sequence 10 N.m (89 lb in)
Intake Manifold Wiring Harness Stud 10 N.m (89 lb in)
Exhaust Manifold Bolts-First Pass 15 N.m (11 lb ft)
Exhaust Manifold Bolts-Final Pass 25 N.m (18 lb ft)
Exhaust Manifold Heat Shield Bolts 9 N.m (80 lb in)
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.