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.
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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 234 (ENGINE CONTROLS - REMOVAL & INSTALLATION)AIR INDUCTION SYSTEMSINTAKE MANIFOLDCLEANING & INSPECTION
1999 GMC Forward Control 5.7 R, Automatic
Cleaning & Inspection
1999 GMC Forward Control 5.7 R, AutomaticSECTION Cleaning & Inspection
WARNING: This page is about a different car, the 2003 Cadillac Seville and 2003 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
WARNING:
Wear safety glasses in order to avoid eye damage.
- Do not reuse the intake manifold-to-cylinder head sealing gaskets. Remove any remaining gasket and/or gasket material from the intake manifold. Clean the intake manifold gasket grooves, intake manifold passages, PCV vacuum hose passage and vacuum hose fitting passage in solvent.
- Dry the intake manifold with compressed air. Inspect the intake manifold for damage to the fuel rail mounting inserts and damage to the studs. See Fig 1.
- Inspect the intake manifold for damage to the intake manifold bolt bosses, or cracks to the composite intake manifold assembly and damage in areas between the intake runners. See Fig 2.
- Inspect the intake manifold for gouges or cracks to the intake manifold sealing surfaces and grooves and excessive scoring to the fuel injector bores. See Fig 3. Inspect the front of the intake manifold for debris or restrictions to the intake manifold passage and damage to the plenum duct neck.
- Inspect the intake manifold for debris or restrictions to the PCV system hose port and debris or restrictions to the vacuum port.
- Inspect the intake manifold cylinder head deck for warpage. Locate a straight edge across the intake manifold cylinder head deck surface. Insert a feeler gauge between the intake manifold and the straight edge. An intake manifold with warpage in excess of 0.010 in per 1.00 in (0.25 mm per 25 mm) must be replaced. Repair or replace the intake manifold as necessary.
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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.