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.
SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 162 (ENGINE CONTROLS - SYSTEM & COMPONENT TESTS - 2.2L)EMISSION SYSTEMS & SUB-SYSTEMSPOSITIVE CRANKCASE VENTILATIONINSPECTION/DIAGNOSIS
1999 GMC Forward Control 5.7 R, Automatic
Positive Crankcase Ventilation: Inspection/Diagnosis
1999 GMC Forward Control 5.7 R, AutomaticSECTION Inspection/Diagnosis
WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
- Disconnect the PCV hose.
- Start the engine.
- Check for vacuum at the hose. If there is no vacuum, check for a plugged hose or manifold port. Check for a hose that collapses when blocked (vacuum applied). Replace the plugged or the deteriorated hoses.
- Allow the engine to idle at normal operating temperature.
- Remove the engine oil dipstick and install a vacuum gauge on the dipstick tube.
- Block off the PCV system fresh air intake passage.
- Run the engine at 1500 RPM for 30 seconds, then read vacuum gauge while engine is running at 1500 RPM.
- If vacuum is present, this indicates that the crankcase ventilation system is functioning properly.
- If no vacuum is indicated, the engine may not be sealed and is drawing in outside air. Check the valve covers, the oil pan gasket or other sealing areas for leaks. See appropriate article in ENGINES.
- If the vacuum gauge registers a pressure, or if a vacuum gauge is pushed out of dipstick tube, check for a plugged PCV port, a plugged hose or an excessive engine blow-by.
RENDER: 1.0x
NO RELATED
Recommended Tools & Savings
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.