* Intake Manifold Problems: Cracked or warped intake manifolds are a frequent problem. This can lead to vacuum leaks, rough running, and reduced power. The plastic used wasn't ideal for the temperature cycling.
* Exhaust Manifold Issues: Similar to the intake manifold, the exhaust manifolds can crack, especially around the collector area due to heat cycling. This can lead to exhaust leaks, reduced performance, and potential catalytic converter damage.
* Head Gasket Failure: Though less common than in some other engines, head gasket failure can still occur, particularly due to overheating or prolonged neglect. Symptoms include coolant leaks, white smoke from the exhaust, and loss of compression.
* Roller Lifter Issues: These engines use roller lifters, which can experience premature wear, especially if the oil isn't changed regularly or if low-quality oil is used. This can lead to lifter tick, noisy valve train, and potentially camshaft damage.
* Cooling System Issues: Problems with the cooling system, including water pump failure, thermostat issues, or radiator leaks, can lead to overheating, which can damage the engine significantly. These are common across all engines, not just the Vortec.
* Oil Pressure Issues: Potential problems with the oil pump or sending unit can lead to low oil pressure, which is catastrophic for engine health. This can be due to age, wear, or improper maintenance.
* Crankshaft Position Sensor (CKP) issues: This sensor is crucial for engine timing. A faulty sensor can lead to no-start conditions, misfires, and rough running.
* Variable Valve Timing (VVT) system issues: While not as common in '99 models (some VVT systems came later), potential issues with the solenoids or the VVT system itself could occur, affecting performance and fuel efficiency.
It's crucial to remember that proper maintenance, including regular oil changes with quality oil, using the correct coolant, and addressing any issues promptly, significantly reduces the likelihood of encountering these problems. A well-maintained 5.7L Vortec can last for many years and miles.
