Performance Oil Pump Timing Chain & Water Pump Kit for GMC Sierra 1500 (1999-2004) 5.3L

High-Durability Oil Pump, Timing Chain & Water Pump Refresh Kit for 1999-2004 GMC Sierra 1500 (GMT800)

What it Does: The Performance Oil Pump, Timing Chain & Water Pump Kit restores critical oil pressure, cam timing accuracy, and coolant circulation on the 1999-2004 GMC Sierra 1500 to prevent oil starvation, timing slack, and overheating under load.

The Stock GMC Sierra 1500 Front-Drive & Timing Weakness

Factory high-mileage Vortec 5300 engines suffer from progressive timing chain elongation, which degrades cam timing advance and causes cam sensor correlation codes. Concurrently, factory GM LM7 oil pump bypass valves are prone to sticking, while internal gerotor cavitation under sustained RPM drops idle oil pressure below safe operational thresholds. Paired with aged water pump bearing fatigue and leaking shaft packings, high-heat towing cycles accelerate timing cover seal degradation and risk severe engine bearing wash.

The Engineering Solution

This front-engine overhaul assembly pairs a precision-machined oil pump featuring tightly toleranced internal rotors for stable oil pressure delivery across the entire rev range with a pre-stretched, heavy-duty link-belt timing chain and induction-hardened crank/cam sprockets. The replacement water pump incorporates an anti-cavitation impeller and premium ceramic-face mechanical seal to resist high thermal loads. Complete with a front cover gasket and crank seal package, this kit locks down cam phasing and oil supply integrity under heavy-duty truck usage.

What's Included

• 1 Oil Pump
• 1 Timing Chain Kit (chain and sprockets)
• 1 Timing Cover Gasket Set
• 1 Water Pump
• Assorted seals and O-rings

Technical Specifications

Compatibility

• 1999-2004 GMC Sierra 1500 5.3L V8 (Vortec 5300 OHV)
• Fits GM Gen III Small Block V8 applications (4.8L, 5.3L, 6.0L Vortec platforms)

Frequently Asked Questions & Fitment Warnings

Does this fit the GMT800 Sierra 1500?

Yes, this is a direct fit for the 1999-2004 GMC Sierra 1500 equipped with the 5.3L Vortec LM7/L59 engine. Verify your engine displacement and configuration before ordering; not compatible with Gen IV engines with displacement-on-demand or variable valve timing.

Do I need to prime the oil pump prior to first startup?

Yes, pack or thoroughly prime the oil pump cavity with clean engine oil or assembly lubricant prior to timing cover installation to help ensure immediate lubrication pickup and prevent dry-start wear.

The GMC Heavy-Haul Standard

Constructed to endure severe duty cycles, continuous payload hauling, and high-heat trailering demands, this comprehensive front-end service assembly delivers dependable oiling, timing accuracy, and thermal control for your GMT800 platform.