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Autopapyrus · Hummer H2 6.0 V8 LQ4 (2007)
https://autopapyrus.com/guides/hummer/h2/oil-pump-replacement/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Hummer H2 6.0 V8 LQ4 (2007): Oil Pump Replacement

On the LQ4, the gear-type oil pump sits in the front engine cover and is driven directly by the crankshaft nose. The pump rarely fails on its own, so before replacing it, use a mechanical gauge to confirm that the pump is the cause of the low pressure and not worn bearings, a clogged pickup tube or a faulty sender. The job requires removing the accessory drive and harmonic balancer, and lowering or removing the oil pan.

Difficulty: Hard Time: 8-14 hours (up to two days if you have no experience) Steps: 18 Tools: socket and ratchet set, torque wrench (10-250 N·m range), harmonic balancer puller, harmonic balancer installer tool (or a 36-38 mm wrench/socket for the center bolt), lift or pit, jacks and jack stands, drain pans for oil and coolant, gasket scraper, sealant for oil pan joints, serpentine belt tool

Part

  • 🔩 oil pump complete with front engine cover (on Gen III Vortec 6000 family engines the pump is integrated into the front cover), front cover gasket, front crankshaft seal, oil pan gasket (or gasket set), oil filter, 5W-30 engine oil (about 6 L (6.3 qt)), coolant, water pump gasket/seal if needed. Pump and cover prices vary by manufacturer, so check with your supplier

Step by step

18 steps
  1. Diagnose before disassembly. Install a mechanical gauge in place of the oil pressure sender. For a warm engine at idle, expect at least 0.4-0.6 bar at minimum rpm and noticeably higher at 2000-3000 rpm. Check the exact values against the manufacturer's specification. Low pressure with a good sender and clean oil points to the pump or engine wear.
  2. Disconnect the negative battery terminal. Lift the vehicle and secure it firmly on jack stands. Remove the skid plate if fitted.
  3. Drain the engine oil and coolant, and remove the oil filter. Collect the drained coolant for reuse or proper disposal.
  4. Remove the air intake duct and resonator, the electric fan with shroud, and if necessary the radiator (or at least move it forward). This gives you access to the front of the engine. Photograph the routing of hoses and connectors.
  5. Release the tension and remove the serpentine belt. Remove the tensioner, and if necessary the alternator, A/C compressor and power steering pump, moving them aside without disconnecting the A/C lines.
  6. Remove the water pump. It mounts on the same front cover. Replace the seal, and replace the pump itself if the bearing is worn or it leaks.
  7. Remove the harmonic balancer. The center bolt is very tight, so keep the balancer from turning. Remove the balancer only with a puller, pulling on the hub and not on the outer rim.
  8. Lower the oil pan. The front cover is bolted partly to the oil pan flange, so the pan must be loosened or removed. Depending on the pan version, you may need to disconnect the front axle or support the engine with a jack. Carefully separate the gasket from the pan and block.
  9. Remove the front cover bolts, and note their length and location. Remove the cover by tapping lightly on the lugs with a mallet. Do not pry with a screwdriver on the mating surface.
  10. Inspect the pump gears, the cover face and the crankshaft nose for scoring, wear and scratches. Check the pickup tube and screen for deposits. If there are metal shavings or metallic dust in the oil, the cause is in the engine itself, and replacing the pump alone will not fix it.
  11. Clean the mating surfaces of the block, cover and oil pan of any gasket and sealant residue, and degrease them. Install a new seal in the cover, lubricating the lip with oil. Press it in straight, without cocking it.
  12. Before installation, fill the pump with clean engine oil or pack it with petroleum jelly to fill the cavities. Otherwise the pump may not build pressure at first start.
  13. Install the new gasket and the cover. Center it on the seal using an alignment tool or the balancer itself, and tighten the cover bolts evenly in a crisscross pattern. Torque values for the cover bolts are low: about 10-25 N·m (7-18 lb-ft) depending on bolt size (check the exact values in the service manual).
  14. Install the oil pan with a new gasket and tighten the bolts evenly in several passes, not exceeding 10-25 N·m (7-18 lb-ft) for the pan bolts per the service manual. Clean the joints and apply sealant where the design calls for it.
  15. Install the balancer using an installer tool, not by hammering. The balancer center bolt is specified at a very high torque, or a torque plus an angle (on some versions the bolt is single-use). Use a new bolt and tighten it to the manufacturer's specification.
  16. Install the water pump, alternator, compressor, power steering pump, tensioner and belt. Install the radiator, fan and hoses.
  17. Install a new oil filter, add oil, and fill the cooling system. Before starting, crank the engine with the starter with the fuel supply disabled (or the spark plugs removed) until oil pressure shows on the gauge cluster or the mechanical gauge.
  18. Start the engine and immediately check the oil pressure and look for leaks at the cover, oil pan and seal. Warm it up, bleed the air from the cooling system and check the fluid levels. After 100-200 km, check again for leaks.

Common mistakes and warnings

  • If you find metal shavings in the oil or signs of bearing wear, replacing the pump will not solve the problem. Driving with low oil pressure quickly destroys an engine, so do not drive the vehicle until the cause is fixed. This is a difficult job that requires exact balancer torque and proper sealing of the cover, so if you lack experience, leave it to a repair shop. The vehicle is heavy, so work only on solid jack stands, never under a jack alone. The airbags are not affected, but disconnecting the battery is mandatory before working near the alternator and starter.