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John
John, GMC Technician
Category: GM
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Experience:  ASE MASTER TECHNICIAN/40 years experience
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1986 GMC: I find, and how do I change, the oil pump..block

Customer Question

WHere do I find, and how do I change, the oil pump on a 1986 GMC 454 block engine?
Submitted: 6 years ago.
Category: GM
Expert:  John replied 6 years ago.

Hello & Welcome to JA,

 

Here is information to help you. The oil pump is inside the oil pan.

Gasoline V8 and V6 Engines

See Figures 1, 2, 3 and 4

  1. Disconnect the negative battery cable. Remove the air cleaner assembly, as required. Remove the distributor cap, if necessary.
  2. Raise the vehicle and support it safely. Be sure to support the vehicle of jackstands at a sufficient height to allow ground clearance with the entire length of the oil pan as it will have to be tilted almost vertically for removal.
  3. Drain the engine oil, then remove the flywheel cover and the starter assembly.




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Fig. Fig. 1: The starter assembly and flywheel cover must be removed for access.



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Fig. Fig. 2: Loosen and remove the oil pan bolts using a ratchet, extension and suitable socket

  1. On some vehicles equipped with V6 engine, remove the strut rods at the flywheel cover, as necessary.
  2. On 4WD vehicles with automatic transmission, remove the strut rods at the engine mounts.
  3. On vehicles equipped with gages, remove the oil pressure line from the side of the engine block to avoid damage when raising the engine. If necessary, remove the oil filter.



CAUTION Take extreme caution if the engine must be raised to remove the oil pan. Make sure the engine lift or hydraulic jack is firmly set. If at all possible, block the engine in this position using wooden blocks between the engine block or engine mounts and jackstands or the vehicle frame rail.

  1. On most vehicles it will be necessary to raise the engine in order to gain clearance for oil pan removal. If necessary, carefully jack the engine slightly using a block of wood under the transmission tail Section or using a engine lift. If additional clearance is necessary, remove the engine mount through-bolts before raising the engine. Remove the oil pan retaining bolts.




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Fig. Fig. 3: Pivot the oil pan rearward and begin to pull it down



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Fig. Fig. 4: Once the pan clears the engine and the lower crossmember you will be free to remove it from the vehicle

  1. Pivot the oil pan downward and the rear and carefully lower it from the engine.
  2. Installation is the reverse of the removal procedure. Use new gaskets or RTV sealant, as required. On the V6 engine torque the pan retaining bolts to 100 inch lbs. On the small block V8 engines torque the bolts to 100 inch lbs. and the nuts to 200 inch lbs. On some 350 engines so equipped, torque the oil pan baffle bolts to 26 ft. lbs. On the 454 V8 engine torque the pan to front cover to 70 in. lbs. and the pan to block to 135 inch lbs.

REMOVAL & INSTALLATION

 

See Figures 1 and 2

The oil pump is mounted to the bottom of the block and is accessible only by removing the oil pan.

  1. On all engines, including diesel, remove the oil pan.
  2. Unbolt and remove the oil pump and screen as an assembly. On the in-line sixes, remove the flange mounting bolts and nut from the elongated number 6 main bearing cap bolt, then remove the pump.


To install:

  1. Prime the pump with clean motor oil.
  2. Align the oil pump drive shaft on the in-line 6 cylinder engines to match with the distributor tang and position the pump flange over the distributor lower bushing. Install the pump mounting bolts.
  3. On V6 and V8 engines, insert the drive shaft extension through the opening in the main bearing cap until the shaft mates with the distributor drive gear. You may have to turn the drive shaft extension one way or the other to get the two to mesh. Position the pump on the cap and install the attaching bolts.
  4. Install the oil pans on all engines.




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Fig. Fig. 1: Oil pump installation



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Fig. Fig. 2: Oil pump exploded view