Required tools and materials:
- Oil drain pan
- Wrench set
- Screwdriver
- New oil pump and gasket
- Oil filter
- New engine oil (check your vehicle's manual for the recommended type and amount)
- Funnel
- Rags
Steps to replace the oil pump:
1. Prepare the vehicle. Park it on a level surface, engage the parking brake, and allow the engine to cool down completely.
2. Locate the oil drain plug. It's usually located on the bottom of the oil pan. Place the oil drain pan beneath the drain plug.
3. Drain the oil. Use a wrench to loosen the drain plug and allow the old oil to drain completely into the oil pan.
4. Remove the oil filter. It's typically located near the top of the engine. Use an oil filter wrench to loosen and remove it.
5. Remove the oil pump. The oil pump is usually located on the front of the engine block, near the bottom. Disconnect any hoses or wires attached to the oil pump. Then, use a wrench to loosen and remove the bolts that hold the oil pump in place. Be careful not to drop the bolts into the oil pan.
6. Clean the mating surfaces. Use a rag to clean the mating surfaces on the engine block and the oil pump. This will ensure a good seal when installing the new oil pump.
7. Install the new oil pump gasket. Place the new gasket on the mating surface of the engine block. Make sure it's seated properly.
8. Install the new oil pump. Carefully lift the new oil pump into place and align it with the gasket. Secure it by tightening the bolts in a crisscross pattern to prevent warping.
9. Reconnect hoses and wires. Reconnect any hoses or wires that you disconnected from the oil pump.
10. Replace the oil filter. Screw on a new oil filter by hand until it's snug. Do not over-tighten.
11. Replace the oil drain plug. Reinstall the oil drain plug and tighten it securely.
12. Add new engine oil. Use a funnel to add the recommended amount of new engine oil to the engine. Check the oil level using the dipstick.
13. Start the engine and let it run for a few minutes. This will circulate the new oil throughout the engine and build up oil pressure.
14. Check for leaks. Look under the vehicle for any oil leaks. If you see any leaks, tighten the bolts that secure the oil pump or the oil filter until the leak stops.
That should replace the oil pump on your Pontiac 400 engine. Remember, if you're not confident performing this task, it's always best to consult a professional mechanic.
