Priming an engine oil system involves circulating oil throughout the engine's internal passages and bearings before the engine is started, ensuring immediate lubrication upon ignition. This crucial step prevents dry starts, which can cause significant wear and damage, especially to newly built or rebuilt engines.
Why Engine Oil Priming is Essential
A properly primed oil system guarantees that all critical engine components, such as bearings, camshafts, and lifters, receive immediate lubrication. This is particularly vital for:
- New Engine Builds: After assembly, oil passages are completely dry. Priming coats all surfaces with oil, preparing them for the initial start-up and break-in period.
- Engine Rebuilds: Similar to new builds, rebuilt engines have dry components that need pre-lubrication.
- Engines That Have Sat for Extended Periods: Over time, oil can drain completely from upper engine components, leaving them vulnerable to wear on the first start.
- After Major Oil System Work: If the oil pump, oil cooler, or extensive oil lines have been replaced or disconnected, priming ensures the system is full and air-free.
| Benefit of Priming | Description |
|---|---|
| Prevents Dry Starts | Delivers oil to all critical components before the engine fires. |
| Reduces Wear | Minimizes metal-on-metal friction during the crucial initial moments. |
| Extends Engine Life | Protects components from premature damage. |
| Ensures Oil Pressure | Confirms the oil pump is functioning and the system is full of oil. |
| Optimizes Break-In | Prepares new components for the demanding break-in process. |
How to Prime an Engine Oil System
Priming an engine oil system is a straightforward process that typically involves manually forcing oil through the system.
1. Prepare the Engine and Oil
- Fill the Oil Pan: Begin by filling the engine's oil pan with the appropriate amount and type of oil. For new or rebuilt engines, it's highly recommended to use a quality break-in oil designed to facilitate proper ring seating and protect new components.
- Check Filters: Ensure the oil filter is correctly installed and filled with oil (if applicable for your filter type).
2. Choose Your Priming Method
There are two primary methods for effectively priming an engine oil system:
A. Using an Oil Pump Priming Tool and Power Drill
This is the most common and effective method for many engines, especially those with cam-driven oil pumps.
- Locate the Oil Pump Drive: On many engines, the oil pump is driven by the distributor shaft or a dedicated drive shaft. You will need to remove the distributor (or the oil pump drive plug, depending on engine design) to access the oil pump's drive gear.
- Insert the Priming Tool: A specialized oil pump priming tool is designed to engage the oil pump's drive gear. Insert this tool into the oil pump drive opening.
- Attach Power Drill: Connect a powerful power drill (corded is often preferred for consistent torque) to the top of the priming tool.
- Activate and Rotate: With the drill set to a low or moderate speed, begin turning the oil pump with the power drill and priming tool. As you do this, rotate the crankshaft by hand periodically. This can be done by turning the harmonic balancer bolt or by engaging the flywheel. Rotating the crankshaft allows the lifters to move, the camshaft to turn, and all the bearings to align differently, ensuring that oil gets around all the bearings and into all the internal oil passages, fully lubricating all components.
- Monitor Oil Pressure: Watch the engine's oil pressure gauge (if installed) or an external pressure gauge connected to a suitable port. You should see oil pressure build up. Continue priming until steady oil pressure is observed, and you can confirm oil has reached the top of the engine (e.g., through rocker arm oiling).
B. Using an External Engine Preluber
An external engine preluber is a dedicated tool that uses an external reservoir and pump to force oil into the engine's oil gallery.
- Connect Preluber: Connect the preluber's hose to an accessible oil gallery port on the engine (often near the oil pressure sending unit or an oil cooler port).
- Fill Preluber: Fill the preluber's reservoir with the appropriate engine oil.
- Pressurize System: Activate the preluber, which will pump oil into the engine's oil passages. Similar to the drill method, rotate the crankshaft by hand while the system is being pressurized. This ensures oil reaches all areas and surfaces of the bearings and other components.
- Monitor Pressure: Observe the preluber's gauge or the engine's oil pressure gauge to confirm proper oil pressure buildup. Continue until oil reaches the upper engine components.
3. Verify Lubrication
- Visually confirm that oil is flowing to the rocker arms or other upper engine components. This can often be done by observing through the oil fill cap or by temporarily removing a valve cover.
- Ensure the oil pressure gauge registers a stable reading.
Final Steps Before Starting
- Once priming is complete, remove any priming tools or preluber connections.
- Reinstall the distributor or oil pump drive plug, ensuring proper timing if applicable.
- Top off the engine oil if necessary.
- The engine is now ready for its initial start-up, with all critical components pre-lubricated for a safe and controlled beginning.
