Your chainsaw often leaks bar oil while it's sitting idle primarily due to atmospheric pressure changes and other potential issues with the oiling system.
Understanding why your chainsaw leaks bar oil when it's not running involves looking at how the oiling system is designed and how external factors can affect it.
The Primary Cause: Atmospheric Pressure
One significant reason for bar oil leakage during storage, as highlighted by experts, is related to atmospheric conditions.
- Pressure Variations: Normal fluctuations in air pressure occur throughout the day and night, often triggered by changes in temperature.
- Effect on Tank: These pressure variations can create differences in pressure between the inside of the bar oil tank and the outside atmosphere.
- Forcing Oil Out: In some atmospheric conditions, the oil may be forced out of the tank through the oil pump while the chainsaw is in storage. This happens because the increased pressure inside the tank (relative to the outside) pushes the oil outwards through the path of least resistance, which is typically the oil pump outlet feeding the bar and chain.
This is a common phenomenon, especially if the tank is full and the saw is stored in a location with noticeable temperature swings.
Other Potential Reasons for Leaking
While atmospheric pressure is a key factor for leaks when not in use, other issues can also contribute.
- Loose or Damaged Cap: The bar oil reservoir cap needs a good seal. If it's loose, cracked, or the O-ring is damaged, oil can seep out, especially if the saw is tilted.
- Cracked Tank or Oil Line: Damage to the plastic oil tank or the hoses leading from the tank to the pump can cause leaks.
- Issues with the Oil Pump: While the reference focuses on pressure pushing oil through the pump, internal pump issues, seals, or fittings could also be a source of leaks when idle, though less common than pressure-induced leaks.
- Blocked Vent: The oil tank usually has a vent to equalize pressure. If this vent is blocked, it can sometimes contribute to pressure issues, although it's more often associated with oil not flowing correctly during use.
Preventing Bar Oil Leaks
Here are a few practical steps you can take to minimize or prevent bar oil leaks during storage:
- Empty the Tank: The most effective way is to drain the bar oil tank before storing the chainsaw for an extended period. Run the saw briefly after draining to clear residual oil from the pump and line (do this over cardboard or a tray).
- Store on Absorbent Material: Always store your chainsaw on cardboard, an old rag, or a drip tray to catch any minor leaks.
- Check the Oil Cap: Ensure the bar oil cap is securely tightened and that the seal or O-ring is in good condition. Replace if necessary.
- Inspect the Saw: Periodically check the tank, hoses, and around the pump area for visible cracks or damage.
- Consider Storage Location: While not always practical, storing the saw in a location with stable temperature might reduce pressure variations.
By understanding that atmospheric pressure changes, caused by normal variations in air pressure that occur due to changes in temperature throughout the day and night, are a key reason oil can be forced out via the oil pump while the chainsaw is in storage, you can better manage and prevent leaks.
