Introduction
A crankshaft seal located at the front and rear of your car's engine, and is designed to control motor oil from leaking as the engine is running and the crankshaft is turning. There are two main seals, the front seal which is located in the timing chain cover or front seal plate, and the rear main seal which is located at the rear of the engine block mounted within the seal plate which also bolts to the oil pan. In this guide, we will cover the detailed symptoms of a front main seal leak and how to diagnose it.
Common Symptoms of a Crankshaft Main Seal Leak
1. Visible Oil Leaks Near the Front or Rear of the Engine
The most common symptoms of an main shaft oil leak is obviously, oil leakage. Raise the front of the car up and use a flashlight to confirm the oil leakage is coming from the front or rear seals. Though you might find oil leakage in a particular area, you will not be able to see the "rear" main seal directly, but most of the time the front seal is visible. If the rear main seal is leaking oil will drip from the transmission bell housing.
If the front seal is leaking you will be able to see oil dripping from the crankshaft pulley, harmonic balancer, or timing cover. If the leak continues, it will affect the serpentine belts ability to perform and you will lose water pump, alternator or AC compressor operations. If the problem is further neglected, oil will begin to saturate the cooling hoses and cause a coolant leaks which will cause engine overheating.
2. Low Engine Oil Levels
Because the main seal are low on the engine, motor oil can leak out rather quickly and if left unattended it will cause oil warning light to come on and damage the engine.
3. Oil on the Underside of the Engine
Oil leaking from the front main seal can accumulate on the oil pan, engine mounts, and other components beneath the engine. This can lead to excessive oil buildup and contamination of other engine parts.
4. Burning Oil Smell
You might notice a burning smell from inside the car as you drive, this is because oil may leak onto the exhaust system where it is burned and in extreme cases it can cause a fire.
5. External Symptoms
A main seal oil leak will stain your driveway and garage floor as oil drips once the engine is off and the car is stationary.
Conclusion
If you have found crankshaft seal leakage, check above the seal location to confirm there is no leakage above which can simulate the seal failure falsely.
Causes of a Crankshaft Main Seal Leak
- Natural wear and tear due to age
- Excessive crankshaft end play
- Incorrect installation of the seal
- Hardened or cracked seal material
- Excessive heat leading to seal degradation
- High engine pressure due to a clogged PCV valve
- Over filled engine oil levels
Credits
This guide knowledge base was created by the 2CarPros Team, and by Ken Lavacot: Automobile repair shop owner and certified master automobile technician of over 30 years. If you have question or need help please ask one of our experts we are happy to help. Please visit our 2CarPros YouTube Channel.
Article published 2025-02-20
