Crankshaft seals are designed to keep fluid in and dirt or contaminants out. As the engine ages due to hours and mileage, the crankshaft seal ages as well.
There are two types of crankshaft seals
- Front cover seal (front of crankshaft)
- Rear main seal (rear of crankshaft)
Front cover seal
The most common seal that wears out and needs replaced is a front cover seal. This seal resides in the front housing that covers a timing chain or timing belt. This seal usually gets the most abuse due to the pressure of the timing chain or timing belt and the accessories driven by the serpentine belt or v-belt.
This seal can be tricky to replace, especially if it is in a transverse engine, meaning a front wheel drive or all wheel drive mounted engine.
On a rear wheel drive vehicle, the seal replacement can be easy or difficult depending on what needs to be removed to take the cover off of the engine. For vehicles with camshaft in the block, the cover is relatively small and usually has easy access. On the other hand, vehicles with overhead camshafts of one or more or even dual heads with overhead camshafts can be difficult when changing out a seal.
Even on a transverse mounted engine, the seal removal can be tricky due to the lack of room to access the seal. This makes it harder to remove and replace the seal with using greater efforts.
When it comes to replacing the seal, the only thing to do is see if the seal is mounted from the inside of the cover or the outside of the cover. If the seal is mounted from the inside of the cover, then the front cover must be removed to replace the seal. However, if the seal is mounted on the outside of the front cover, then using a seal remover tool and removing the harmonic balancer will allow the seal removal process to be successful in a shorter amount of time and less effort.
For some vehicles, the water pump or power steering pump may be in the way of the mounting bolts to the front cover seal. This makes the seal removal process even more time consuming due to having to remove the additional components to gain access to the mounting hardware.
If the front cover was removed to install a new front cover seal, be sure to clean the inside of the cover and the gasket flange area. Clean parts ensure the engine is to be non contaminated and kept in good condition. Cleaning the gasket flange area will prevent any oil leakage during engine operation after replacing the front cover seal.
Rear main seal
The rear main seal is the most difficult seal to replace on an engine. This seal resides on the back of the crankshaft and is between the engine and transmission. It is required to remove the transmission to replace the rear main seal.
- Note: When changing a clutch or a torque converter, it is recommended to replace the rear main seal.
If you need to replace your front crankshaft seal or need other service performed, contact one of our YourMechanic’s automotive specialists and we’d be happy to help.
This article originally appeared on YourMechanic.com as Why Crankshaft Seal Replacements Can Be Tricky and was authored by Marvin Sunderland.