What to know about the Front Crankshaft Seal:

A number of mechanisms must operate together to make your vehicle move forward. One of the most essential is the crankshaft, which converts rotary into linear motion; i.e., it transforms the force created by the engine’s pistons moving up and down into a force that moves in a circular motion that causes a car’s wheel to turn. Surrounded by what’s called a crankcase—the largest cavity in the engine block, just underneath the cylinders—the crankshaft must be completely lubricated, essentially submerged in oil, to spin nearly friction-free and do its job properly.

Consequently, there are seals situated at either end of the crankshaft that permit it to spin freely and keep engine oil from escaping the engine block, as well as stop contaminants and other debris from entering and causing damage to the mechanism. Since there are two ends of the crankshaft, there are two types of seals: the front crankshaft seal and the rear crankshaft seal, also known as the front main and rear main seals.

Facts to Note:


Loss of oil will eventually cause serious internal engine damage.

Examine the sealing surface of the crankshaft or the crankshaft pulley (depending on the engine design) for damage when changing the crankshaft seal.

Oil degrades rubber parts.

How to Fix:

The vehicle is raised and held on jack stands

The crankshaft damper and timing belt is removed

The crankshaft seal is removed and a new one installed

The timing belt and cover along with crankshaft damper is reinstalled

The engine accessory belts are installed and the vehicle is lowered off of the jack stands

Our Proposal:

One of the most essential parts of your car, crankshaft seals are typically made from a durable material, such as a synthetic rubber or silicone, designed to handle the extreme pressure and temperatures as well as the caustic chemicals in your engine oil. Because they are exposed to such abuse, main seals are subject to a lot of wear and tear. And whether you are talking a front or rear main seal, replacement is the only cure when one malfunctions.

The good news is that the seals are relatively inexpensive parts. The bad news is that neither is easy to change.

Front seal: The front seal is positioned behind the main pulley that drives all the belts, which is, of course, always rotating. The main pulley throws any leaking oil out in a big circle. It can get thrown up on the alternator, steering pump, belts, in short anything attached to the front of the engine and cause a real mess and eventually some serious damage. Consequently, it has to be removed along with many of the components attached to the front of the block to change the front main seal.

Rear seal: The rear crankshaft seal is positioned along with the transmission; therefore, the process of changing it requires the removal of transmission, as well as the clutch and flywheel assembly. This is a very involved job.

Common symptoms indicating you may need to change the Front Crankshaft Seal:

Oil leaking from the front crank pulley.

Oil dripping from the bottom of the clutch housing, where the block and transmission meet.

Clutch slip caused by oil spraying on the clutch.


Importance of this service:

Letting either crankshaft seal continue to leak can be harmful to your vehicle’s continued operation. Besides the maladies caused by driving around with little to no oil flowing in the engine, the defective seal will be spread oil through the engine bay and undercarriage of your car as you drive, a mess that is difficult to clean up and can be a fire hazard. Replacing is better addressed sooner than later.