Crankshaft Seals

Do you see oil traces between the engine and gearbox or behind the crankshaft pulley at the front of the engine? Crankshaft seals seal where the crankshaft exits the block, and we stock them as single seals and kits for both projects and regular repairs.

Front and rear seal

The crankshaft typically has a seal at each end: the front one sits behind the pulley or harmonic balancer, and the rear one seals against the flywheel. Both keep the oil inside the engine while the shaft rotates. A leaking rear seal can get oil on the clutch, so it can make sense to replace it while the gearbox is removed anyway. Seals for the camshaft can be found under camshaft seals, and the whole range is collected under oil seals.

How to choose a crankshaft seal

Choose by engine code and model year rather than just car model. The product names state e.g. 2JZ-GE/2JZ-GTE, SR20DE/DET or EJ20/EJ25. Also check:

• Position: front or rear seal.
• Design: single seal, kit or two-piece seal such as Cometic Ford 385 Series V8 Rear Main Seal - 2 Piece.
• Contents: a kit may contain more parts than the seal itself, so read the product description.

In this category you will find e.g. Fel-Pro, Cometic Gasket, Peterson Fluid Systems and OMIX, and there are also kits for e.g. Arctic Cat and Ski-Doo.

Installation and sealing surface

The shaft's sealing surface must be clean and free of grooves, as wear can make even a new seal leak. Press the seal in straight and lightly lubricate the lip with engine oil, unless the manufacturer specifies otherwise. The rear seal typically requires removing the gearbox and flywheel.

Frequently asked questions

How do I tell if it is the rear main seal that is leaking?

Oil at the bottom of the bellhousing or between the engine and gearbox can indicate it, but a leaking oil pan gasket or valve cover gasket can leave similar traces. Clean the area and find the highest point with fresh oil.

Should I choose a two-piece or a one-piece rear seal?

It depends on how the engine is designed. Some engines use a two-piece seal, others a one-piece ring, possibly in a housing. Choose the type that matches the engine code, and check the product description for the specific part number.

Should I replace the front seal during a timing belt change?

It is often sensible, because on many engines the seal sits behind the crankshaft sprocket, and a leak can contaminate a new belt. However, it depends on the engine's design, and some engines have a chain instead of a belt.