The purpose of a crankshaft seal is to deflect oil back into the oil sump, or oil pan, to both maintain the proper oil level and prevent leaking onto the ground. Your engine has two crank seals; one seal is located at the front of the engine, behind the crankshaft harmonic balancer, and one is located at the back of the engine, behind the flywheel.

This article will focus on how to replace the front crankshaft seal. Although the steps provided below are similar for most engines, there are many different engine designs, so please refer to your factory service manual for detailed instructions on your particular vehicle.

Part 1 of 1: Replacing the front crankshaft seal

Materials Needed

Step 1: Prepare the vehicle. Jack the vehicle up high enough to obtain access to the harmonic balancer, which is located on the front of the motor and attached to the crankshaft. Secure it on jack stands.

Step 2: Remove the accessory drive belts. On many modern vehicles, there is an automatic, spring-loaded belt tensioner that can be rotated to loosen the belts.

You may need to use an open end wrench or ratchet handle depending on the design. Older vehicles, and even some newer ones, require you to loosen a mechanical tensioner.

  • Tip: Take a picture of the belt routing for future reference.

Step 3: Remove the harmonic balancer bolt. Remove the harmonic balancer bolt by using the strap wrench to hold the balancer still while loosening the bolt with a socket and ratchet handle or breaker bar. It will be very tight, so pull hard.

Step 4: Remove the harmonic balancer unit. Use the gear puller to remove the harmonic balancer unit. Place the hooks in an area that will not easily break, like the lip of the pulley section.

Some vehicles have threaded bolt holes in the balancer that can be used to attach a puller. Tighten the center bolt with a ratchet handle or breaker bar until the balancer breaks free.

  • Tip: Most harmonic balancers are kept from rotating on the crankshaft by using a woodruff key. Don’t lose the woodruff key, as you will need it for reassembly.

Step 5: Remove the old crankshaft seal. Using a seal puller, gently pry the old seal loose from the crankcase.

The objective is to try and hook onto the seal, between the seal and the crankshaft, and pry it loose. It may take several attempts at different positions to fully release the seal.

Step 6: Install the new crankshaft seal. Lubricate the new seal with fresh motor oil to prevent tearing of the seal and to make installation easier. Then, position the seal with the lip towards the engine block and press it on by hand.

Place the seal over the crankshaft with a seal driver tool and use a dead blow hammer to gently tap the seal into place.

  • Note: You can also use a large deep well socket or a pipe coupler as a seal driver if it has the same outside diameter as the seal itself.

Be sure that the new crankshaft seal looks properly installed.

Step 7: Install the new harmonic balancer. Align the woodruff key slot in the new balancer with the woodruff key and carefully slide the balancer onto the crankshaft, making sure the keyway remains in its proper position.

Install the center bolt and tighten until the required torque specification is obtained.

Step 8: Reinstall the belts. Rotate or loosen the belt tensioner to reinstall any accessory belts that were removed.

  • Note: Refer to any pictures you took or your factory service manual to determine the correct belt routing.

Step 9: Lower the vehicle. After supporting the vehicle with the floor jack, carefully remove the jack stands and lower the vehicle. Start the vehicle to ensure proper reassembly and operation.

Replacing a crankshaft seal is doable if you follow the correct steps. However, if you are not comfortable performing such a task yourself, a certified technician, like one from YourMechanic, will have the tools and skills required to complete the front crankshaft seal replacement for you.

This article originally appeared on YourMechanic.com as How to Replace a Crankshaft Seal and was authored by Richard Zeppetini.


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