How To Fix The Rear Main Engine Seal With Bar's Leak

Written by chris stevenson
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How To Fix The Rear Main Engine Seal With Bar's Leak
(under the hood image by Lucy Cherniak from

Engine rear main seals and front seals wear out with age, become brittle and shrink. As a result, these rubber or fibre material seals allow oil to bypass them to the exterior of the engine. Rear and front main seals can be very expensive to repair since in most cases the engine must be removed and the engine dismantled. Oil additives that recondition the seals, by softening and swelling the seal material, can be obtained from most auto parts stores. Bar's Leak can be a solution for stopping a rear main or front seal leak.

Skill level:

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Things you need

  • Floor jack
  • Jack stands (2)
  • Drain pan
  • Box-end wrench set
  • Oil filter
  • Engine oil
  • Shop rags
  • Bar's Leak

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  1. 1

    Check under your vehicle to confirm that you have a leak coming from the rear main seal. The leak will come from the rear of the engine block where it meets the bell housing. Take special note of the size of the puddle on the floor to make a comparison with this area after you have finished.

  2. 2

    Shift the vehicle in park or neutral with the emergency brake engaged. Raise the hood. Use a floor jack to lift the vehicle high enough to place two jack stands under the front part of the mainframe near each wheel. Slide under the vehicle and use the appropriate wrench to loosen the oil drain plug. Let the oil drain into a pan. Use the oil filter wrench to remove the oil filter, twisting it counterclockwise until it's removed. Place the oil filter in the pan and remove the pan from underneath the vehicle.

  3. 3

    Replace the oil drain plug and tighten it firmly with the wrench. Lubricate the gasket ring on the new oil filter with some excess oil and screw it into its mount by hand until it tightens snugly. Finish tightening the oil filter with the oil filter wrench but do not twist it too tightly--the gasket ring will crush.

  4. 4

    Use the floor jack to lift the vehicle and remove the two jack stands. Lower the vehicle to the ground. Refer to your owner's manual for the correct amount of oil that your engine requires. Put in one less quart required to leave room for the additive. Check the dipstick to make sure it shows one quart low. Add a full can of Bar's Leak to the engine. Start the engine and let it run for five minutes then turn it off. Recheck the oil and add more, if necessary, to bring the level up to the top dipstick line.

  5. 5

    Test-drive the vehicle for an hour and check for any obvious oil leaks not associated with the rear main seal leak. If everything looks fine, drive the vehicle for at least 250 miles or three days. Check the vehicle for the rear main leak after this period. It should have reduced considerably or stopped completely.

Tips and warnings

  • When you add the Bar's Leak, change the oil and filter at the same time. This will reduce the contaminants and let the chemicals in the product work more efficiently.
  • Add Bar's Leak every 6,000 miles for extra protection.

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