How to Tell If you Have a Rear Main Seal Leak


rear main seal leakNo one likes a leaky car.  It makes a mess in your garage or driveway, it’s embarrassing at work, and it makes you feel like your otherwise great car is on its last legs.  Sometimes, a leaking car is better than an empty bank account and that may just be the two choices you have if you have a rear main seal leak.

A rear main seal leak is often an extremely costly repair due to the other components that have to be removed to get to the rear main seal on your engine.  The good news is, you might not have a rear main seal leak!

When an engine leaks oil it will always drip down the engine to the oil pan but it often ends up at the back of your oil pan due to the way air flows under your car.  This means if your engine is leaking oil anywhere it will end up at the back of your oil pan which is right where oil drips if you’ve got a leaking rear main seal.

Before you spend a bunch of money on replacing your rear main seal, make sure that really is the problem you have.  If your engine is completely lean everywhere but the back of your oil pan, the leak still could be from your oil pan gasket just from a place you can’t see if your transmission is still attached.

If your engine has signs of an oil leak elsewhere, you’ve got two choices.  Either fix the leaks so you don’t have other problems making diagnosis difficult or clean your engine really well, drive a mile or 2, and check for leaks again so you can see where they are originating from.

Another way to positively ID rear main seal leak would be to check inside your transmission bell housing and inspect the back of the flywheel or flexplate.  If your rear main seal is leaking this should have oil splatter on the engine side.  If the leak is from your valve cover gaskets or oil pan gasket there shouldn’t be any oil on the flywheel.  If your bellhousing doesn’t have an inspection cover you may need to use a borescope to peek in through a drain, the clutch fork opening, or a gap in the housing near the block.

If you find out you do in fact have a rear main seal leak but replacing the seal doesn’t make sense for you or your vehicle, consider using BlueDevil Rear Main Sealer to restore the rear main seal in your engine stopping the leak permanently, guaranteed!

You can pick up BlueDevil Rear Main Sealer at one of your local auto parts stores like:

  • AutoZone

  • Advance Auto Parts

  • CarQuest Auto Parts

  • NAPA Auto Parts

  • O’Reilly Auto Parts

  • Pep Boys

  • Canadian Tire

  • Walmart


2 responses to "How to Tell If you Have a Rear Main Seal Leak"


  1. Stefan on October 16, 2020 at 2:02 pm

    Hi, will Blue devil rear main sealer also cover up other leaking parts such as valve cover gaskets? Thanks

    • BlueDevil Pro on October 19, 2020 at 8:14 am


      BlueDevil Oil Stop Leak is more concentrated and is the universal application that will work for various leaks such as oil pan leaks, rear main leaks, valve cover gasket leaks, etc. Whereas the Rear Main Sealer is less concentrated and specifically formulated exclusively for leaking rear main seals. If you are not 100% sure where the vehicle is leaking or there seem to be multiple leaks then we recommend using BlueDevil Oil Stop Leak.

      Thank you!


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