How to Fix Your Rear Main Seal Leak

rear main seal leakA leaky rear main seal can be one of the most frustrating leaks on a vehicle.  Many small oil leaks can go unnoticed for long periods of time and cause very few problems in the day to day operation of your vehicle.  A rear main seal leak, on the other hand, can quickly cause a lot of problems.  First, your rear main seal is the lowest seal in your engine so even a small tear or deformation in the seal can cause a very high leak rate.  High oil leak rates can cause dangerously low oil levels in your vehicle very quickly leading to permanent engine damage.  The other problem with a rear main seal leak is that it is so low on your vehicle that dripping oil will be blown back onto your transmission, chassis, electrical wiring and other important components on the bottom of your vehicle while you drive.

Oil covering the underside of your vehicle may not seem like a bad thing at first, but it can cause lots of problems for your vehicle.  Oil covered components can start to attract road grime and dirt which can start to cause things to gum up and possibly malfunction.  Also, electrical wiring is safe from oil as the insulation used in automotive wiring is oil resistant, but the plugs, connectors and junctions can easily fill with oil and cause degradation of the plugs, plastic and connections.

For these reasons it’s important to make sure you fix your rear main seal leak to help keep your car safe.  In order to fix a rear main seal leak it helps to understand why the leak has started.

Causes of a rear main seal leak:

  • Lack of Use
  • Low Oil Level
  • Excessive Engine Wear
  • Normal Wear and Tear

The Rear Main Seal in your car is the seal at the back of the engine that surrounds the crankshaft and keeps the engine oil contained while your engine is running.  The first way this seal can get worn out is from a lack of use.  As your engine is running, oil is splashed onto your rear main seal and the oil helps keep the seal soft and clean due to the conditioners and detergents in your oil.  Without this regular oil bath, seals can quickly dry out and crack or lose their form.  Also, as an engine sits without running for long periods of time, the crankshaft can cause deformation in the seals on the bottom causing a leak when the engine starts and the crankshaft begins to spin again.

Low engine oil level or excessive engine wear also can lead to a rear main seal leak.  A low oil level will leave the crankshaft spinning on the seal without any lubrication that can lead to excessive wear and a leak.  Also, excessive engine wear can leave metal particles suspended in your oil which can quickly cut away at your rear main seal leading to a leak.

Lastly, high mileage and normal engine wear can lead to a rear main seal leak.  No matter how good of a job your oil does lubricating the rear main seal and even if all other conditions are perfect, your rear main seal will slowly wear down due to the contact with the spinning crankshaft.

In any of these cases, your rear main seal is most likely salvageable.  Whether it is from normal wear, a lack of use or other reasons, your rear main seal can be restored to its original size and sealing capability by using BlueDevil Rear Main Sealer.  BlueDevil Rear Main Seal is a chemical sealing agent that will be absorbed by your rear main seal.  This will cause your rear main seal to return to its original size and shape sealing your leak and protecting your engine and vehicle.

BlueDevil Rear Main Sealer

For more information about BlueDevil Rear Main Sealer, check out our product information page here: Rear Main Sealer.

You can find BlueDevil Products, like our Rear Main Sealer at any of our partnering local auto parts stores like:

  • AutoZone
  • Advance Auto Parts
  • Bennett Auto Supply
  • CarQuest Auto parts
  • NAPA Auto Parts
  • O’Reilly Auto Parts
  • Pep Boys
  • Fast Track
  • Bumper to Bumper Auto Parts Specialists
  • S&E Quick Lube Distributer
  • DYK Automotive


Pictures Provided By:

rear_main_seal_leak.jpg – by Christos Georghiou – Licesnsed By Thinkstock Photos – Original Link

15 responses to “How to Fix Your Rear Main Seal Leak

    1. Antonio-

      Yes, BlueDevil Rear Main Sealer will and has worked well in BMW’s; it is 100% compatible. Once the product is added you can expect to start seeing results after about 100 miles of driving.

      Thank you!


  1. I gotta say I was skeptical at first. I have a 2005 Scion xB with 170,000 miles. It developed a rear main seal leak about 8 months ago. I would just add oil as I needed.

    Then I came across your Rear Main Seal repair product. Within 3 days the leak has disappeared. I keep checking after every drive to see if any oil is show up under my car. Not a single drop.

    This $13 miracle in a bottle saved me the cost of having my transmission dropped to replace the seal. Not sure how much that would be. Let’s just say it would be more than $13.

    I would recommend your product line to anyone. Thanks again!

  2. Autobody shop recommended that i replace my rear main seal. They just replaced a valve due to a small leak. There is no current leak but was told that it looks as if it will be leaking soon. Can i use this product before a leak occurs instead of replacing the main seal for a whopping $900?

    1. Brandee-

      Thank you for you interest in the product. Yes, you can use the BlueDevil Rear Main Sealer to revitalize and recondition the rubbers in the system, to swell or expand them back to their original state. You should expect results after about 100-200 miles of driving.

      Thank you!


    1. Earl-

      Yes, the BlueDevil Rear Main Sealer is compatible with your Chevy Tahoe. Feel free to contact our technical support line at 888-863-0426 with any other questions.

      Thank you!


  3. I have a couple of leaks on honda accord 1988, oil pan, rear main seal, valve cover, to seal all 3 how much do i use

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