How to Repair a Leaking Crankshaft Seal

crankshaft sealOil leaks in your car are never fun.  Unless you’ve simply given up on your car and are just trying to get the last few miles out of it before it heads to the junkyard, oil leaks can be one of the most annoying problems to have with your car.  Oil leaks cause a wide variety of problems in your car.  First off, they make a mess.  Oil leaks will cover your engine, transmission and underside of your car in an oily film that is difficult to remove.  On metal parts of your car this oil film will attract road dust and dirt covering everything in a layer of black grime that can make your vehicle surprisingly difficult to work on.  On hoses and wires this oil film can accelerate deterioration and lead to vacuum leaks or electrical issues.

Not only is leaking oil messy, it can lead to oil burning on the hot area of your engine leading to harmful fumes and the danger of a possible fire.  Most importantly, leaking oil can lead to dangerously low oil levels in your engine which can lead to accelerated engine wear and possible catastrophic damage.  If the oil level in your engine gets too low the bearings for your crankshaft and camshafts won’t be properly lubricated, and in extreme cases your oil pump may become uncovered leading to low oil pressure and major problems.

crankshaft sealFor many years, the most accepted way of fixing oil leaks was to disassemble much of your engine and replace the gasket or seal that is leaking.  A gasket, usually made of paper, cork or rubber seals two stationary objects in your engine to keep oil where it should be.  This is the case in components like your valve covers, timing covers or the oil pan.  Seals on the other hand, are at the end of shafts and keep oil from seeping past the shaft as it spins.  Every shaft in your engine, like the crankshaft or camshafts are supported by bearings which need to be lubricated by pressurized oil to keep them from quickly wearing out.  This lubricating oil needs to be contained inside your motor where the shaft exits the engine or you will have an oil leak.  The seals in your engine accomplish this task over a wide range of temperatures, engine RPMs and other harsh conditions.

There are a lot of things that can cause the seals in your engine to start leaking.  First, simple wear and tear can cause the inside of the shaft seal to wear so much that it will start to allow oil past it.  Low oil levels can also accelerate this process.  The material that shaft seals are made from also can start to deform if your car isn’t regularly used and the shaft is allowed to sit stationary for multiple months.  Also, a lack of use can allow the seals to start to dry out as the rubber is kept pliable from the constant bath of oil they get during normal engine use.

In some cases, replacing the gasket or seal is relatively easy.  If you have an engine with overhead camshafts, the camshaft seals may be easily accessible at the top front of the engine.  Similarly valve cover seals usually don’t require the removal of many components to replace since they are on top of your engine.  Your crankshaft seal is unfortunately the most difficult seal to replace in your engine.  Your crankshaft will have a seal at the front and back of your engine and both require the removal of a significant amount of your engine to replace.  In some cases the motor will even need to be removed from the vehicle in order to replace the crankshaft seals.

Luckily, modern technology has allowed BlueDevil to develop a simple to use engine oil additive that can repair your crankshaft seals so that you never have to go through all the work of replacing them.  BlueDevil Rear Main Sealer is specifically designed to target your crankshaft seals for repair.  BlueDevil Rear Main Sealer is a non-particulate chemical sealer that will restore your crankshaft seals to their original size and pliability restoring their ability to seal against your crankshaft and stopping your oil leak.

BlueDevil Rear Main Sealer

For more information about BlueDevil Rear Main Sealer, visit our product information page here: Rear Main Sealer

You can purchase BlueDevil Rear Main Sealer at the link above or 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:

crankshaft.jpg – By Alex Kovach – Licensed By Creative Commons via Wikimedia – Original Link
crankshaft_bearings.jpg – By VX1NG – Licensed By Creative Commons Via Wikimedia – Original Link

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34 responses to “How to Repair a Leaking Crankshaft Seal

    1. Leland-

      Yes, the BlueDevil Oil Stop Leak would seal leaks coming from the Crankshaft Seal. Feel free to contact our technical support line at 888-863-0426 with any other questions.

      Thank you!


        1. William-

          Unfortunately, our product is not designed to work for the type of leak you are experiencing. BlueDevil Oil Stop Leak is specifically designed to work for leaking rubber seals/gaskets such as oil pan gaskets, rear main seals, valve cover gaskets, etc.

          Thank you!


  1. i have a crank shaft seal leak in a 2.4L engine (4 cyl) that has been leaking for about 7 months im considering purchasing but my question is, will it work? Will it work despite the age of the leak or age of the seal will it still repair the leak and for how long?

    1. Bas-

      We recommend adding one 8 ounce bottle of BlueDevil Oil Stop Leak into your engine oil. This product will work to seal leaking crankshaft seals. Once it has been added you can expect to start seeing results after about 100 miles of driving.

      Feel free to contact us with any questions.

      Thank you!


    1. R-

      Thank you for asking about your Chevy K1500. The BlueDevil Oil Stop leak would treat a leaking crankshaft seal. As long as you are not losing oil too quickly, you would be a good candidate for the product. Typically, you should expect to see results after around 100-200 miles of driving.

      Thank you!


  2. I have a 2008 Saturn vue 4 cylinder. Took it to Sears and they say i have a front seal gasket crank shaft leak. Very slow leak right now will your product work. Its pretty pricey but if it works its worth the price. Feed back would be greatly appreciated,

    1. Carmin-

      Thank you for asking about your Saturn Vue. Yes, the BlueDevil Oil Stop Leak would treat a leaking crankshaft seal. You can expect to see results after about 100-200 miles of driving. Feel free to contact our technical support line at 888-863-0426 with any other questions.

      Thank you!


  3. I have a 08 Kia Rio and I have oil leaking from my crankshaft seal and it leaks oil everywhere I park my car and would it stop my leak

  4. Greetings… I have added the rear main leak sealer yesterday, and am hopeful for promised results. So far, it appears to be effective. I do have a question, however: the label and instructions do not mention anything about how long the product should re,main in the oil, and whether it might be a good thing to change oil soon after the treatment has run its course. Do you recommend and oil/filter change soon following successful treatment? Please advise, and thanks you.

    1. Charles-

      You can leave the product in the oil for the life of the oil. It does not have to be changed out immediately after proper results are achieved. Feel free to contact our technical support line at 888-863-0426 with any other questions.

      Thank you!


  5. I have a slight oil leak at the main drive belt pulley on my 08 Cadi ESV. Will Blue Devil rear main leak sealer work for this leak. AND do I have to add a new bottle Blue Devil sealer with each subsequent oil change?

    1. Eugene-

      Thank you for asking about your Cadillac. Unfortunately, the BlueDevil Oil Stop Leak would not treat a leaking belt pulley. A hard part repair may be your best option.

      Thank you!


  6. Hi, i have a Ford Mondeo xr5 turbo (2.5L 5cyl turbo volvo engine) with what the mechanic has said is “Engine oil leaking (crank shaft oil seal)”. Will this product fix my issue, and if so, how long will the fix last? Thanks in advance.

    1. Vic-

      Yes, the BlueDevil Oil Stop Leak is safe and compatible to use with your Honda outboard motor for your leaking crankshaft seal. Feel free to contact our technical support line at 888-863-0426 with any other questions.

      Thank you!


  7. My mechanic says products like this can clog things in the long run and cause engine failure. He says to let it leak and add oil as needed. Your reply?

    1. Donald-

      The BlueDevil Oil Stop Leak does not harden or thicken in anyway, so it would not have any adverse affects on the engine or system itself. Overall, the product carries a success rate of a little over 90%. As long as you are not losing oil too quickly, you would be a great candidate for the product.

      Thank you!


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