Using BlueDevil to stop your Rear Main Seal Leak

Rear Main SealRear Main Seal leaks can be annoying, expensive, hard to deal with and downright frustrating.  Today, we’re trying to seal a rear main seal leak in our project car.  We are working on a 1977 Pontiac Trans Am.  These iconic cars were available starting in 1967, but the most recognizable models were built in the late 1970’s and were made famous due to the huge number of them sold, and the movie “Smokey and the Bandit” that this car was featured in.  The Trans Am was famous in its time because it was one of the last few true muscle cars made during an era of high gas prices, gas shortages and new emissions laws that started changing the way automobile manufacturers made cars, and specifically which engines they decided to put in them.

rear main sealIn 1977, the biggest engine you could get in a Trans Am was the Pontiac 400.  The car we are working on today has an engine borrowed from a 1976 Trans Am and is the biggest engine Pontiac used in their muscle cars.  The Pontiac 455 is a massive 7.5L engine that is known for making tons of torque.  This motor has been rebuilt with forged high compression pistons and rods, had the rotating assembly balanced, head work done and has been outfitted with many other performance goodies.  This motor also has a roller cam conversion to reduce the regular maintenance that needs to be done adjusting valves, and so we could take advantage of a very aggressive roller cam increasing valve lift and duration with plenty of overlap.  All that means lots of power, and a steep price tag!

After spending all that money on a motor for our project car, you can be sure we were surprised when we started seeing puddles of oil underneath the car.  During any engine rebuild, it is important to replace all of the seals, gaskets or other components to make sure when you start it for the first time you don’t have any leaks.  In our case, our motor got a fresh set of gaskets, seals, and freeze plugs so the leak we found came as a shock.

rear main sealerOur project Pontiac has gone a lot like one of your projects may have.  It got started quickly and with a lot of excitement but after the budget ran low and time ran short, the project started to slow down.  What started as a 1 year project has turned into a 5 year project and is still slowing making progress.  The motor for this car was installed 3 years ago and in that time only has had about 1500 miles put on it.  It may seem like a good thing that the car has been driven so little, but in this case it cost us a rear main seal.  Driving your car helps keep oil moving through your engine which will condition the seals and keep them from drying out.  Also, sitting for a long time can cause shaft seals to lose their shape.  If the shaft, in this case, your crankshaft, is just slightly out of alignment with the seal due to manufacturing tolerances or simple wear, it can slowly deform the rear main seal.  If your car is driven regularly the seal will stay soft and round sealing oil from leaking around the shaft.  If the shaft sits for a long time it can deform the rear main seal into an oval where the opening is no longer round and oil can leak out while the engine is running.

rear main seal leakIn our case, the very few miles we’ve put on our project car has caused the rear main seal to deform in this way.  We identified the leak by a small puddle under the car right where the engine bolts to the transmission.  We confirmed that we did have a rear main seal leak by noticing oil drips from the bottom of the bell housing and checking for a higher leak.  The back of the engine was dry all the way down to the bell housing which means our rear main seal is the source of the oil leak.

To replace the rear main seal leak in our Trans Am, we would have to remove the engine and transmission and after spending a lot of time and effort painting the engine bay we didn’t want to risk scratching or denting it.  In this case, our best bet was to add BlueDevil Rear Main Sealer to the engine oil and see if it worked!  After 2 short drives of about 5 miles, we already noticed a reduction in the amount of oil that was dripping on the ground afterward.  After 2 weeks of short drives, our leak is nearly gone and we’re expecting a full recovery!

BlueDevil Rear Main Sealer

If you are struggling through a rear main seal leak try BlueDevil Real Main Sealer today!  You can get more information about BlueDevil Rear Main Sealer here: Rear Main Sealer

You can purchase BlueDevil Rear Main Sealer at these local auto parts stores:

  • 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:

Trans_Am.jpg – By Stuurm – Licensed By Creative Commons Via Wikimedia – Original Link

12 responses to “Using BlueDevil to stop your Rear Main Seal Leak

  1. So, after you used this Blue Devil rear main seal sealer .. How well has it solved the problem … Now that some time & miles have been driven. Please do let me know! My ’99 Cadillac has the same problem too. Yes, it’s a front wheel drive & the oil dripping around the pan & floor isn’t …a Trans fluid!

    1. Lowell-

      The BlueDevil Rear Main Sealer brings the seal back to its normal size, flexibility, and condition thus giving it the life of a new seal. After adding the BlueDevil Rear Main Sealer you should notice results once you have driven about 100 miles.

      Thank You!


  2. Please respond to my question on the ‘Drain & Flushing out the cooling system, removing the Stat. Before using the Head sealant on my 1999 Cadillac. The instructions says; no need to drain the water & sealant once used. How then .. Do I reinstall the Stat & add antifreeze … Without draining?

    1. Lowell,

      Thanks for your question about your Cadillac and sorry for the confusion on the directions. The instructions stating there is no need to drain the water and sealant once used is there just to let you know that having BlueDevil Head Gasket Sealer in your coolant long term will not damage anything so you do not need to flush the system or fully drain it after use. You can drain the system just enough to allow you to reinstall the thermostat and add antifreeze to the water until it’s at the proper concentration.

      If you are using prediluted 50/50 antifreeze you will have to drain the system completely to ensure the proper antifreeze to water ratio.

    1. Faizal-

      Yes, the BlueDevil Rear Main Sealer is compatible and safe to use with your Mercedes B200. You should expect to see results after about 100-200 miles of driving.

      Thank you!


    1. Miguel-

      BlueDevil can stay in the oil for the life of the oil. You do not need to change the oil out immediately after results are achieved. Feel free to contact our technical support line at 888-863-0426 with any other questions.

      Thank you!


  3. Do you have to replace the Blue Devil sealer every time you change oil?
    My Pontiac 455 HO just started seeping a very small amount of oil. I hope that by catching it early the sealer will stop the small amount of seepage. I will try it before going and spending $ 750 with no guarantee new seals will stop the leak.

    1. Fred-

      You should only need to use BlueDevil once. It is not the kind of product that would need to be added with every oil change. Once the product seals, it would be a permanent seal. Feel free to contact our technical support line at 888-863-0426 with any other questions.

      Thank you!


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