Therefore, additional time should be taken to assess the cause of this expedited oil usage. If a weekly inspection of our vehicle’s engine reveals unanticipated oil loss, or if you suddenly find yourself adding more oil to your engine than normal, a worn rear main seal could be to blame. This rapid loss of oil will necessitate frequent top-offs, to avoid an engine’s oil from dropping to dangerously low levels. In severe cases, a compromised rear main seal can leak as much as a quart of oil in a week’s time. Rear main seal leaks are known for their tendency to leak an excessive amount of oil in short order. It is also possible for this pooling of oil to worsen with time. Therefore, the sudden appearance of an oil stain within the driveway is cause for concern and should be carefully studied to determine its point of origin. This, in turn, leads to the puddling of oil beneath a vehicle’s engine, leaving behind ample evidence of such issues. For this reason, a leaking rear main seal is often most evident in the minutes to hours after a vehicle has been parked for the day. Rear main seal leaks tend to worsen when an engine has warmed to its standard operating procedure. The following are the most common signs of a rear main seal leak. Being mindful of such symptoms will assist you in coming to an early diagnosis, thereby expediting the repair process. Signs of a Leaking Rear Main SealĪ rear main seal leak can be identified in a number of ways, some of which prove far more evident than others. As such, a noticeable leak is presented, which can range in severity by substantial margins. Without a properly functioning rear main seal, a vehicle’s engine oil is allowed to escape outside of its normal point of retention within the crankcase. In most cases, it is impossible to view an engine’s rear main seal, once it has been installed, and a vehicle has been returned to service. Seals of this type are typically driven into a recess within an engine’s rear cover and are generally concealed within the bell-housing of the transmission itself. This, in turn, gives birth to the rear main seal’s nickname as the rear crankshaft seal. In the simplest of terms, a rear main seal is a seal used to prevent oil loss from the rear of an engine, where the engine’s crankshaft mounts to the transmission, via a flywheel or flexplate. Will Thicker Oil Help a Rear Main Seal Leak?.Can a Rear Main Seal Be Replaced Without Removing the Transmission?.What Causes the Seal to Leak or Go Bad?.#3 – Oil Saturation of Vehicle Underbody.