4 Symptoms of a Rear Main Seal Leak
Some of the most difficult mechanical problems to identify and repair are oil leaks. A particularly dreaded rear main seal leak can send technicians on a pointless search and require laborious and time-consuming repairs.
Before you face this serious nuisance, arm yourself with knowledge. Learn about the most common symptoms of a rear main seal leak, how serious it is, and how much it will cost to replace it.
Signs of a Rear Main Seal Leak
A rear main seal leak can be identified in a variety of ways, some of which will prove to be much more obvious than others. Paying attention to such symptoms allows for early diagnosis and speeds up the repair process. Below are the most common signs of a rear main seal leak:
1) Oil Pooling in the Driveway
Rear main seal leaks tend to get worse as the engine warms up to normal operating conditions. For this reason, rear main seal leaks are often most noticeable within a few minutes to a few hours of parking the vehicle.
This can cause oil to pool under the vehicle’s engine, leaving ample evidence of such a problem. Therefore, the sudden appearance of oil stains in your driveway is a cause for concern and should be inspected carefully to determine its cause. This oil buildup may also worsen over time.
2) The Need for Frequent Refills
Rear main seal leaks are known for their tendency to lose excessive amounts of oil in a short period of time. In severe cases, a damaged rear main seal can leak up to a quart of oil in a week. This rapid loss of oil requires frequent refills to prevent the engine oil level from dropping to dangerously low levels.
If you discover unexpected oil loss during your weekly inspection of your car’s engine, or you suddenly notice that your engine is pumping more oil than normal, it may be due to worn rear main seals. Therefore, you should spend more time identifying the cause of this increased oil consumption.
3) Oil Saturation in the Vehicle Undercarriage
When the rear main seal is leaking, oil tends to accumulate inside the engine/transmission bellhousing, so it is not uncommon for the recoil to cause severe oil saturation in the undercarriage of the vehicle. When the vehicle is operating, the leaked oil is flushed backwards, covering the entire rear of the vehicle’s engine.
This is why regular inspections of your vehicle are especially important. In most cases, it’s enough to look under your car to find the telltale signs of a rear main seal failure. This will help you plan a repair before the leak gets worse.
4) The oil light comes on
If your car’s oil level light suddenly comes on while you’re driving, there are two things you should do. First, pull over to the nearest road as quickly as possible and turn off the engine. The next important task is to find where the engine oil has disappeared from. In these cases, the engine’s rear main seal is suspect.
Similarly, some vehicles will display a low oil lamp or a similar message.
What is a rear main seal? Rear Crankshaft Seal
Simply put, the rear main seal is the seal that prevents oil loss at the rear of the engine where the engine crankshaft attaches to the transmission via the flywheel or flexplate. This is why the rear main seal is called the rear crankshaft seal.
Noticeable leaks will occur, but the extent of them will vary greatly.
What causes a seal to leak or fail?
The most common cause of a rear main seal leak is simple wear. Although the seal is relatively tough, it doesn’t last forever. Rather, it’s entirely normal for engine seals to fail as the engine gets older and racks up the mileage. When this happens, they start to leak.
Rear main seal failures can become more frequent when the vehicle is stored for long periods of time. This type of seal typically relies on splash lubrication from the engine oil to prevent premature wear.
When the vehicle is idled for long periods of time, this splash lubrication stops, allowing the seal to dry out, harden, and potentially crack. As a result, leaks often become apparent shortly after the vehicle is put back into service. In rare cases, if your engine gets low on oil, the rear main seal may start to leak. While it’s unlikely to cause any problems if your engine runs out of oil by a quart for a short period of time, driving in this condition for an extended period of time can cause the seal to dry out and harden.
Therefore, you should check your vehicle’s oil level regularly to avoid future problems.
Is a Rear Main Seal Leak Serious?
A rear main seal leak is generally regarded as being quite serious in nature, due primarily to the fact that such leaks only tend to worsen with time. In severe cases, a rear main seal can leak to the point of creating difficulties when attempting to keep up with the resulting oil loss. Simply put, adding enough oil to maintain proper lube supply becomes troublesome.
However, this is still a far better scenario than what will likely occur should an engine become starved for oil, at the hands of a rear main seal leak. Any substantial loss of lubricating oil poses the risk of causing bearing damage, which can ultimately result in untimely engine failure.
At the very least, running an engine low in oil can, and will, cause premature internal wear. In any event, a rear main seal leak should be addressed at the first available opportunity.
Can a Rear Main Seal Be Replaced Without Removing the Transmission?
Conventional rear main seal replacement requires a vehicle’s transmission to be removed. This is necessary to gain access to the rear main seal itself, which is housed at the back of an engine, within the transmission’s bell housing.
Unfortunately, removing a vehicle’s transmission is no small feat, and is rather time consuming to complete.
Luckily, there are now several products on the market that claim to stop rear main seal leaks in their tracks. These products are designed to rehydrate an aging seal, thereby restoring its sealing power. Unfortunately, products of this nature are known to produce mixed results, leading some consumers to steer clear.
