Rear Main Seal Leak Symptoms & How To Fix?

Your vehicle’s engine has so many seals that keep engine oil in its proper section and also prevent it leaking out.

Rear main seal is one of the most difficult seals on the engine that it is very hard to replace.

This seal is the most crucial seal as it is so low on the engine a major amount of oil can quickly leak from the engine and the level get dangerously low before you add-on more oil into it.

We will first understand in details what is rear main seal leak? After that we will also discuss on rear main seal leak symptoms and how you can fix it.

After going through this article, you would probably be having sufficient knowledge about the rear main seal leak and how you can prevent it.

What Is Rear Main Seal Leak?

As we have understood earlier rear main seal is one of the most important seal. It is situated inside the rear of the engine where crankshaft connects with the transmission.

Sometimes if you will notice oil dripping from the back part of your vehicle, you should take immediate actions as it may cause many problems with your car.​

If your engine oil leak to significant amount, a low oil level in your engine may cause permanent engine damage. A low oil level will stop flowing through to the other parts of the engine such as bearings, cam shaft and valves.

Once these parts don’t get oil, they have to move without lubrication. Even in the normal speed of your vehicle, Lack of oil can cause permanent damage in very short period of time.​

The cause of rear main seal leak is not the fault of the seal itself every time. If you will fill oil level high up to full mark or the Positive Crankcase Ventilation system is not working correctly, it will start leaking.

Main job of PVC system to prevent pressure from building up inside the engine and if it is not working properly, that pressure will be the reason of rear main seal leak.​

Thus, it is very important to take care of your rear main seal from leaking. Read on following section to know the rear main seal leak symptoms so you would come to know when you should take immediate actions.​

Rear Main Seal Leak Symptoms

  • Oil Spots

​Oil spots are the most common symptoms of a rear main seal leaking. If you found any oil spots on the floor of your garage or on your driveway, it might be the sign of your rear main seal leak. Sometimes you would also find if your car is parked for long period of time.

  • Oil Level

​Along with the spots on the floor or in the garage, you would probably be noticed that the level of oil going down drastically even if you will make it full with the new oil.

  • Smoke

​If there is any smoke coming out from the engine because of the leaking oil from the rear main seal drip onto the exhausted engine and smoke coming out of the tailpipe would be the symptoms of the rear main seal leak.

  • Deposit of debris

​Usually, leaking oil acts as an adhesive on the bottom of the vehicle. Road debris and dirt sticks to the surfaces covered with oil. A deposit of debris and dirt at the junction of the transmission and engine can be the good indicator of a rear main seal oil leak.

Apart from the above symptoms, rear main seal leak has many other symptoms related to crankshaft seal. Over the time, if the crankshaft seal cracks, dries or break because of any reasons, it will start leaking oil.

If it has small leaks, it will accumulate on the undersides of the engine, while if it has larger leaks may product a drip of oil from the front side of the engine.​

How To Fix?

Fixing rear main seal leak is quite hard and tiring job but still if you will take following tips into the consideration, you would get rid out of this issue.

  • ​First step you should check for its seal. Sometimes oil seal becomes weak and oil start leaking. If this is the reason of your rear main seal leak, you just need to replace seal and it will cost you almost nothing.
  • There are many products in the market which temporarily swell the main seal and it doesn’t allow oil to leak. It will prevent from heavy flow of oil leak. There are other various “Stop-leak product” available in the market that can be your first step before getting it repaired.
  • Usually, rear main seal oil leaks through crankshaft. You should first remove the crankshaft along with a rope-seal application. And then again install the rope into the cavity in the block and the cap, and then roll it into place with a large dowel or pipe.
  • Sometimes, it is not important to replace the seal every time in order to stop a rear main seal leak. “A leak repair kit” will help you in most of the leak issues.
  • You may buy easily from any auto repair store. This kit uses a pushrod to drive a pointed steel spacer pin between the upper rear main seal and the block. Thus, you may tighten the old seal and may stop the oil leak.


Here detail article regarding what is rear main seal and about rear main seal leak symptoms. It is one kind of the leak which may lead to serious damage to your engine sometimes.

If you would overlook this rear main seal leak issue, it would completely destroy your engine and you will not have any other option except replacing it.​

So you should keep checking your rear main seal on a regular basis and if you will find any symptoms of leak, act promptly. You should get it repaired at the earliest or you should get it replaced with the new one.​

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