Rear Main Seal Leak Symptoms

Working out if your vehicle has a rear main seal leak can be tricky. Why? – Because the parts that are involved in a rear main seal leak are often unfamiliar to the average person.

Rear Main Seal Leak Symptoms

That’s because the rear main seal is located in an area that makes it very difficult to reach.

rear main seal leak symptomsAs a matter of fact, the obscure location of the main seal leak signifies that this component really isn’t meant to be replaced during the life of the car at all. 

If it was they’d have made it more accessible!

What is a Rear Main Seal?

A rear main seal is a seal that goes over the crankshaft at the rear portion of the engine.

The seal helps to prevent dirt, dust and other debris from getting into your engine. It also helps to hold the oil inside the oil pain.

Why is a Rear Main Seal Leak an Issue?

A rear main seal leak is dangerous because of the nature of the seal itself.

The rear main seal makes contact with the crankshaft as it spins around.

It’s also situated next to one of the primary bearings within the engine that has to be lubricated with oil on a constant basis.

Should the rear main seal break, a large amount of oil will leak out of your engine as it is running.

This can cause a number of issues, such as reduced lubrication that can eventually cause your engine to seize.

Signs of a Rear Main Seal Leak

Due to the importance of the rear main seal, it is extremely important to be aware of the signs that could indicate that this component is leaking. Some of the tell-tale signs that are indicative of a rear main seal leak include the following:

An oil leak – When the rear main seal is leaking, your vehicle is going to start leaking oil, and it’s going to start leaking it at a rapid rate. You’ll likely notice puddles of oil underneath your car, such as on your driveway or in a parking lot.

Frequent oil top-offs – If you find that you have to add oil to your vehicle more frequently, even though driving routines haven’t changed, this could be a sign of a rear main seal leak.

Oil light becomes illuminated – If your oil light keeps going on, especially just after you have added more oil or had an oil change, chances are that you are dealing with a rear main seal leak.

Rear Main Seal Leak Symptoms – Fix It

The quickest and cheapest way to fix a rear main seal leak is to simply by a specially formulated sealer and add it to your car.

rear main seal leak symptomsYou can do this every now and again as a preventative measure, or when you first experience one of the issues listed above to see if it fixes the problem.  It could save you a fortune in repairs if it does.

There are plenty of good options out to choose from.  We recommend Blue Devil Rear Main Sealer.  We’ve used it on several occassions to good effect.  It’s cheap and very easy to use – just follow the instructions on the bottle and you’ll be done in a few minutes.

You can read our review of how it works here.


Do you have any major signs or symptoms to add?  If so, let us know below.

Check out this handy guide from Instructables for further help on diagnosing a rear main seal leak.

Looking to develop your repair shop skills?  Why not get a home welder, one of the most versatile tools for any number of joining jobs.


Sharing is caring!

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.