Rear Main Seal Leak Symptoms – How To Notice Them?October 7, 2021
Have you noticed some drops underneath your car where the transmission is located? The fluid does not resemble transmission fluid, it’s all black and it looks like motor oil. How come? This oil leak is because your rear main seal has failed and is leaking oil from the rear side of your engine. But you shouldn’t panic, everything is under control, in this article we are going to cover everything you need to know when it comes to the rear main seal leak symptoms and more.
Finding the root of your problem is the key in this situation. Every leak comes from somewhere on the engine or the other components. But you need to be able to pinpoint the exact issue that is causing this problem to appear. Knowing these skills, you will be able to tell what is the problem and tell the mechanic, hey my rear main seal is leaking, can you take a look?
Being able to do so, will save you thousands of dollars on possible repairs because most mechanics look to shave you off and find problems where there are any and change a ton of components on your vehicle. In the end, you will end up with an empty pocket. That’s why don’t be that guy. And we are going to help you out not to be that guy. But how?
In this article, we are going to learn what is a rear main seal, then we will discuss all the rear main seal leak symptoms and then we will find out how to diagnose the issue, then the costs that will be involved in fixing this problem. And lastly how this work is performed. So, without further ado, let’s dive into the article.
What Is A Rear Main Seal?
The rear main seal or rear crankshaft seal as it is known is a seal that is installed on internal combustion engines. There are usually two seals, a front main seal that covers the front of the crankshaft and a rear main seal that we discuss in our article that is located at the back of the vehicle where the transmission connects with the engine.
The rear main seal is a rubber gasket whose main job is to keep all the oil inside of the engine and not to let the oil escape while keeping the rotational momentum of the crankshaft.
As the years go by, these seals are getting old, as they age, they become brittle and plastic. When they become like hard plastic, they are not maintaining the level of performance as they did before when the gaskets were new.
When these seals fail, they start to develop rear main seal leak symptoms that we are going to cover later. The most important thing is that this problem is not quite serious and cannot cause damage to your engine in most cases. But there are still cases where the repercussions of not getting this rear main seal on time after spotting the rear main seal leak symptoms become quite an expensive repair. And you don’t want that.
That’s why you need to learn all of the rear main seal leak symptoms and then the prices that are involved in solving this problem as quickly as possible. Also monitoring the level of oil is key in order to avoid some permanent engine damage that we are going to discuss later in this article. But first, let’s cover the symptoms that are involved in this problem.
Rear Main Seal Leak Symptoms
Similar to other issues that we have in our cars when the rear main seal starts to leak there are rear main seal leak symptoms that develop based on this condition. Luckily, they are not many, and is fairly easy to diagnose this issue. In this chapter, we are going to cover all of these symptoms and then we will guide you into the diagnosing process. So, without further ado, let’s dive into the symptoms and find out how the rear main seal leak looks like.
Oil Leaks On The Ground
The first and most obvious symptom are the visible leaks on the ground. Just take a note that it doesn’t necessarily mean that your car has a rear main seal leak if there are leaks on the ground.
The first thing you need to do is to inspect the leaks. Try to feel the fluid and how does it fee with your hand. If the fluid is green in color or blue, it’s not an oil leak. This fluid is probably the coolant and, in this case, you need to check your coolant level and see if there are any leaks on the hoses.
If the fluid is red and oily, it means that your transmission is leaking transmission fluid or ATF as it is known. In this case, you need to inspect the transmission fluid level and see if there is a lack of transmission fluid. If there is a lack of fluid then this is your culprit. The transmission oil pan is probably leaking and the gasket of the transmission pan needs replacing.
If you notice that the leaks on the ground are dark black or brown, then you know that this is an oil leak coming from your engine. The first thing you need to do in this situation is to check the level of oil and top it off if there is a lack of oil.
The second thing you need to do is to diagnose the rear main seal leak, and how you can do that work we are going to discuss later in the article, but first let’s finish all the rear main seal leak symptoms.
Low Oil Level – Rear Main Seal Leak Symptoms
Low oil level is the second clear symptom that you will notice if your rear main seal has a leak. It is important to note that rear main seals do not leak as an oil pan gasket or leak from the oil pan does.
If the rear main seal is completely off, it will stop holding the oil and you will start to lose big quantities of oil that could even put your engine at risk.
Risking of scrapping the engine is not an option and most people replace their engines because they never check the oil level. Imagine that your rear main seal leaks and you continue driving like this. All of the oil will drain from the engine and the engine will suffer permanent damage that will cause it to seize eventually and your car will stop.
This is not an option. That’s why you need to observe your oil level regularly and make sure that you are not left without oil in your engine.
If you notice that you are losing oil, buy a quart from the gas station and top it off until you come home. By topping it off, you will know that you have oil and your engine will not seize and destroy itself.
When you notice this low oil level situation in your engine the first thing you need to do is to top off the oil as we mentioned. The second thing you need to do is to diagnose the issue. But how can I diagnose a rear main seal leak? We are going to cover that later in this article after we finish the rear main seal leak symptoms.
Splashes Of Oil On The Undercarriage
Another symptom that you could only notice are the splashes of oil on the undercarriage or in the engine bay if the car is front-wheel drive.
This is the case because as the crankshaft rotates, the oil splashes on the surrounding environment and makes all the components wet in oil.
This cannot be always seen but if you take your car to a mechanics shop, the mechanic is going to notice these leaks right away.
The important thing when you have leaks of this magnitude as we said is to check the oil level and top off the oil in order to avoid oil starvation in your engine and your engine to avoid some permanent damage by this annoying leak.
But how to diagnose this problem? Well, we have covered some of the diagnosing in this chapter but we are going to fully cover how to diagnose a rear main seal leak in the next chapter where we will dive into detail when it comes to finding out the root of this problem.
How To Diagnose A Rear Main Seal Leak?
In order to diagnose a rear main seal, leak you need to have access from beneath the vehicle. This means that the vehicle has to be mounted on a lift and then inspected.
Diagnosing these leaks is fairly simple. If the leak comes from the end of the crankshaft where the flywheel comes in contact with the transmission. Then this is a rear main seal leak.
The rear main seal has to be replaced with a new one and this is a lot of work, to be honest for a simple thing like a rubber seal. This work also tends to cost quite a lot, to be honest, and that we are going to discuss later in this article where we will cover all of the costs when it comes to solving this problem permanently.
How Much Does It Cost To Fix This Problem?
We have covered all of the rear main seal leak symptoms and how to diagnose this issue. Now let’s see how much does it cost to fix this problem permanently from your car. Just to note that fixing this problem does not come cheap and replacing this seal tends to cost quite a lot of money to be honest.
This is the case because the whole transmission has to be removed from the vehicle and then the flywheel also has to be removed in order to access this seal. So, what are the costs for this work?
The seal is cheap, it costs $5 to $15 and you can find it at any parts store. The expensive thing is the labor which is costly. The average hourly cost is somewhere between $50 to $100. And considering how many hours are involved in this job it can add up pretty quickly.
Either way, you cannot expect to perform this job cheaper than $500 and that is if you are lucky. In most situations, you will pay somewhere between $800 to $1200 to get this problem sorted. Or if you have a friend that has a lift, you can perform this work at their house for a fraction of the price. And how you can perform this work we are going to explain in the next chapter in great detail.
What Is Involved In Fixing This Problem? – Rear Main Seal Leak Symptoms
As we said, fixing this problem is quite a challenge. This is the case because the car has to be jacked in the air with a lift or jack stands.
Then the driveshaft has to come off from the car, this will involve removing the bolts that are holding the U-Joints, and then you will be able to remove the driveshaft.
After removing the driveshaft, you will have to remove the flexplate that is mounted on the engine. And after removing the flexplate you will be able to come to the rear main seal and remove the seal.
Removing the seal can also be a challenge and you will have to put a hole in it and wiggle it out from its place. After removing the old rear main seal, you have to install the new seal and then repeat the process in reverse order.
This work is not DIY friendly because it involves a lot of equipment needed to secure the car and the transmission. It is also very likely that you will need a pair of extra hands to help you out with this work. So, if you consider yourself fit for the challenge you can try. But the best thing is to leave this work at the mechanics and let them deal with it. You may pay more, but you will avoid doing this messy work.
Can I Continue Driving Like This?
Continuing to drive like this is a risk. You can do it but you risk leaving your engine dry from oil. If your engine runs with an oil level that is below the bare minimum. The engine would simply start to friction and the components will wear down prematurely.
The bearings will suffer the most. Then the O-rings on the pistons. The engine will start to overheat and eventually, it will seize when the damage is going to become too large for the engine to continue working.
The best thing to do when you notice that you are losing oil is to top off the oil with new oil. This will make sure that your engine will be safe until you reach a repair shop where this problem could be tackled.
Conclusion – Rear Main Seal Leak Symptoms
In this article, we have covered a lot when it comes to the rear main seal problem. We learned what is a rear main seal and what is its role. Then we have covered all of the rear main seal leak symptoms and then we have covered how to diagnose this problem quickly and effectively.
Then we have covered the costs when it comes to fixing this problem. Just to note again that isn’t cheap since a lot of components have to be removed from the car in order to gain access to the seal and replace it with a new one.
Lastly, we gave you our honest opinion if you should drive your car like this and the answer is no, this is the case because the seal when it fails tends to leak quite a lot and this can be dangerous if you drive your car without proper working seal. This will result in oil starvation and engine damage. So, don’t do it. Replace your seal as soon as possible and you will benefit in the long run.
If you want to read more about engine problems you can check out our articles on burnt valve symptoms, engine rebuild cost and front main seal repair cost.