Engine Oil Seals
Two of the most important seals in an internal combustion engine are the front and rear engine oil seal. They are also known by other names, such as crankshaft seal and transmission seal. They keep the engine oil from leaking out of the crankcase and prevent contaminants from entering the engine. They are made from synthetic rubber and last many years, but will eventually need to be replaced as they perish and crack. Installing a new engine oil seal is a difficult task and often requires the removal of the engine or transmission.
In most vehicles, the transmission connects directly to the rear of the engine, which makes it difficult to see the rear engine oil seal. The front seal is more visible because the only thing in front of it is the crankshaft pulley. Both seals are located just inside the crankcase housing in recessed seats, in front of the bearings. They are large rubber rings with a diameter of several inches, and with a flat profile about half an inch thick. The seals are usually black or orange but other colors are also used. They are sold individually and as part of kits which contain all the main engine seals.
The primary function of an engine oil seal is to prevent the sump oil from leaking out of the crankcase bearings. This is important because oil is the lifeblood of every engine, and even a small decrease in the oil level can be damaging to the internal components. The secondary function of an engine oil seal is to prevent contaminants from entering the engine. Most vehicles have an engine bay that is open at the bottom, allowing water and dirt into the area where the seals are. Water causes corrosion of the metal parts inside the engine, and dirt causes abrasive wear. An engine oil seal helps avoid both of these problems which can cause expensive damage.
An indication that there may be a problem with an engine oil seal is a gradual decrease in the engine oil level, along with fresh oil stains on the engine and transmission, as well as on the ground under the vehicle. There may be other reasons for the leakage too, such as a cracked engine gasket or a loose sump plug. It is important to make sure that a faulty seal is the problem because replacing an engine oil seal takes a lot of time and effort. It is also important to get the right seal for the engine, as there are many different sizes available. Before purchasing a new seal, make sure it is compatible with the make and model of the vehicle.
Changing the rear engine oil seal in a vehicle with rear-wheel drive is usually done by removing the transmission, while one with front-wheel drive usually needs to have the engine removed instead. Before the old seal is removed, all the engine oil should be drained from the sump. Once the old seal has been removed, the recessed seat and new seal should be cleaned and lightly coated with oil. After the seal has been installed, new engine oil should be added to the sump. Before putting the engine and transmission back together, leave the vehicle sitting for a while and check for any leaks from the seal.
There are a couple of ways to avoid replacing a leaking engine oil seal in the short term. Using thicker oil may slow the leak but may also reduce engine performance, resulting in poorer fuel economy. There are also additives that can be added to the engine oil that swell the seal rubber and may stop smaller leaks. While it is possible to avoid changing the engine oil seal in the short term with these measures, it will continue to deteriorate and the leakage will worsen over time.
