Oil Leaking from the Exhaust
Oil dripping from the exhaust pipe is an alarming sight. Where is it coming from and what damage does it cause? This strange phenomenon could indicate an internal engine problem that needs to be diagnosed.
Learn what causes oil to leak from the exhaust, how to identify the source of the problem, and whether it’s safe to continue driving because the oil could catch fire.
What does it mean when oil leaks from the exhaust pipe?
Oil can leak out of a vehicle’s exhaust pipe only if the oil has entered the engine’s exhaust stream at some point. However, this can be done in a variety of ways. Understanding these possibilities can help you diagnose and troubleshoot such issues if they arise.
Simply put, oil is introduced into the exhaust stream through the exhaust ports of one or more cylinders of the engine. This oil is forced downward into the engine’s exhaust manifold by the natural flow of exhaust gases. The oil is then sent rearward through the engine’s exhaust, catalytic converter, and muffler.
At the end of the vehicle’s exhaust stream, this oil appears as a black liquid dripping from the exhaust. However, this should not be confused with the sight of condensation or water dripping from a black soot-covered exhaust pipe.
Common Causes of Exhaust Oil Leaks
Oil can get into a vehicle’s exhaust system in a variety of ways. Some of these errors are more common than others, but it’s definitely worth understanding the intricacies of each. Below are some of the most common causes of oil leaking from a vehicle’s exhaust pipe.
1) Clogged PCV Valve
The engine’s crankcase ventilation valve is responsible for diverting a certain amount of burnt gases to each cylinder for further combustion. However, if this valve becomes clogged, excessive pressure can build up inside the engine’s crankcase, causing the seals to bypass.
As a result, oil can accumulate in the engine’s exhaust system. This can also lead to oil appearing in the intake manifold, throttle body, or intake pipes.
2) Blown Head Gasket
A blown head gasket can also cause oil to accidentally leak into the engine’s exhaust stream. When functioning properly, your engine’s cylinder head gasket separates the individual fluids in your vehicle from each other.
The head gasket prevents fluids from entering your engine’s combustion chambers. However, if the head gasket is defective, oil can leak directly into one or more cylinders.
3) Valve Guide Wear
Your engine’s valve guides prevent lubricating oil from passing over the valve stems in the cylinder head. But like any other component, your engine’s valve guides can wear out over time. This often causes oil to seep into the engine exhaust, producing bluish-gray smoke as a by-product. In severe cases, oil may even leak out of the engine exhaust.
4) Broken Piston Rings
Each cylinder in your engine has piston rings that move up and down with the movement of the piston in the cylinder itself. These rings perform the important function of preventing excessive combustion losses.
However, these piston rings also prevent oil from entering the combustion chamber. When one or more piston rings break, oil will usually leak quickly into the engine exhaust.
5) Block or Head Break
Structurally, an engine consists of a block and one or more cylinder heads. These major structural components must be kept in good working order to maximize engine performance.
However, often times, cracks develop in the cylinder head or engine block, causing engine oil to be lost into the combustion chamber. In this case, the oil is carried downwards until it eventually exits the vehicle’s exhaust.
6) Piston Damage
In rare cases, the head of one or more pistons in your engine may become damaged, allowing oil to enter the engine’s combustion chamber.
A certain amount of this oil is burned, and the remaining oil is discharged through the open exhaust valve into the engine’s exhaust manifold. If the damage is severe, some of this oil will be forced out of the vehicle’s exhaust.
Is it safe to continue driving?
In most cases, at the first sign of oil leaking from the exhaust system, you should drive your vehicle to the nearest service center and have it serviced. This is because issues like this are often indicative of a bigger problem, such as damage inside the engine.
Therefore, continuing to drive the vehicle in this condition may actually cause further damage, which may require more time and effort to take corrective measures. If too much engine oil is lost into the vehicle’s exhaust, it also poses a fire hazard.
Can oil in the exhaust ignite? Oil can actually ignite from a vehicle’s hot exhaust gases. This most commonly occurs when oil pools on or around the engine’s exhaust manifold, where the exhaust gases present are the hottest. In most cases, however, the oil will solder or smoke before an open flame actually occurs. The resulting smoke is usually bluish-gray in color.
Overheating engine oil also generally produces a burnt odor that is easily recognizable. This odor is usually noticeable even to people inside the vehicle, especially if the smoke is extracted through the vehicle’s fresh air ducts.
