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Oil coming out of exhaust requires quick repair. The problem occurs because of defects in the valve cover gasket, leakage through the defective pistons, or other issues, but it is always fixable.
Read on to find all the reasons behind dripping oil and learn how to fix them.
JUMP TO TOPIC
- 1 Why Does Oil Come Out of the Vehicle’s Exhaust? (7 Reasons)
- 1.1 Defects in the Valve Cover Gasket or Seals
- 1.2 Leakage Through the Blown Head Gasket
- 1.3 Damaged Piston Ring in Your Vehicle’s Engine
- 1.4 Broken Piston in Your Lawn Mower
- 1.5 A Clogged PCV Valve in Your Vehicle
- 1.6 Oil Leaking From the Damaged Valve Guides
- 1.7 Leakage From Broken Engine Block or Cylinder Head
- 2 How To Fix a Vehicle That Has Oil Coming Out of the Exhaust?
Why Does Oil Come Out of the Vehicle’s Exhaust? (7 Reasons)
The oil comes out of the vehicle’s exhaust because of damaged valve cover gaskets and head gaskets. It may also happen because of worn piston rings or pistons. Sometimes, the oil drips from the exhaust because of defects in valve stem guides, motor blocks, or cylinder heads.
Defects in the Valve Cover Gasket or Seals
The valve cover gasket stops the oil from escaping the engine. If a valve cover gasket gets damaged or fails to function correctly, the oil can come out in the car exhaust.
Similarly, the valve seals on the valve stem prevent oil from leaking past the stems into the combustion chamber. When they get damaged, the oil can quickly move past them.
Besides oil dripping from the exhaust, you might notice blue smoke, a burning oil smell, or engine misfires.
The gasket and seals may be damaged because of the following reasons:
- The components get brittle over time due to age and break or get damaged
- You might have aftermarket or poor-quality parts in your car
- Improper installation, over-tightening, or under-tightening of bolts
- Chemicals mixed with oil can damage the gasket and seals
Leakage Through the Blown Head Gasket
The head gasket is also a seal-like component that stops oil, coolant, and combustion gas leakages like white smoke. A damaged gasket causes the oil to leak, which may cause severe engine damage.
The gasket may blow due to the following reasons:
- The gasket cracks or warps when the engine overheats
- Detonation or premature ignition of the air-fuel mixture
- Corrosion due to coolant or oil contamination
- Physical damage due to road impacts
A blown head gasket can let the oil enter the combustion system. The oil joins the fuel in the combustion process, but because it does not completely burn, you will observe black oil in exhaust pipe.
Damaged Piston Ring in Your Vehicle’s Engine
Piston rings are circular parts of pistons that are vital in minimizing oil leakages and preventing oil from entering the combustion chamber. A damaged ring can cause the lubricant to pass into the combustion engine.
It leads to a decrease in the oil level in the piston, and the lubricant mixes with the engine oil. The constant leakage requires quick repair because it can cause fire hazards and engine damage.
The leading causes of a bad piston sealing ring are:
- Lean combustion mixture producing combustion gases (due to blocked foam air filters)
- Poor car maintenance leads to engines overheating, damaging the rings
- Damaged cylinder walls
- Dirt or debris in the ring
- Gradual wear and tear
- Using low-viscosity oil
Broken Piston in Your Lawn Mower
An engine piston in your car or lawn mower provides mechanical energy to the crankshaft. The crankshaft, in turn, is responsible for wheel rotation. It uses the pressure from burning fuel to power or move the wheel.
If an engine piston is damaged, it causes oil to leak through its gaps and holes, dripping through the lawn mower’s exhaust pipe. However, it can also cause the oil from the piston to move to the combustion engine.
The major causes of a defective piston are:
- Overheated engine
- Carbon deposits or debris
- Broken piston sealing rings
- Using oil with unsuitable viscosity
- Lack of lubrication or low oil pressure
- Leakage due to damaged cylinder walls
A Clogged PCV Valve in Your Vehicle
A positive crankcase ventilation (PCV) valve is a necessary part of the engine’s emission system that regulates oil vapors apart from gases in your vehicle. A clogged crankcase ventilation valve causes the vapors to build up inside the crankcase and into the exhaust stream.
The worn valves prevent the vapors from routing back into the engine, which causes car or mower exhaust problems. The valve can be clogged because of the following:
- Carbon deposits
- Engine oil vapors
- Oil sludge buildup
- Sludge and varnish
- Moisture condensation
- Contaminated air intake
- Faulty PCV system maintenance
Oil Leaking From the Damaged Valve Guides
The guides are cylindrical components that act as a barrier between the valves and the cylinder head that stop the oil from passing through. However, if a valve guide is damaged, it cannot hold the oil in its place, allowing excess oil to seep.
The oil leaks from the valve guide because of the following:
- Damaged valve seals
- Insufficient lubrication
- Overheated engine due to higher load
- A gap between guides and valve stem due to aging
- Contaminants such as dirt or debris caught up in the guides
Leakage From Broken Engine Block or Cylinder Head
Having a damaged or leaking engine, motor block, or cylinder head can also explain oil dripping into the exhaust manifold of a car or lawn mower. The block houses the cylinders, pistons, and crankshaft, while the cylinder head sits on top of the block and contains the valves, spark plugs, and combustion chamber.
These components contain passages through which oil circulates, so the lubricant leaks externally when damaged. The lubricant passages can get damaged due to the following:
- Improper assembly or installation
- Physical damage due to road impacts
- Freezing temperatures or overheating
- Clogged air filter causing detonation or pre-ignition
How To Fix a Vehicle That Has Oil Coming Out of the Exhaust?
You can replace the damaged valves to fix a vehicle with oil from the exhaust. You can also clean carbon deposits from piston rings or hire a mechanic to replace the pistons. Moreover, welding the cracks in the cylinder head or replacing it can stop oil leakage.
Replace the Obstructed Positive Crankcase Ventilation Valve
If the crankcase ventilation valve is damaged, you get help from a mechanic or replace it yourself.
- First, locate the valve, mainly on top of the motor block.
- Identify the valve. It is a small and cylindrical object, sometimes housed in metal or plastic housing.
- The third step is to disconnect the hose from the valve. To do this, you have to slide it off the valve gently and smoothly. If there are any retaining clips, release them.
- Then, you have to unscrew and pull out the valve. For this purpose, you may need pliers or a wrench.
- Inspect the valve properly for any sign of damage and carbon deposits.
- Install a new PCV valve in its place, which is appropriately aligned.
- Afterward, rejoin the hose by simply sliding or securing retaining clips.
- Start the engine to test the replacement. If there’s no leaking oil, then the replacement is a success.
Repair or Replace the Worn Valve Guides
If the valve guide is damaged, it should be replaced or repaired. There are two ways to fix a bad valve guide, i.e., knurling and bronze sleeve installation.
In knurling, you must hone the damaged valve guide to eliminate irregularities. Although cost-effective, the process should be performed by an experienced professional. The process requires a specialized tool to roll a knurling pattern into the inner surface of the guide.
The damaged guide is also reamed or honed during bronze steel installation. The sleeve is then installed by pressing or machining it into the required place. The sleeve should be appropriately aligned and fixed in place.
However, if the guides are damaged beyond repair, you can replace them by following the steps below:
- First, take off the cylinder head and clear the surrounding areas.
- Use a hydraulic press or specialized cutting tools to remove the valve guide. Avoid damaging the close regions.
- Then, special instruments must push the new guide into the hollow space.
- Sometimes, the valve seat area also needs machining.
- Once you reassemble the valve stem and valves on the valve seat, place the cylinder head on the motor block.
Replace the Faulty Valve Covering the Gasket
You can easily replace a valve cover gasket if you notice oil in the exhaust pipe. However, you can also use the help of a mechanic.
- First, find the valve cover, usually on the top of the engine. You can also search online to find its location.
- Remove the bolts that keep the valve cover in place using tools.
- Now clean the cover and engine to remove any debris.
- Place the gasket in the place of the old gasket. Align the valve cover and tighten the bolts. Make sure that it is in the right place.
- Attach all of the parts that were connected to the gasket before.
- Turn on the engine and look for any leaks. If oil doesn’t leak, then the operation is a success.
Repair or Replace the Piston and Piston Sealing Ring
A standard recommendation is to replace the piston sealing ring rather than repairing it. However, if there are carbon deposits in it, then you should use penetrating oil to remove them. You can also use soft brushes to clean the ring thoroughly.
Here’s what you can do if you’re wondering how to fix oil leaking into exhaust:
- To get to the piston, first remove the piston head.
- Now, you need to get the piston out. To do this, you must loosen the bolts or remove the pins.
- You must check for any damages when the worn rings are out.
- Clean the piston grooves and place the new sealing rings in place of the old ones.
- Put everything back in place and use compressional force to see for any leakages.
- The operation has proved successful if there are no leakages through the rings.
If the piston is damaged, take your car to a mechanic. If you have prior experience, follow the steps below:
- First, take off the cylinder head to get to the pistons.
- Remove the connecting rods and tap to get the piston out of the bore.
- Analyze the extent of the damage done to the piston.
- For minor scratches, you can use sandpaper.
- In case of severe damage, clean the cylinder bore and place the new piston in place of the previous one.
- Lastly, reassemble the other pieces.
Fix the Damaged Cylinder Head or Motor Block
If you have a damaged cylinder head, it is best to take it to a professional mechanic. You can only correctly analyze the extent of the damage if you have expertise in this area.
If the crack is enormous, replacement is the only thing left to do. For minor damages, you must first clean the area around the crack so there are no extra particles. Welding can fill the gap; if it’s big, put a metal sleeve into the cracked engine block.
If your car has a damaged motor block, first, you must inspect the damage amount. Clean the block precisely and use epoxy as a temporary solution for holes.
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