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Finding oil buildup in your air intake hose is a real cause for alarm. Not only can this affect the performance of your vehicle, but it can also pose a safety hazard. This article will delve into the causes of oil in the intake hose and provide solutions accordingly.

Common Causes

Poor crankcase ventilation: The role of the crankcase ventilation system is to exhaust exhaust gases and oil vapors from the crankcase and prevent them from entering the air intake system. If this system is clogged or fails, oil vapors can accumulate in the intake hose.
Turbocharger Failure: Turbochargers use oil for lubrication, and if the seals are damaged, oil can leak into the intake system.
Excessive Oil Pressure: If internal engine parts are badly worn. This can lead to excessive oil pressure, which can cause oil to leak from the seals.
Damaged intake pipe seals: A damaged seal between the intake pipe and the engine can also cause oil to leak.

air intake hose
air intake hose


Reduced Intake Efficiency: Oil contamination can obstruct airflow and reduce intake efficiency, resulting in reduced engine power and increased fuel consumption.
Pollution of sensors: Oil contamination will pollute the intake air flow sensor, oxygen sensor, etc.. Leading to abnormalities in their work and affecting the engine’s fuel injection and air-fuel ratio control.
Causing safety hazards: Serious accumulation of oil contamination may cause intake pipe combustion, resulting in safety accidents.
Intake pipe blockage: Long-term oil accumulation may lead to intake pipe blockage, which in turn affects the normal operation of the car.

Diagnostic Methods

Check the crankcase ventilation system: check whether the ventilation pipe is blocked and whether the valve is working properly.
Check the turbocharger: check the turbocharger for oil leakage disassemble and check if necessary.
Measure oil pressure: Use an oil pressure gauge to measure the engine’s oil pressure and determine if it is too high.
Check the intake pipe seals: check whether the seals between the intake pipe and the engine are damaged, and replace them if necessary.


Clean the air intake hose: Remove the air intake hose and use gasoline or special cleaner to clean the internal oil.
Repair the crankcase ventilation system: Replace the clogged ventilation line and repair the damaged valve.
Replace the turbocharger: If the turbocharger is badly damaged, it needs to be replaced.
Reduce oil pressure: fix faults that cause high oil pressure, for example by replacing worn parts.
Replace intake pipe seals: Replace damaged seals and ensure that the intake pipe seals well.


To sum up, The presence of oil contamination in the air intake hose is not a trivial matter, and the cause should be identified and repaired on time so as not to affect the performance and safety of the vehicle. Hope that the information provided in this article can help you solve the problem.

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