But there is also a situation when the car emission part will definitely need to be replaced. And this is known as oxygen sensor contamination. This is when the emission component is destroyed by a problem with the vehicle.
O2 sensor contamination
If I pull out an oxygen sensor that is contaminated I will usually check into it with my bore scope and insert it into the hole where the sensor is mounted. This is a quick way to check for fluid other than water which is naturally occurring in the exhaust system.
But since most people do not have a bore scope you may have to disassemble the exhaust before the oxygen sensor that was having a problem and shine a flashlight in there to see if there is any oil or coolant present. If you find any of these fluids you have a bigger problem than a bad oxygen sensor.
What else can cause O2 sensor problems? There is one other thing that can cause a contaminated exhaust stream sensor. RTV which is the automotive term for silicone caulk and stands for room temperature vulcanizing is not good for the health of the sensor. This type of contamination is most common after a previous repair to solve some type of external leak.
Inspecting for 02 contamination
The color and smell of the part may also indicate the problem or at least send you in the right direction. If the tip of the probe has a sweet smell this is a strong sign that it has been contaminated by engine coolant. If it smells burnt or has a black or brownish sludge like coding then this is a sign that oil has been entering the exhaust system.
As mentioned above if it is a silicone contamination this will usually leave white deposits on the exhaust sensor tip. Whenever you run into a contaminated sensor you really should replace it. I have never been successful at cleaning and reinstalling the component.
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