Frank Castle's blog : A Guide to MOT and Exhaust Emissions Tests: The Basics, Importance, and Common Defects.
A guide to MOT and exhaust emissions tests: The basics, importance, and common defects.
For cars over three years of age, the MOT test becomes a legal requirement. This is a general statement that every car owner in the UK is familiar with. The test is designed to check a vehicle’s safety and emissions standards, and this too is general knowledge for drivers. However, what most car owners remain unaware of is the importance of the exhaust emissions test in the MOT. With only a few exceptions, the exhaust emissions tests are a necessity for every car in the UK. This is to check that your car’s emissions are within the stipulated levels followed by both national and European standards. Find out more in this guide about the importance of exhaust level checks in the MOT test in Northampton.
The basics of exhaust emissions tests.
The exhaust emissions test is to measure the gases that a car’s exhaust produces. During the test, the gas emissions are compared to the guidelines using specialist equipment. The following are some steps that every MOT tester will follow during an emissions test:
- As the test begins, a probe or an exhaust gas analyser is placed in the tailpipe of your vehicle. This equipment is usually a nationally approved one and is calibrated using a CRS (Certified Reference Standard).
- The tester will turn on the vehicle and measure the levels of four core exhaust gases. These include oxygen (O2), carbon monoxide (CO), carbon dioxide (CO2), and hydrocarbons (HC).
- Besides these gases, the tester will measure the air-to-fuel ratio in the gas. This is also known as a metric, “lambda”.
- Finally, the tester checks for the overall value of the efficiency of the engine.
Some vehicles are part of the exemptions list in an MOT. The following are some exceptions:
- Petrol vehicles used before August 1975 or diesel vehicles used before January 1980. These vehicles are not checked using the meter method but by looking at what comes out of the exhaust.
- Vehicles having 2-stroke engines.
- Vehicles that have less than four wheels.
- Electric and hybrid vehicles.
Common damages in MOT emissions tests.
During the test, the exhaust system and the emissions that are coming from the system form an important part. It also includes checking for the noise levels.
Testing for noise.
During the tests for noise, the following checks are included:
- Exhaust silencers
- Noise-deadening material fitted as original equipment under the bonnet.
- The tester checks exhaust noise by revving the engine to around 2500 rpm.
For noise testing, the following are some common defects that can fail your vehicle:
- The level of noise from the exhaust being excessively beyond the limit: Major defect.
- Insecure fitting of any component of the noise suppression system: Major defect.
- There are chances of a component becoming detached: Dangerous defect.
Testing for exhaust and emissions.
During the test for the exhaust system, the tester checks components that are visible and identifiable. This includes checking the exhaust gas recirculation valves, catalytic converters, and the oxygen sensors. The following are some defects that can cause your vehicle to fail the MOT:
- If any part of the exhaust system is missing or suffers from extreme damage.
- If the exhaust system is insecure due to missing or damaged mountings.
- If any component has a major lea in the system.
- If the system is emitting more noise than normal.
For testing of the emissions, here are some common defects that can result in failure:
- Excessive smoking found during visual checks: Major defect.
- Missing parts or defective parts or modification of the emissions control equipment: Major defect.
- Emissions levels that fail to remain within the specified limits of the manufacturer: Major defects.
- Emissions levels beyond the default limits: Major defects.
- An excess of Lambda coefficient from the default limits or the manufacturer’s limits: Major defects.
- If the emissions test remains incomplete: Major defects.
- The exhaust system emits blue or black smoke during a period of 5 seconds of idling: Major defects.
- Black or dense blue smoke from the exhaust system when the vehicle accelerates: Major defects.
- Fluid is leaking excessively and might harm the environment or cause safety risks for other drivers: Major defect.
- There is leakage of fluid that might lead to road safety risk: Dangerous defect.
The importance of exhaust emissions tests.
A commonly asked question from car owners is regarding the importance of exhaust emissions tests. Let’s look at the major reasons behind the importance of this test:
- The pollutants that a car emits lead to various health problems. The most common of them are allergies, skin irritation, heart diseases, respiratory problems, and even lung cancer.
- There could be chances of carbon monoxide poisoning in the cabin if the exhaust system is blocked. Headaches, respiratory problems, and heart diseases can result from breathing in CO.
- Air pollution due to car exhaust emissions causes severe harm to the environment, and some gases even contribute to global warming.
Overall, the exhaust emissions standards are important for every car owner to follow. If your vehicle’s MOT is due soon, regular servicing and checks of the exhaust system might help you to avoid failure due to common damage. Invest in timely exhaust repair in Northampton for an efficient car and a step ahead in environmentally friendly driving.
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