Tech Tip: Air Filter Inspections

Tech Tip: Air Filter Inspections

Does your lube service technician understand there is more to an air filter inspection than looking for a dirty air filter? Make certain he understands the liability a damaged housing can be to the shop, especially if he fails to make the customer aware and properly document the condition on the repair order.

By Larry Hammer
Technical Services

Does your lube service technician understand there is more to an air filter inspection than looking for a dirty air filter? Make certain he understands the liability a damaged housing can be to the shop, especially if he fails to make the customer aware and properly document the condition on the repair order. We have seen vehicles leave the shop with damaged air filter housings. The tech was either not properly trained, observant, or he was afraid to tell the boss that he damaged the housing while making a filter installation.

Filter Replacement Intervals
If you look at the air filter replacement intervals recommended by the vehicle manufacturers, you will be amazed by the variations in vehicle mileage. Some recommend a filter replacement at 10K miles and others may vary from 30K to 50K miles. Personally, I am more concerned about the environment the vehicle has been operated in rather than mileage. Some turbo-diesel applications require an air filter replacement every 3K miles, especially those vehicles operated on construction sites or heavy farm use.

A Sealed System
Many technicians only focus on the condition of the filter. They are looking for contamination and the accumulation of debris that can restrict air flow into the engine. A close examination of the air filter housing and its ability to seal is imperative. Thoroughly examine for any evidence of dust bypassing the filter, such as dust trails across the filter seal or dust accumulating inside the air filter housing on the clean air side of the filter. Make certain all clamping devices are intact and the plastic latches are secure. Damage in this area should be discussed with the vehicle owner and documented on the repair order. If they refuse the repair, it would not be in the best interest of the shop to install a new filter, as engine damage is certain without the repairs.

A sealed system is especially important on vehicles equipped with a mass air-flow (MAF) sensor. The MAF sensor measures the amount of air passing through the sensor and provides data to the powertrain control module (PCM). Any air entering the system without passing through the MAF sensor is false air, which results in a deteriorated engine performance. Contamination of the sensor can affect the grams per second reading. Do not touch the MAF sensing element or allow cleaners, solvents or lubricants to come in contact with the sensing element, as they can render the sensor inaccurate or inoperative.

When making a filter installation, make certain all debris is removed from the filter housing. Examine the filter housing for deformity or damage from intense heat, which will allow unfiltered air to enter the system. Police cars and taxis have a history of distorted air filter housings due to the intense heat encountered during long periods of idling.

Diesel Applications
On diesel applications, a restricted air filter may result in a power loss, the air filter collapsing or coming apart and being pulled into the turbocharger. Sometimes the filter will lose its seal with the housing, or it gets pulled into the housing, allowing contaminates to be drawn into the engine, resulting in major turbocharger or engine damage. Some of the diesel applications make for a difficult filter installation, whereby damage to the filter or housing is easily incurred. Do not let the vehicle leave in this condition. Diesel air filters are reinforced for strength. If the correct filter is not installed, the filter will likely be shredded or sucked into the turbo. While there may be similarities, filters for gasoline applications cannot be interchanged with diesel applications.

Most diesel applications are fitted with a service minder to warn the owner or technician of a restricted air filter. Sometimes you will encounter a service minder that indicates a filter restriction, but an examination of the filter does not reflect a contaminated filter. Most often this is due to water or snow being pulled into the air intake. The water or snow seals the filter media and the engine will try to ingest the filter. This is usually evidenced by a deformed filter or the filter pulled from its mounted position. Making a filter strong enough to withstand the pressures of a restriction is not the solution, as it will result in a deformed air filter housing.

The tech must stay alert and be observant of any filter or housing damage.

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