Chevrolet Trax: Belts (except timing belts)

On most older vehicles, the water pump is driven by a V belt or serpentine belt on the front of the engine that is also responsible for driving the alternator, power steering pump and air conditioner compressor. These types of belts are easy to inspect and replace if they are worn. You are looking for dry cracking on the inside surface of the belt.

On later vehicles, the water pump is often driven by the timing belt. This belt usually has a specific life expectancy at which time it must be replaced to insure that it does not fail. Since the timing belt is inside the engine and will require partial engine disassembly to inspect, it is very important to replace it at the correct interval.

Low belt tension, contamination and belt vibration are common sources of belt noise. A screeching or squealing noise that occurs when pulling away from a stop normally indicates a lack of tension; check belt tension and automatic tensioners.

A grinding noise can result from damaged bearings, which must be replaced, aligned and lubricated to eliminate the noise and further damage. Vibration and noise can develop over time as drive components such as pulleys and spring tensioners wear, bearings and brackets loosen, or belts wear and stretch.

Fig. 3: Typical Accessory Drive Belt

The angle between belt span and pulley is the critical factor responsible for causing the "chirp" associated with misalignment noise. The presence of high humidity (or a damp belt) often increases the likelihood for misalignment noise to occur. Misalignment angle can result from many different combinations of pulley positions - parallel and angular are two typical examples.

Fig. 4: Accessory Drive Belt Misalignment

Whenever a vehicle owner complains of belt noise, determine the type of noise and under what circumstances it occurs. The correction for a noise problem caused by belt misalignment is not likely to resolve a slip noise problem that may be caused by insufficient tension or other problem. The highest occurrence of belt noise due to misalignment comes from short belt spans entering large diameter pulleys. In the case of severe misalignment, repositioning of drive components may be required. Pulley alignment and tension must be correct for the drive to operate properly.

BELT TENSIONER

Belt tensioners are used to maintain constant tension on the belt, extending both belt and accessory drive bearing life.

NOTE: A tensioner cannot be rebuilt since internal parts are not available. Never try to disassemble a tensioner unit. Injury may result.

Fig. 5: Typical Accessory Dive Belt Tensioner

AUTOMATIC TRANSMISSION FLUID

Fig. 6: Crosssection Of Automatic Transmission - Typical

Automatic transmission fluid (ATF) is the fluid used in vehicles with a self-shifting or automatic transmission.

It is typically colored red or green to distinguish it from motor oil and other fluids in the vehicle. The fluid is a highly refined mineral oil optimized for the special requirements of an automatic transmission, such as valve operation, clutch and band operation, torque converter and gear lubrication. ATF is also used as a hydraulic medium in some power-assisted steering systems and as a lubricant in some 4WD transfer cases.

ATF usually contains an additive package with anti-foam additives, detergents and dispersants, anti-oxidation compounds, surfactants and petroleum dye. There are many specifications for ATF, such as the DEXRON and MERCON series, and the vehicle manufacturer will identify the ATF specification appropriate for each vehicle.

The vehicle's owner's manual will typically list the ATF specification(s) that are recommended by the manufacturer. Some manufacturers will recommend different ATF products for different kinds of vehicle use, such as frequent trailer towing or vehicles that are used for longer periods between routine maintenance.

Overused ATF often has reduced lubrication properties and abrasive friction materials (from clutches and bands) suspended in it; failure to replace such fluid will accelerate transmission wear and could eventually ruin a transmission. Color is not an indication of the service life of an ATF as most ATF products will darken with use. The manufacturer's recommended service interval is a more reliable measure of ATF life.

AUTOMATIC TRANSMISSION FLUID EXCHANGE & FILTER REPLACEMENT

Automatic transmission fluid lubricates, cools and cleans internal components of the transmission. It also helps to maintain the hydraulic pressure necessary for the transmission to function. The additives in the transmission fluid can be depleted over time and should be replaced following the manufacturer's recommended service interval.

ENGINE OIL

The temperature range the oil is exposed to in most vehicles can be wide, ranging from cold ambient temperatures in the winter before the vehicle is started up to hot operating temperatures when the vehicle is fully warmed up in hot summer weather. A "specific" oil will have high viscosity when cold and a low viscosity at the engine's operating temperature. The difference in viscosities for any single-grade oil is too large between the extremes of temperature. To bring the difference in viscosities closer together, additives called viscosity index improvers are added to the oil. This creates "multi-grade" oil which has the viscosity of the first number when cold and the viscosity of the second number when hot. This allows one type of oil to be generally used all year.

In engines, there is inevitably some exposure of the oil to products of internal combustion, and microscopic particles from black soot accumulate in the oil during operation. Also the rubbing of metal engine parts inevitably produces some microscopic metallic particles from the wearing of the surfaces. Such particles could circulate in the oil and grind against the part surfaces causing wear. The oil filter removes many of the particles and sludge, but eventually the oil filter can become clogged, if used for extremely long periods. The motor oil and especially the additives also undergo thermal and mechanical degradation. For these reasons, the oil and the oil filter need to be periodically replaced.

Most vehicle manufacturers utilize a time/mileage-based schedule. Time-based intervals account for both the short trip driver who does fewer miles, but builds up more contaminates, as well as the long highway trips that are much easier on the oil. Many vehicle manufacturers list somewhat higher intervals for changing of oil and filter, with "severe" service requiring more frequent changes. This generally applies to vehicles that are mostly used in "Stopand- Go" driving conditions; experience extended periods of idling; or used for short trips of under 10 miles, where the oil does not get to full operating temperature and other adverse conditions.

Some vehicle manufacturers have installed engine Oil Life Monitors using computer calculations to estimate the oil's condition based on the factors which degrade it. Conditions such as RPMs, temperatures, and trip length are factored in to the equation; and one system adds an optical sensor for determining the clarity of the oil in the engine.

Fig. 7: Engine Oil Life Monitor Display Example

AIR FILTERS

The engine air filter prevents dirt from entering the engine's cylinders, where it would cause mechanical wear and oil contamination. Most fuel injected vehicles use a pleated paper filter element in the form of a flat panel.

This filter is usually placed inside a plastic box connected to the throttle body with an intake tube. Older vehicles that use carburetors or throttle body fuel injection typically use a cylindrical air filter, usually a few inches high and between 6 and 16 inches in diameter, positioned above the carburetor or throttle body and may incorporate ducting to provide cool and/or warm inlet air, and secured with a metal or plastic lid.

A Pleated paper filter element is used for most automobile engine air cleaners, because they are efficient, easy to service, and cost-effective. The pleated-paper filter is sized appropriately for the airflow volumes encountered in a particular application and present only minor restriction to air flow until the filter has become clogged with dirt.

CABIN AIR FILTER

The cabin air filter is typically a pleated-paper filter that is placed in the outside-air intake for the vehicle's passenger compartment. Some of these filters are rectangular and similar in shape to the combustion air filter.

Others are uniquely shaped to fit the available space of particular vehicles' outside-air intakes. Clogged or dirty cabin air filters can significantly reduce airflow from the cabin vents, as well as introduce allergens into the cabin air stream.

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