Drivetrain Basics: Engine & Transmission Symptoms and Maintenance

The intricate systems of moving parts, dashboard lights that seem to light up for no reason, odd noises, or vibrations are a common cause for concern if you’re not very familiar with vehicles and automotive repair. Even though ignoring obvious problems and continuing to drive may be your first instinct, failing to inspect and repair a damaged or failing part on your car can cause even more extensive and expensive damage. Understanding a vehicle’s engine and transmission systems and symptoms of problems in the drivetrain can help you be more aware of potential concerns and make diagnosing the issue easier. Below, we will explore the common powertrain components of your car, what they do, and what signs of failure may look or sound like to help you better understand and care for your vehicle.

Your engine and transmission use a system of electrical and mechanical parts that help create power and deliver it to the wheels to keep your vehicle moving. There are a few key components of your engine that require basic understanding, and once you’ve grasped the key concepts of how your engine operates, it can help you better conceptualize the entire system and its functions to assist you in diagnosing problems you may encounter.

Most drivers are aware of engine trouble when their Check Engine light illuminates on their dashboard — though this can be concerning, don’t fret. Any O’Reilly location near you can perform free check engine light testing to help you get the information you need to schedule an appointment with a shop or perform any needed repairs. It’s also possible for some engine issues to fail to generate an appropriate signal to turn on the Check Engine light, but you might notice obvious performance problems that can help you identify the source of the problem. You can also visit our How-To Hub for topics like what to do when a Check Engine light comes on and what causes engine misfires to the signs of a bad alternator.

Engine Air Filter

The efficiency and performance of a car’s engine also depends on a variety of factors, including the air filter. This multi-layered filter helps to trap and eliminate outside contaminants like road dust, debris, and more to prevent them from entering the engine’s air intake and causing damage. Your air filter is a common maintenance item that will need to be replaced regularly, and your owner’s manual will also recommend appropriate air filter replacement intervals. Depending on where you live or drive your car most frequently, the air filter may need to be serviced more often due to increased levels of dust or pollutants in the air, so it’s a good idea to check its condition at least at every oil change to determine if it needs to be replaced. Regular air filter replacement can help improve fuel economy and engine performance by ensuring that your engine receives as much clean air as possible during operation.

Oil Filters and Regular Oil Changes

Your car’s oil is incredibly important to the longevity of your engine and its overall performance. Meant to lubricate and cool internal components, motor oil helps protect your engine from damage and prolong its lifespan. It’s recommended that you check oil levels once per month, or more often if you see oil leaks or puddles beneath the vehicle. Not only does oil play a large part in your engine’s performance, but the oil filter is also integral to ensuring that your engine lasts as long as possible. An engine oil filter is meant to trap and eliminate debris before it travels through the engine. Oil filters should be replaced during each oil change, and oil changes may need to be performed more frequently than recommended depending on how you drive your vehicle. Help keep your engine healthy and running smoothly with regular oil and oil filter changes.

Spark Plugs & Ignition Coils

The spark plugs in your vehicle are crucial to starting and powering an engine. Spark plugs are meant to provide the spark that ignites the fuel mixture in the cylinders, generating the power needed to run the engine and drive your vehicle. Spark plugs receive the power required to create high-voltage electrical spark from the ignition coil or coils. Newer vehicles feature one ignition coil per spark plug, and are signaled by the computer to send voltage to the spark plug at the appropriate moment for combustion. Because of high performance demands and excessive use, both the spark plugs and ignition coils have a limited lifespan and may eventually require service or replacement. Decreased engine performance is an indicator that one or more parts in your ignition system may require inspection or repair, and servicing the ignition system as needed can help keep your car running exactly as it should.

Belts and Tensioners

The belts and tensioners on your vehicle’s engine, including the serpentine belt and timing belt systems, transfer power to accessory systems like your water pump, alternator, and power steering pump and keep the engine properly timed for peak performance and efficiency. A timing belt coordinates your engine’s crankshaft and camshaft(s) for smooth engine performance, and a serpentine belt uses power from the crankshaft pulley to charge the battery and power the electrical system, operate the air conditioning compressor, pressurize the cooling system, and more. The belts on your vehicle are designed to transmit movement and power, while the tensioners provide tautness for smooth belt operation and to prevent loose belts from causing performance problems. Without healthy tensioners and belts, not only will your engine’s performance suffer, but a failing serpentine belt or timing belt can cause larger issues for your engine and accessory system's performance. Normal wear and tear, exposure to heat, and constant demands can cause your car’s pulleys, belts, and tensioners to experience damage. Ignoring these issues can cause overheating, a lack of charging system performance, a loss of power steering, or even engine failure and stalling.

Signs of a bad timing belt:

• Ticking or odd noises heard from engine
• Rough idle
• Engine misfires or inability to turn over the engine
• Dropping oil pressure or RPMs
• Illuminated Check Engine light

Signs of bad serpentine belts:

• Cracking or belt separation
• Looseness, squealing, chirping, or slapping sounds
• Whining or screeching noises from front end
• Engine overheating
• Loss of power during acceleration
• Decreased steering or handling abilities

The rubber cooling system hoses on your vehicle are crucial to reliable engine performance, and are designed to withstand the high temperatures and pressure they experience in your engine compartment. Your car’s cooling system hoses move coolant to absorb heat from your engine and dissipate that heat as the coolant passes through the radiator. Most vehicles include upper and lower radiator hoses, but may include a variety of other cooling system hoses that carry coolant to and from the engine, radiator, or coolant reservoir.

These hoses are designed to keep your engine cooler and to carry hot coolant to and from the heater core to keep your cabin warm when needed. Constant use, age, and heat from your engine can cause rubber hoses to fail, crack, or separate, which can lead to a coolant leak or low coolant levels. Heater hoses and radiator hoses are susceptible to brittleness and wear over time, so if you notice any of the signs below, it’s a good idea to inspect your cooling system hoses for damage. If you’re still not feeling confident about your car knowledge, check out our helpful article on cooling system basics to help you get the foundation you need to better understand your vehicle.

Radiator

Your radiator hoses are designed to help transfer coolant to and from your engine, and transferring coolant to the radiator allows the heat of the engine to be absorbed and dissipated to prevent overheating. Radiators are designed with fins and a long, coiled tube through which coolant flows. As you drive, air passing through the radiator reduces the temperature of the coolant before it is cycled back to the engine via the water pump. Radiators can develop leaks, clog, or suffer damage or obstruction that prevents them from properly cooling the fluid as it passes through, resulting in engine overheating which could cause more serious engine damage if not addressed.

Signs of a bad radiator:

• Low coolant levels
• Coolant leaks
• Engine overheating
• Problems shifting or transmission overheating

Water Pump

Your water pump is integral to the performance of your cooling system and is designed to pressurize and transport coolant throughout your engine and radiator to keep your vehicle operating at the right temperature. Your water pump includes the impeller, which is effectively a turbine inside the engine’s water channel that creates pressure and moves coolant throughout the system. The water pump pulley also receives power from the crankshaft using a belt that spins the pulley and impeller. Water pumps, as well as their gaskets, impellers, and bearings, can fail over time due to constant use and heat exposure. Failure of the water pump on your vehicle can lead to a variety of serious issues, most commonly including coolant leaks and overheating. An overheating or improperly-cooled engine may not only affect your car’s performance, but can also damage the engine severely or lead to complete engine failure. If your water pump has failed or is leaking, it’s recommended you also replace the gaskets and seals during your repair to be certain that it lasts as long as possible and that your vehicle is free from coolant leaks. If you’re unsure if your water pump is causing the problems you’ve observed, be sure to read our article on why your car is overheating to help you better understand what parts may need to be inspected or repaired.

Signs of a bad water pump:

• Engine overheating
• Steam from under the hood
• Coolant leaks
• Squealing noises from water pump pulley

Thermostat

The thermostat in your vehicle’s engine or engine compartment is designed to open and close at set temperatures to allow coolant to flow to the radiator when appropriate. Thermostats remain closed when you start your engine to allow it to reach operating temperature more quickly, and once it does, open to allow coolant into the radiator for cooling. This continues the entire time you’re operating your vehicle, and if the thermostat becomes stuck in the open or closed position, it could have an impact on your vehicle’s performance or lead to overheating and engine damage.

Cooling Fans

Finally, the cooling fan or fans on your vehicle are used to pull air through the radiator when the vehicle is not moving or when a larger load is placed on the engine. Cooling fans may be electric or mechanical, and mechanical fans often include a fan clutch to prevent the fan from spinning when it is not needed and reduce the load on the engine. Electric fans are controlled by a relay, and often by the engine computer, to turn on at specific temperatures to pull air through the radiator. Failing cooling fans can cause engine temperatures to rise at idle, but you may see the temperature drop once your vehicle is moving again. You may also experience a fan that runs constantly, even after the vehicle is turned off, which can be an indicator of a damaged relay.

Your vehicle’s transmission is imperative to your vehicle’s movement, and requires proper maintenance in order to keep it performing at its best. The transmission helps send power from the engine to the car’s wheels, and keeps you operating in the appropriate gear to maintain your vehicle’s speed and engine RPM. In automatic transmissions, clutches, gears, and valves are used to help the car shift properly and smoothly — with the help of transmission fluid. Low levels of transmission fluid can cause performance issues and internal damage from lack of lubrication. A transmission fluid service isn’t as common as an oil change, but transmission fluid condition can be impacted by the fluid’s age, the level of fluid maintenance, and your driving habits. You can check the owner’s manual for your vehicle to find specifications on transmission fluid types and service intervals to help maintain and prevent your transmission system from premature wear or failure. In many cases, it is necessary to check transmission fluid levels when the vehicle has reached operating temperature to ensure that the necessary fluid is circulating and that the reading you take is accurate, but this information can also be found in your owner’s manual. Ignoring your transmission fluid levels or condition can cause serious issues and more severe damage to to the transmission if not addressed, and transmission leaks caused by dry or cracked transmission seals should be a priority repair to prevent low transmission fluid levels.

If you found this information helpful, be sure to read other topics on car basics like basic car safety information and understanding the basics of your car’s handling to get all of the car facts that every driver should know about their vehicle.