When comparing a car to the human body, the engine represents its "heart." The strength of this heart directly affects the vehicle's vitality and lifespan. However, just like the human body, the engine can experience fatigue and "illness." To understand and maintain it, we must break it down into several essential "vital systems": combustion, lubrication, cooling, and intake and exhaust. This article will use straightforward metaphors to provide an in-depth analysis of the common root causes of issues in these systems, along with systematic maintenance solutions.
Chapter 1: Lubrication System - The Engine's "Blood Circulation"
If fuel is the engine's food, then engine oil is its lifeblood. It creates a protective film between metal components, preventing wear while also dissipating heat and cleaning out impurities.
Common Problems and Root Cause Analysis:
Engine oil is not always effective due to the presence of various additives, which can be likened to the antibodies and nutrients found in blood. Over time, especially under high temperatures and pressures, these additives can become depleted. When the total base number (TBN) of the oil decreases, its ability to neutralize the acids produced by combustion diminishes, leading to internal engine corrosion. Additionally, short driving trips may prevent the engine from reaching its ideal operating temperature. This can result in fuel mixing with the oil, a condition known as fuel dilution. Much like blood that cannot perform its function properly due to dilution, this mixture significantly reduces the oil's lubricating ability. Furthermore, the water vapor produced during this process cannot evaporate, leading to the formation of sludge that clogs the oil passages, much like clogged blood vessels.
The oil filter, like the kidneys of the blood, is responsible for filtering impurities from the oil. However, it cannot completely remove even the smallest metal debris and dust. These micron-sized hard particles, circulating in the oil passages, continuously "microscopically scrape" critical parts like bearings and cylinder walls, causing silent but irreversible damage.
Over 70% of engine wear occurs at startup. This is especially true after an overhaul or extended periods of storage, when all oil on friction surfaces has flowed back into the oil pan. Starting the engine at this moment exposes metal parts to dry friction for a brief period, causing significant damage.
A systematic "maintenance plan":
The most effective way to maintain your engine isn't just by changing the oil based on mileage; it's through oil analysis. By testing the oil for metal content—such as iron, copper, and aluminum—you can identify which part of the engine is showing signs of abnormal wear. Additionally, by analyzing factors like viscosity and fuel dilution, you can assess the oil's true condition. This allows for maintenance to be performed as needed and helps prevent issues before they arise.
Before replacing old engine oil, use a specialized lubrication system cleaner and allow it to circulate through the engine at idle for 10-15 minutes. This will dissolve stubborn sludge and gum, allowing them to drain along with the old oil, creating a clean working environment for the fresh oil.
Before starting an engine for the first time after an overhaul or replacement, always use a pre-supply oil pump to introduce new oil into the lubrication system externally. Continue this process until the instrument panel or dedicated oil pressure gauge shows stable oil pressure. This crucial step helps prevent dry running during the initial start-up and significantly protects the engine’s lifespan.
Chapter 2: The Combustion System—Accurate "Internal Digestion"
It ignites the fuel-air mixture at the right time and in the right way, transforming it into pure energy that propels the vehicle forward.
Common Problems and Root Cause Analysis:
Carbon deposits are like a "blood clot" inside the engine. They not only cause incomplete combustion but also contribute to a vicious cycle.
Carbon deposits on the intake valve absorb fuel like a sponge, disrupting the precise air-fuel ratio. This leads to weak acceleration and increased fuel consumption.
In the combustion chamber, carbon deposits take up space, which can indirectly raise the compression ratio and create localized high-temperature spots. These conditions can lead to engine knock, characterized by an unusually intense combustion that produces a knocking sound. As a result, the engine control unit (ECU) must delay ignition and enrich the fuel mixture to protect the engine. This ultimately leads to a decrease in power and further worsens fuel consumption.
The engine relies on sensors to understand its surroundings. The oxygen sensor functions like a "taste bud," monitoring the oxygen levels in the exhaust to adjust fuel injection. Meanwhile, the air flow sensor acts like a "nose," measuring the amount of air entering the engine. Over time, as these sensors age and become contaminated from prolonged use, they can send inaccurate signals to the Engine Control Unit (ECU). As a result, the ECU may make incorrect decisions based on this distorted information, leading to issues such as excessive or insufficient fuel injection, all without triggering a fault light on the dashboard.
Systematic "Health Care" Plan:
Proactively "desilt" to break the vicious cycle:
For manifold injection engines, use a high-quality fuel additive that contains PEA (polyetheramine) regularly to effectively remove carbon deposits from the intake valves and combustion chamber.
For direct injection engines, the back of the intake valves cannot be flushed with gasoline, making carbon deposits more severe. Physical methods, such as walnut sand jet cleaning, are required to completely restore airflow.
For vehicles that often drive at low speeds in the city, it's important to consciously "drive high." This doesn't mean simply driving at top speed; rather, it involves operating the engine at medium-to-high speeds and under medium-to-high loads. For instance, once a month, while driving on the highway, try to maintain the engine speed at 3000-4000 rpm for 20-30 minutes while in manual mode or S gear. The increased temperature and strong exhaust flow during this time can help burn off and blow away some carbon deposits, effectively giving the engine a necessary aerobic workout.
When an engine experiences jitter or weakness, a repairman should not only check the fault code but also analyze the data stream while simultaneously monitoring multiple parameters. These include long-term fuel trim, ignition advance angle, and air mass flow. By understanding how these interrelated parameters work together, the repairman can, much like traditional Chinese medicine practitioners, "look, smell, ask, and palpate" to identify the root cause of the issue, rather than simply replacing a single part.
Chapter 3: Cooling System - Intelligent "Thermostat"
It maintains the engine operating within the most efficient and safe temperature range, preventing either a "fever" or "hypothermia."
Common Problems and Root Cause Analysis:
Coolant is more than just water; it plays a crucial role in preventing corrosion, boiling, and freezing. When its corrosion-preventing properties weaken, scale and rust can build up inside the engine's waterways and radiator. These substances have very poor thermal conductivity, effectively creating a barrier between the engine and the coolant. This barrier prevents heat from dissipating smoothly, which can cause the engine to operate at lower temperatures without notice, leading to decreased efficiency.
The thermostat regulates the circulation of coolant in the engine. If it becomes stuck in a closed position or is only slightly open, the engine may overheat. The water pump is responsible for this circulation; if the impeller corrodes or the belt slips, the flow rate will decrease. Additionally, if the radiator's exterior is clogged with insect debris and dust, and if scale buildup inside restricts the circulation, the radiator's ability to dissipate heat will be significantly impaired. Initially, these issues may not cause the water temperature gauge to spike, but they will gradually weaken the cooling system's safety margin.
Systematic "Care" Plan:
When replacing coolant, the most important step is to clean the cooling system. Using a specialized cleaning agent for a circulating flush helps dissolve scale and rust, which restores the thermal conductivity of the metal. This process is far more beneficial than just replacing the coolant.
After replacing the thermostat, use a diagnostic computer to read the coolant temperature data stream to observe whether it opens on time at the calibrated temperature (e.g., 87°C) and whether the temperature curve is stable after opening, ensuring that this "body temperature regulation center" is functioning properly.
For older vehicles or those often used in high-temperature and high-load conditions, upgrading to a large-capacity aluminum radiator and a high-flow electric fan is one of the most effective improvements. This upgrade acts like enhancing the engine's "cooling system," significantly boosting its stability and longevity in harsh operating environments.
Chapter 4: Intake and Exhaust System—A Smooth "Breathing Channel"
It draws in clean air and smoothly expels exhaust gases.
Common Problems and Root Cause Analysis:
A clogged air filter and carbon deposits on the throttle valve increase intake resistance. This forces the engine to work harder to "inhale," resulting in increased pumping losses, which directly manifest as increased fuel consumption and heavier throttle response.
The three-way catalytic converter is essential for cleaning exhaust gases, functioning like a "lung filter" in the human body. If it remains unused for extended periods due to issues like oil burning or engine misfires, it can become "poisoned" by unburned soot and metal particles. Additionally, it may become "sintered" and aged due to overheating. The failure of a catalytic converter is a gradual process, initially resulting in increased emissions. Eventually, severe blockage can occur, leading to restricted exhaust flow, akin to holding your breath, which results in a significant drop in engine power.
Systematic "Maintenance" Plan:
Replace the air filter strictly according to the maintenance schedule. In harsh, dusty environments, the interval should be shortened. Clean the throttle valve regularly to maintain unobstructed air intake.
Regularly inspect the front end of the three-way catalytic converter with an endoscope to check for blockages. A more professional method involves using an infrared thermometer to measure the temperatures at the inlet and outlet. Under normal operating conditions, the outlet temperature is usually several tens of degrees higher than the inlet temperature. If the temperature difference is too small, this may indicate inefficient internal reactions and potential failure.
For vehicles that meet China VI and later emission standards, it is essential to use low-ash engine oil, such as ACEA C-compliant oil. This type of oil produces less ash during combustion, which significantly prolongs the life of the particulate filter (GPF/DPF) and reduces the risk of blockages.
Final summary
Engine maintenance shouldn't be limited to mechanically following mileage schedules; it requires a comprehensive, systematic "mechanical life management philosophy." We need to:
Replace empirical judgment with oil monitoring and composition analysis, gaining insights into the health of this "mechanical life" from data;
Replace blind part replacement with real-time data streaming and fault trend analysis, deciphering its sophisticated "nervous system" signals;
Replace simple component replacement with performance-repairing cleaning and internal maintenance to clear metabolic blockages accumulated during operation;
Replace single-module operations with system-connected maintenance strategies to ensure the coordinated operation of the entire "mechanical system."
Only in this way can we truly understand this complex and sophisticated "mechanical heart" and ensure its robust, stable, and enduring vitality throughout its long journey.
