These are the aspects of maintenance related to the engine.

Engine Oil Engine Oil Filter Cooling & Heater System Radiator Cap Engine Coolant Drive Belts Air Cleaner Element Valve Clearance

Timing Belt (Chain) Spark Plugs Fuel Filter Battery Fuel Tank Cap PCV Valve Charcoal Canister Idle Mixture

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• Engine oil deteriorates by being used, or even if it is not used.
• Engine oil becomes dirty as it removes dirt and sludge inside the engine, and turns black.

• The engine is damaged and becomes difficult to start
• Continuing to add engine oil without performing an oil change leads to a decrease in oil performance shown in the left graph.

• Replace the oil according to the distance driven or amount of time because it is difficult to judge the deterioration by looking.
• Refer to the maintenance schedule because the replacement interval varies by model and usage conditions of the vehicle and by looking.

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This is the part that removes the carbon, sludge and metal particles in the engine oil.


If the filter is clogged, oil cannot flow through the filter. Then the relief valve opens and sends the dirty oil into the engine.

• Replace the engine oil filter according to the distance driven or amount of time because it is impossible to judge the level of deterioration just by looking on the surface.
• Refer to the maintenance schedule because the changing interval varies by model and usage conditions of the vehicle

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This system keeps the temperature of the engine constant. Also, the hot coolant warms the air to adjust the passenger compartment temperature.


Not only does it cause overheating, but also it damages the engine itself.

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It allows the coolant to stay at a constant pressure to keep the boiling point of the coolant above 100�C. Also, it improves the cooling performance by making the temperature difference between the coolant and the air greater.

The pressure valve opens at high pressure to deliver the coolant to the reservoir tank. On the other hand, the vacuum valve opens at decreased pressure to draw the coolant back in from the reservoir tank.

If it does not function properly, it causes overheating.

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• It plays these roles.
• It prevents the coolant from freezing.
• It prevents the parts of cooling system from rusting.
• It prevents overheating. (The boiling point is higher than water).
• If the coolant is not changed
• Its rust inhibiting property decreases, and the radiator, pipes, hoses, etc. become damaged

Replace the engine coolant according to the distance driven or amount of time because it is difficult to judge the level of deterioration just by looking at the surface.

• Replacement (on Corolla for general countries): every 40,000km (24,000 miles) or 2 years
• Refer to the maintenance schedule because it varies by model

1. TLLC (Toyota Long Life Coolant): red. 50/50 ratio with water
2. SLLC (Super Long Life Coolant) Premix: No need to mix with water.

Use the coolant mixed with water. However it freezes easily if it is not used in the appropriate concentration. Use the TLLC concentration appropriate for each region. Refer to the Owner's Manual for the appropriate concentration of TLL.

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Drive belt drives the auxiliary mechanisms such as the alternator, power steering pum, and water pump.

• The alternator stops operating, and the battery dies.
• The water pump stops operating, and it causes trouble such as overheating

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Removes dust, sand, etc. to clean the intake air to the engine.

The engine power output falls and fuel economy becomes worse as the amount of air taken into the engine decreases

• Clean or replace the filter according to the distance driven and amount of time because it is difficult to judge the level of deterioration by looking
• Inspection (on Corolla for general countries): every 20,000km (12,000 miles) or 2 years
• Replacement (on Corolla for general countries): every 40,000km (24,000 miles) or 4 years
• Refer to the maintenance schedule because it varies by model.
• When driving in sandy or dusty areas, the cleaning/replacement interval becomes shorter. (Because it becomes clogged faster)

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It ensures the proper timing of valve opening and closing even if each part expands because of heat.

It causes the symptoms such as abnormal noise from the engine (tappet noise).


It causes symptoms such as slight engine vibration

• Inspection / adjustment (on Corolla for general countries)
• Gasoline engine: every 40,000km (24,000 miles) or 80,000km (48,000 miles)
• Diesel engine: every 20,000km (12,000 miles)

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It transfers the rotational movement of the crankshaft to the camshafts in order for the valves to properly operate.

It hardens due to the heat of the engine, and this can lead to cracking or causing the teeth to shear off because of the rubber material.

The timing of the valve opening and closing is out of sync, and the engine stops operating. The piston interferes with the valves, and the valves bend.

• Replace it according to distance driven.
• Replacement (on Corolla with Gasoline Engine): every 80,000km
• Refer to the maintenance schedule because it varies by model
• Timing chain is not replaced periodically

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It sends sparks to ignite the air-fuel mixture which is compressed for burning.

• When the electrode wears, plug gap becomes greater
• Dirt (carbon) sticks

By the corner of the electrode wearing, a plug gap spreads out, the fuel economy becomes worse, and the power output falls.

• Replacement depends on the distance driven.
• It is also possible to inspect condition by looking.
• Inspection (on Corolla): every 10,000km (6,000 miles) or 1 year
• Refer to the maintenance schedule as it varies by model.
• It is not necessary to adjust gap of the platinum-tipped and iridium-tipped plugs however they need replacement at 100,000km (60,000 miles).

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It removes small impurities contained in the fuel through the filter.

When the filter is clogged, fuel volume decreases. Then problems occur, such as the loss of power output at high speeds, then a larger volume of fuel is required

• Deterioration cannot be determined by looking.
• Replacement (on Corolla for general countries):
  • Gasoline engine: every 40,000km (24,000 miles) or 80,000km (48,000 miles)
  • Diesel engine: every 20,000km (12,000miles) or 2 years

Refer to the maintenance schedule because it varies by model.

The interval should be 1/2 if impure fuel is used

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It plays these roles:

• It supplies electric power to start the engine.
• It supplies electric power to the electric devices.
• It stores electric power to start the engine again.

• The electroyte volume decreases, and battery cannot be sufficiently recharged.
• It deteriorates, discharges, and the charging capacity decreases

• Battery has both positive and negative terminals. If in contact with water, the terminals make an electrical connection and short circuit occurs.
• Vehicles or electrical parts are short circuited when the positive and negative terminals are connected in an incorrect way.

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It is a cap for the fuel tank.

• If the gasket is damaged, gas evaporates into the air.
• If the vacuum valve malfunctions, air cannot be drawn into the tank to replace the fuel used. Then, a partial vacuum occurs in the tank causing an indentation

In the fuel tank, some fuel vaporizes, containing a large volume of poisonous HCs (Hydrocarbons).

1. Gasket
2. Vacuum valve

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It is one of the control devices for the Emission Control, and re-burns the blow-by gas.

If the PCV valve is clogged, the blow-by gas is not taken into the intake manifold, and is released into the air. It also mixes with the engine oil and deteriorates the quality of oil.

Inspection: every 20,000km (12,000 miles) or 1 year

This contains a large amount of unburned gas (HC), which blows from the gap between the piston ring and the cylinder wall out to the crankcase.

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This device prevents evaporated gas from the fuel tank from escaping into the atmosphere.

When the check valve sticks, it stops operating correctly. Then the evaporated gas is released into the atmosphere

Inspection: every 40,000km (24,000 miles) or 2 years

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The air-fuel mixture is adjusted during idling to keep engine operation stable.

• Stability of engine operation decreases
• Discharged amounts of CO / HC increase

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