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The Basics

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Coolants - The Basics

  • What is coolant??
  • Coolant is an essential item that helps prevent car trouble.
  • I've never seen it or heard of it...
  • Really!? Well, then I'll explain it to you.

What is coolant?

Coolant, also called antifreeze, is often referred to as LLC (Long Life Coolant) or SLLC (Super Long Life Coolant).

Normal water could also be used to cool an engine, but it would cause rust and would damage the engine if it froze. To avoid this, coolants with anti-freeze and anti-rust capabilities are used in automotive cooling systems.

The role of LLCs

Beyond preventing freezing, LLCs have a variety of effects that protect the engine.

  • 1. Prevent corrosion (rust) in the cooling system
  • 2. Prevent overheating
  • 3. Prevent freezing

Coolant types and concentrations

LLC (Long Life Coolant)
Anti-freeze with extended life
At Japanese automotive manufacturers, most are red or green.
SLLC(Super Long Life Coolant)
Anti-freeze given even higher performance and even longer life.
At Japanese automotive manufacturers, most are pink or blue.

The freezing point differs depending on the concentration. However, too high a concentration will actually raise the freezing point. In addition, in some cases, the anti-rust properties are insufficient if the concentration is too low.

  • 30%
    Guaranteed freezing point: Approximately -15°C
    Guaranteed freezing point: Approximately -35°C
    Dilute to the required concentration with water before use.

What is coolant made from?

Ethylene glycol is the main component.
Corrosion inhibitors, dyes, and several other ingredients are added to it.

Main application
Ethylene glycol
Main component to prevent freezing
Corrosion inhibitors
Several types are included in order to prevent corrosion in metals such as iron, aluminum, brass.
Included to ensure cooling performance
Added to make it easier to distinguish from oil and other liquids, and to improve visibility so the liquid level in the reserve tank can be seen.

What does a cooling system with coolant look like?

Example: Engine cooling system
  1. Cools the engine interior
  2. Heated-up coolant goes to the radiator
  3. 3. Dissipates heat to radiator surroundings, cools down
  4. 4. Returns to the engine*A water pump is used to circulate the coolant.

Causes and impacts of cooling system problems

Failing to make proper use of coolant can lead to a variety of problems...

(1) Appearance of rust / corrosion

  • Low quality ⇒ Using a low-quality (insufficient corrosion inhibition) LLC
  • Reduction in corrosion inhibition due to long-term use of LLC
  • Reduction in corrosion inhibition due to insufficient concentration of LLC
  • Use of water other than tap water
  • Appearance of rust
  • Metal corrosion
  • Scale deposits
Water pump malfunction
Formation of holes in engine block / radiator

(2) Overheating

  • Clogging of cooling system
  • Leaking of coolant due to rust / corrosion
  • Insufficient coolant
  • Improper coolant concentration
  • Deterioration of heat dissipation capability
  • Overheating
Engine seizure

(3) Freezing

  • Use of low-concentration LLC
  • Reduction in coolant concentration due to replenishment of tap water, etc.
  • Coolant freezes / Volume expansion
Damage to cylinder block
Damage to radiator
To avoid engine trouble,
periodic coolant changes and proper use are critical.

Each auto maker has their own recommended time period or distance guideline for periodic coolant changes, so be sure to check the criteria for when to change your coolant.
For example, Auto Maker A has the following guidelines.

First time: after 7 years or 160,000 km
Second and subsequent times: after 4 years or 80,000 km
*Whichever comes first