THE COOLING SYSTEM

Purpose

• To regulate the engines internal temperature

• To remove excess heat from the engine

• To provide heat to the passenger compartment

The Water Pump

• Centrifugal-type, rotates faster than crank, up to 10,000 gal. per hour

• Pulley driven, belt, chain drive or direct drive

The Cooling Fan

• Provides air flow with vehicle stopped

• Provides increased air flow at low RPM or vehicle speeds

• Belt driven or Electric

Belt Driven Cooling Fan Clutch• Limits actual fan speed

no more than 2000 rpm• Engaged at low speeds• Disengaged at high

speeds• Thermostatic (temp.

sensitive)

Flex Blade Fan

• Fan blades flatten out at high speeds, reducing noise, increasing horse power

Electric Cooling Fan

• Electric – 12v DC motor driven fan

• Controlled in several ways– Engine coolant temp (ECT)

switch– A/C select switch– PCM controlled based on

various inputs

• Fan turns on/off at specific temps.

Electro-Viscous Fan Clutch• PCM Controlled fan

speed• Sensors monitored to

control speed:– ECT, A/C request,

VSS, IAT, Trans Fluid Temp, AAT

• Solenoid controls fluid flow, regulating fan speed

• Internal hall effect sensor monitors fan speed

The Radiator

• Transfers heat from coolant to the atmosphere

• Two types – Vertical & cross flow• Aluminum, brass, copper core;

brass, copper or plastic tanks• Air movement through radiator

created by a mechanical fan or by vehicle movement (ram air) dissipates heat

How a Radiator Works

Radiator Pressure Cap

• Regulates pressure in the cooling system

• Rated in psi – always replace with same rating

• Pressure valve – allows liquid or vapor to escape

• Vacuum valve – as system cools, coolant can reenter the system

The Thermostat

• Regulates engine coolant temperature

• Rated in degrees – 195 degrees most common

• Solid Expansion design – wax pellet expands as temp increases, valve begins opening at rating & is completely open within 20 degrees

Coolant

• Provides freeze & boil over protection, corrosion prevention & good heat transfer

• Ethylene Glycol based – recommended 50/50 mixture with water, poisonous

• Dex-Cool – used by GM, 5 year 150,000 mile protection, doesn’t contain silicate & phosphate additives

The Heater Core

• Small size radiator located in the dash, coolant circulates through it. A blower motor passes fresh air over it, heat transfers to the cooler air and into the cabin

• Many vans & SUV have rear heating units

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Overview