Engine Cooling and Heating Systems

Engine Cooling

Process by which heat is removedRadiation, convection and conduction35% of total engine heat is removed by the cooling system

Cooling System Functions

Carries heat that is produced by the engine combustion process away from the engineHelps the engine to reach normal operating temperature fasterMaintains a constant temperature throughout the engine

Cooling System Functions

Picks up engine heat through conduction and carries it to the radiator where it is released to the atmosphere through convectionKeeps system under pressure to raise the boiling point and prevent liquid lose from evaporation

Coolant Flow

Standard FlowCoolant is drawn from the bottom of the radiator into the engineFlows through the water jackets in the block and up to the cylinder headFlows from the cylinder head out the thermostat and back into the top of the radiator

Coolant Flow

Reverse FlowCoolant is drawn from the bottom of the radiator into the engineThe water pump directs coolant through the water jackets in the cylinder head and down into the blockFlows from the block out the thermostat and back into the top of the radiator

Radiators

Components

TanksCoreFinsOil Cooler

Radiator Construction

TanksConstructed from copper, brass, aluminum or plasticCollects the coolant and transfers it through the tubes to be cooledReceiving tank contains baffles to help direct the coolant evenly over the tubesMay include an internal tank for automatic transmission fluid cooling

Radiator Construction

CoreTubes or fins made of copper or aluminumFins are thin sheets of metal that are soldered together to form channels for the coolant to pass through between the tanksMost are only a few thousandths of an inch thick

Radiator Construction

Core (cont)Tubes are either soldered or crimped to the tankThe number of cores is equal to the rows of tubes or fins (2 core, 3 core, 4 core etc.)

Radiator Construction

FinsIncrease air movement across the core to remove heat faster from the tubes

Oil CoolerCirculates hot transmission fluid through tubes surrounded by cooler engine coolant

Radiator Designs

Down-FlowCoolant moves vertically through the tubes or finsTypical of standard-flow systems moving from top to bottomBased on the principle that heat rises pushing hot coolant to the top and allowing cooler fluid to flow to the bottom (early systems w/o water pump)

Radiator Designs

Cross-FlowCoolant moves horizontally through the tubes or finsCommon on late model vehicles in both standard and reverse-flow systemsWorks well w/ modern low hood designsMore efficient cooling due to longer tubes (allows air movement over the tubes for a longer period of time)

Coolant Flow

Radiators

Radiator Failure

Leaks in the core from physical abuse

Radiator Failure

Leaks in the core from corrosion or electrolysis

Radiator Failure

Leaks between the core and the tank

Radiator Failure

Cracked or damagedtank

Radiator Failure

Leaking transmission cooler inside the tank

Radiator Failure

Damaged Fins

Radiator Failure

Plugged fins from foreign media

Radiator Failure

Plugged tubes from corrosion build-up

Pressurized Cooling System

Maintained by cap Pressure is determined by the cap’s rating15-17 psi gasoline engine7 psi dieselExcess pressure is allowed to enter the recovery (overflow) tank

During cool downVacuum created in the radiatorValve in the cap allows coolant to flow back from the recovery tank

Radiator Cap

APressureRelease

BVacuumCool-down

Coolant Recovery System

Recovery/overflow tankUnder atmospheric pressureStores expanded hot fluid Releases stored fluid back into the radiator during vacuum cool down

Coolant Recovery System

Expansion tankSealed and pressurized with the pressure capPurges air from the cooling systemMay have a bleeder valve

Coolant Recovery System

Air BleedLocated in a high part of the cooling systemUsed to purge air from the system when filling w/ new coolant

Radiator ServiceVisually inspect for leaks and external damage of radiator and recovery tankVisually inspect for corrosion build-up in radiator corePressure test to check for leaks

Radiator Service

Pressure test and inspect cap Inspect sealing surface of cap on the radiator neck for nicks or damageA failed cap can cause lose of coolant, overheating, collapsed hoses and component failure due to excessive pressure build-up

Radiator Service

Inspect shroud for damage and proper mounting

A fan shroud can increase cooling by 30%A failed or improperly mounted fan shroud can cause overheating and/or damage to the radiator core

Radiator Service

System BleedingAll air must be bled from the system after refilling with coolantMany systems include an air bleedMay have to loosen a hose at the highest point in the system to release all the air (heater hose)