Audi 80 Quiz
Cooling System

Pressurized cooling system

In this manual: Cooling System
Technical Description — 39Engines — 41Exhaust System — 13Cooling System — 28Fuel tank and fuel pump — 12Air Filter and Intake Ducts — 13Mono-Motronic Injection System — 18Digifant Injection System — 19KE-III-Jetronic Injection System — 35MPI and MPFI Injection Systems — 32Clutch — 11Transmission and Driveline — 21Suspension and Steering — 33Brake System — 41Anti-lock brake system — 8Wheels and Tires — 13Body Electrical System — 35Ignition System — 24Lighting — 14Signaling Devices — 7Instruments and Auxiliary Equipment — 54Heating and Ventilation — 7Body Components — 18Troubleshooting — 6Specifications — 13
~1min read

At operating temperature, the cooling system is under increased pressure of 1.2 – 1.5 bar, which raises the boiling point of the coolant well above 100°C. This creates a certain reserve. The engine can reach operating temperatures above 100°C without the risk of the coolant boiling in the system.


The correct system pressure is maintained by the threaded cap of the expansion tank, which incorporates a pressure relief valve (1.2 – 1.5 bar) and a vacuum valve (0.06 – 0.1 bar). The vacuum valve admits air when the coolant becomes colder and thus occupies less volume.

Test yourself

A quick Audi 80 quiz: every answer comes with an explanation and a link to the manual page.