85 – System Description
Coolant System
The internal engine cooling circuit has the following components:
- a coolant pump operated by the V-Ribbed belt
- the integrated coolant/oil heat exchanger
- coolant ducts within crankcase
- cylinder head
- intake manifold, where the coolant temperature sensors are located
- the coolant thermostat.
Coolant goes into the engine, driven by the coolant pump. Depending on coolant temperature, the
coolant flows at the coolant thermostat through the short circuit direct back to the engine, or through
the radiator, where it is cooled before returning to the engine through the oil/coolant heat exchanger.
At the thermostat there are two circuits connected:
- the small circuit, which is flown through as long as the engine is cold
- the radiator circuit, which opens as soon as a coolant temperature measured direct at the
thermostat is more than 80 °C (176 °F).
At more than 95 °C (203 °F) coolant temperature the radiator circuit is fully open and the small circuit
totally closed. The heating circuit is always open and helps in cooling.
An expansion tank with a silica reservoir gives the necessary corrosion protection. The expansion tank
has an overpressure valve installed which limits the relative pressure in the coolant system to max.
2.3 bar (33.36 psi). A low pressure valve is installed to protect the coolant system from negative
pressure.
The coolant reservoir allows the coolant to expand when cold, or allows the cooling system to draw
additional coolant as needed. The coolant reservoir also contains a low coolant level indicator
Components of the A/C System:
(For installation and maintenance details refer to the applicable Aircraft Maintenance Manual)
ï‚· Coolant radiator
ï‚· Cabin Air Heat Exchanger
ï‚· Coolant expansion Tank
ï‚· Overpressure Valve
ï‚· Low pressure Valve
ï‚· Silica Reservoir
ï‚· Coolant hoses
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