SECTION A
(a) What is the normal working temperature range for a water-
cooled automobile engine?
(b) (i) What is the main purpose of a thermostat in automobile cooling system?
(ii) Name two types of thermostat used in automobile cooling system.
(iii) Sketch one type of automobile cooling system thermostat and label three of its parts.
(c) State one merit of impeller assisted cooling system.
Observation
Candidates’ responses to this question were not good enough. The solutions to the poorly answered part of the question are given below
(a) Normal working temperature range for a water-cooled automobile engine
The temperature range is 77ºC - 85ºC
(b) (i) Purposes of thermostat in automobile cooling system
- To control the flow of water from the engine to the radiator until a predetermined
temperature is reached.
- Restrict the circulation of water in the engine until the engine attains its
operating temperature.
- To allow the engine to warm up quickly.
OR
- Regulate coolant temperature and circulation.
(ii) Types of thermostat
- Bellows thermostat or Bellow type
- WaxPellet thermostat,
- Wax element thermostat or
- Wax thermostat
(c) Merits of impeller assisted cooling system
- Positive circulation is faster
- A smaller radiator can be used
- Smaller bore pipes can be used
-It is lighter in weight
- Coolant level is not critical
- Reduced radiator height