Copy of TTEC 3206 Vehicle Technology

Engine diagram

Coolant Systems Q&A

Tuesday, August 13, 2013

Coolant system questions

1. What is the purpose of the water pump? Pumps the coolant through the engine using pressure.
2. How much energy is converted in to mechanical energy? 25%
3. What are the three ways of heat transfer? Convection, conduction, radiation.
4. What is the purpose of coolant? Anti freeze lowers freezing temp. raises boiling temp. lubricates the hoses and water jackets.
5. What are the main components of a cooling system. Radiator, Hoses, water pump, thermostat, heater
6. Why do we need flexible water hoses on the cooling system? As the engine runs it shakes, vibrates and moves around and firm solid pipes will stop the movement.
7. Why are coolant hoses reenforced?as the pressure builds the hoses start to bulge
8. How is the water pump driven? by pulleys on the pump and crankshaft drivn by a belt.
9. What is the water jacket? holes that are blasted into it and these form passage ways for the water to flow through and cool the engine.
10. What is the purpose of the thermostat? One way valve that when hot opens up and allows water to flow from the head to the radiator.
11. What is the purpose of the cooling fan? when idle-ing the fan turns on to pull cold air through the radiator.
12. Why do some cars have two cooling fans? Air Conditioning
13. On electric cooling fans, what switches the fans on and off? a temp sensor in the heads water jacket that switches on whe it reaches 90 degrees.
14. How does the temperature gauge work? the temp sensor in the head water jackets that works on resistance. When cold it has a lot of resistance and as it warms up there is less resistance as the particles expand and move apart.
15. Why do we have a radiator pressure cap? this keeps pressure in the cooling system, pressure raises the boiling point. When there is too much pressure it relieves the pressure from extra water into the overflow bottle and when there is not enough pressure a vacuum is created which sucks water back into radiator.
16. Why do we have a recovery bottle? store extra coolant and catches the overflow and lets water back into the system.
17. What is electrolysis? sparking of electricity using DC current to drive a chemical reaction, used for separating ores.

Engine Compression Test

Steps to testing the compression
Remove ignition leads
Remove spark plugs
Insert hose from the compression tester into the spark plug hole.
crank the engine for 5 seconds with foot flat
write down the reading of compression test
do the same test on the same cylinder but with a little bit of oil on the piston head, this is called a wet test
crank the engine again for 5 seconds
write down the reading of compression test
do the same for the next cylinder
if there is a 10 - 15% difference between cylinders there is a problem with the cylinder


Safety precautions
disconnect the ignition system
turn off injectors
do not drop spark plugs
do not insert hose further into the cylinder than what the spark plug would sit