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

Work experience

Here is the work I do on Fridays as my work experience.

I changed the head gasket on a subaru legacy. I was able to use the hydraulic lift to lift a second car up and walk around underneath and remove the exhaust for removal of the engine.

Torque Settings

Your morning work "Torque Setting"

Hi guys, use the following web site to find the engine torque setting for the engine that we are current working on in the workshop

Engine make:  Mazda
Engine model: B6

Web Site:   www.autodataonline.co.nz/

Find out the follow torque setting

Cylinder head bolts
Rocker cover bolts

1. Camshaft pulley bolt   30nm, 50nm, 76 - 81nm
2. Spark plugs  15 - 23nm
3. Fly wheel bolts  100nm
4. Sump drain bolts 30 - 45nm
5. Sump bolts  10nm 
6. Main bearing bolts stage 1= 15 - 23nm stage, 2= 54 - 59nm
7. Big end bearing bolts stage 1= 25nm, stage 2= 50 - 54nm
8. Intake manifold to cylinder head bolts 20 - 25nm
9. Crankshaft pulley bolt 108 - 128nm

Answers to Questions

What is the purpose of a glow plug? Cold starts on diesels, warms the air inside the cylinder.

What does B.D.T.C means ? Before Top Dead Centre, this is about 5% - 16% before top dead centre

When the piston travel at T.D.C and both valves are close, what stroke is it? compression

How many time the camshaft turns in a 4 stroke cycle? 1 time

What is the purpose of thrust washers? any object spinning in a clockwise direction has a tendency to drive forward, the thrust washers allow the crank to spin without driving forward.

Name all the components of the valve assembly? valve, valve spring, collet, seals, retainer shield.

What is the purpose of the tag on the bearing shells? this stops the shells from spinning around the bearing, allows oil to flow through the little holes.

What compresses the volume of air and fuel? piston crown

Why is it important to time you engine up correctly? The piston could come up an hit one of the valves and break the valve. rough idle

What is a stroke? when the piston travels between BDC and TDC and vica versa

What drives the cams? camshaft, cambelt

What is the block made of? cast iron

Why is core plug fitted?

What is the purpose of the pistons? compress the air and fuel mixture and then when those get ignite the explosion force pushes down on the piston crown which goes down and turns the crankshaft.

What is the advantages of having aluminium head? better heat distribution, light weight.

Engine Technology

Internal Combustion Engine