Thermostat in open position
It’s not Rocket Science
But it is important to understand the workings of the cooling system.
Patrick ‘Cal’ Callaby, Workshop Manager at Celtic Manor Resort, offers some timely advice on keeping it in tip-top condition
H
aving written a little about the radiator cap and water pump
http://www.pitchcare.com/mag azine/the-cap-that-keeps-its-
cool.html I thought that the cooling system in general might be of interest. There are many engine problems associated with the cooling system that can be prevented by a little maintenance.
Why do we need a cooling system?
At 4000 rpm there will be 2000 controlled explosions per piston per minute, so a 4-cylinder engine will have 8000 of these explosions every minute, each one generating heat. Now, much of this heat is expelled via the exhaust system, but a great deal is absorbed by the engine block which is not all bad - an engine runs more efficiently when the coolant is around 190-210 degrees Fahrenheit. The oil is thinner and engine parts move more freely so there is less metal wear. Temperatures inside the combustion chamber ensure efficient vaporisation of the fuel, and more complete burning leads to reduced emissions, or in the words of an American friend, “more bang for your buck”. So, some heat is desirable but too much is not.
Let’s take a closer look at how it all works.
Since we are looking at the cooling system, lets start with the bit that does the actual cooling of the liquid coolant, the radiator. Commonly, nowadays, made of aluminium (but not always), it consists of a header tank and a bottom tank. The
header tank has an inlet port through which passes the hot coolant from the engine. The coolant now passes through a series of flattened tubes to the bottom tank. While passing through the tubes the coolant is cooled by a through-flow of air passing over the surface of the tubes. The flow of air is generated by the fan and this is usually driven by a belt from the engine crankshaft, the same belt (usually) powers the water pump.
In the bottom tank is an outlet port,
from where the coolant is forced back into the engine via the water pump to be heated by the engine, where it passes through the thermostat and begins its journey back to the radiator. A nice simple and straightforward cycle, not all cooling systems are this simple but let’s stick with this one for now. Some of the problems you can encounter in a cooling system that cause overheating are:
• Blockages inside the radiator • Blockages outside the radiator • The fan and/or pump not turning • Leaking coolant
Heated coolant Fins • Faulty thermostat
Let’s look at these problems one at a time starting with internal blockages. Blockages inside the radiator.
The engine should be run on a mixture of 50% Ethylene Glycol (antifreeze) and 50% water in most cases. The antifreeze contains inhibitors that help prevent internal rusting of the engine water jacket, rust particles will circulate in the coolant and settle in the bottom tank, when the engine is switched off, to accumulate as solid sediment and, eventually, block off the tubes in extreme cases, restricting or preventing the flow of coolant in the system. Using water only will result in salts forming in the radiator tubes through electrolysis; these will thicken the walls of the tubes and make them less efficient and restrict the flow of coolant so it enters the bottom tank far too hot. Another double whammy.
Blockages outside the radiator.
These can have a variety of causes and a common one is airborne debris, especially on rough cutters in dry conditions. Rear mounted fans “pull” air through a screen at the rear of the engine covers, airborne grass chaff will be sucked onto the screen preventing sufficient flow through the radiator fins. Finer airborne particles will be sucked through the screen and, over time, will accumulate around the tubes and fins, again cutting down on air flow.
Tubing
Introduce an operator to machinery and anything can happen, but let’s stick to overheating problems. He comes with his bag containing flask, wet
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132