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Engine cooling system doís and doníts...


The engine cooling system protects the most expensive part of your vehicle Ė its engine.  Itís therefore critically important to understand how to properly maintain the engine cooling system of your vehicle to ensure that it operates reliably and effectively.  This section outlines the doís and doníts that apply to the engine cooling system of your vehicle.  Since the engine cooling system operates at a high temperature and therefore has the potential to inflict serious injury, the most important issue to cover first is safety:


Avoid savage burns from the cooling systemÖ

NEVER remove the cap off of the radiator or the coolant reservoir directly after the vehicle has been driven and the engine and radiator are hot.  As the temperature in the engine and radiator increases, the pressure in the cooling system also increases greatly.  Removing the cap from the radiator when the cooling system is hot will see burning, hot coolant and steam immediately erupt violently from the radiator opening and burn you ferociously.  Removing the cap from the plastic coolant reservoir when the cooling system is hot could see the same thing happen.

Before taking the cap off of the radiator or the coolant reservoir, wait at least a couple of hours for the cooling system to cool down.  (Leaving the bonnet open will help to speed up this cooling process.)  After a couple of hours, since the cooling system will still be somewhat warm, use a thick rag doubled-over a couple of times in your hand to grip the radiator cap so as to protect your hand from being scalded.  Itís a good idea to also wear thick, chemical-resistant gloves as well and to even wear protective goggles to protect your eyes.

Loosen the radiator cap very slowly to relieve any pressure remaining in the radiator.  This takes longer than youíd expect.  When youíre sure that the pressure in the radiator has been fully relieved and equalised with the outside air pressure, then itís safe to remove the radiator cap completely.

Failure to observe the above warnings will more than likely result in serious injury, including possible blindness if the boiling coolant leaps up into your eyes when the radiator cap is removed while the radiator is still hot.  Boiling coolant is an extremely serious safety issue.  Please be extremely careful and avoid injury.

Because of the risk of serious injury from burning hot coolant, the best time to check the coolant level is in the morning when the vehicle hasnít been driven since the previous day and the cooling system, including the radiator, is stone cold.


Check the engine coolant level weeklyÖ

Check the engine coolant level weekly to ensure that there are no leaks in the cooling system.  Since the cooling system is a closed and sealed system, if you discover that the engine coolant level has decreased then there must be a leak somewhere, unless it has escaped through the overflow tube that is found on the plastic coolant reservoir of many vehicles.

The ideal time to check the engine coolant level is in the morning when the vehicle hasnít been driven since the previous day and the cooling system, including the radiator, is stone cold.  This enables you to avoid the risk of serious injury from burning, hot coolant.

If the radiator is cold, remove the radiator cap, since thereís therefore no risk of being injured by burning, hot coolant.  Check that the engine coolant level in the radiator is right up near the top of the neck of the radiator where the radiator cap screws on.  The coolant should be a rich, lime-green colour.  Coolant is highly toxic and highly poisonous so itís important that nobody mistakes it for lime cordial and drinks it.

Because engine coolant expands significantly as it heats up and contracts significantly as it cools down, the coolant level in the plastic coolant reservoir should be at or above the low mark on the reservoir.  If itís below the low mark on the reservoir, add coolant that has been pre-mixed in the correct ratio with distilled water to the reservoir so that the level increases to half-way between the low and full marks on the reservoir.  This allows for expansion of the coolant as it heats up when the vehicle is being driven.


Keep engine coolant mixed in the correct ratio in a plastic container in your vehicleÖ

Itís a good idea to keep engine coolant that youíve already mixed with distilled water in the correct ratio in a suitable leak-proof plastic container in the rear of your vehicle.  The kind of plastic water containers that come with a screw-on pouring spout and are designed for camping are ideal.


Use a high-quality engine coolant suitable for your particular vehicleÖ

Itís very important that you read the ownerís manual for your particular vehicle to determine which type of coolant your vehicleís engine requires or seek professional advice from your mechanic or from a qualified representative at your local automotive parts shop.  Given that there are different types of coolant which are based on different chemical formulations, itís critically important that you use the correct type of coolant thatís suited to your particular vehicleís engine.  Failure to use the correct type of coolant for your particular vehicleís engine could result in expensive engine damage.

The engine coolant protects the most expensive part of your vehicle, being the engine.  For this reason, itís important to use the highest-quality coolant you can find that is suitable for your particular vehicleís engine.  Nulon is one such manufacturer of high-quality coolant.  I use and recommend Nulon as trustworthy cooling protection for your vehicleís engine.  Itís never a waste of time to spend some time up front to select the best possible engine coolant for your particular vehicle, given that itís most likely going to protect it for a long time into the future.


Only use distilled water to mix the engine coolant to the correct concentrationÖ

Itís very important to only use distilled water when making up the mixture of coolant and water to the correct concentration.  Ordinary tap water has a lot of impurities in it such as chlorine, fluoride and dissolved solids such as heavy metals that will all react with the coolant adversely and impede its ability to protect the cooling system.

In contrast, distilled water has a minimum of these kinds of impurities and will ensure that the engine coolant is able to offer the cooling system its maximum possible protection.  You can obtain distilled water at your local supermarket or hardware store.


Mix the engine coolant with the highest allowable concentration of coolantÖ

Use the highest allowable concentration of coolant that the ownerís manual for your particular vehicle and the manufacturer of the coolant specifies for your vehicle.  This will ensure maximum protection of your engine against corrosion and overheating.

For example, if you find that the correct percentage of coolant for your particular vehicle is between 33% and 50%, mixed with between 67% and 50% distilled water, then itís best to use the highest concentration of coolant of 50% with 50% distilled water for maximum protection of your engine.


Replace the engine coolant every two yearsÖ

Replace the engine coolant every two years with a high-quality coolant suitable for your vehicle.  (Nulon is one such manufacturer of high-quality coolant.)  Itís best not to leave the coolant in the engine longer than this even if the manufacturer of the coolant says that you can in its instructions for the coolant.  The objective is to change the engine coolant before it becomes depleted and ceases to protect the insides of the engine from overheating and corrosion, not after.

Two years is a good service interval for the engine coolant.  To have to change it sooner than this would be an inconvenience.  To wait longer than two years to change it ignores the risk of the insides of the engine suffering corrosion from the water-based coolant which has become depleted of its additives over time, that are designed to protect the engine from corrosion.

I strongly advise against following the recommendations of manufacturers of Ďlong-lifeí coolant and leaving the coolant in your vehicle for more than two years before replacing it.  Itís good policy to change the engine coolant after two years as insurance against any corrosive damage that the coolant might cause to the engine if itís left in the cooling system longer than this.  Personally, Iím not at all convinced by the claims of Ďlong-lifeí coolant that their engine coolant can protect an engine from overheating and corrosion for four long years without being depleted and losing its effectiveness.

When replacing the engine coolant, itís important to observe the following points:

  • Itís very important to use a cooling system flush from a reputable manufacturer according to its instructions in order to clean the accumulated sludge and scale out of the cooling system.  Be sure to flush the cooling system with water from a garden house after it has cooled down completely to remove all traces of this cooling system flush before adding the new coolant.
  • Itís critically important to replace the thermostat and thermostat gasket with new parts as insurance against failure in the future.

    The thermostat is the most important component in the entire cooling system since itís responsible for regulating the temperature of the engine coolant to prevent the engine from overheating.  Itís very important to replace the thermostat when the opportunity arises from changing the engine coolant, rather than putting the thermostat back into service and taking the risk of it malfunctioning, which could result in extensive damage to the engine from overheating.

    It costs less in time and money to replace the thermostat during the scheduled maintenance of the coolant replacement before it fails than to replace it after it fails while in service.
  • Replace the top and bottom radiator hoses with new parts as insurance against failure in the future.
  • Replace the radiator hose clamps with new parts as insurance against failure in the future.
  • Replace the radiator cap with a new part as insurance against failure in the future.

    The radiator cap has a complicated spring-loaded sealing mechanism inside it which is susceptible to losing its effectiveness over time.

You can find complete and detailed coverage of all of the steps involved in replacing the engine coolant in the section titled, Changing the Engine Coolant.


Replace the radiator every eight yearsÖ

Itís a good idea to replace the radiator every eight years when the coolant is being replaced (ie. every fourth coolant change) with a brand-new radiator as insurance against the radiator failing while in service.  The radiator is critically important for protecting the engine from overheating and the expensive engine damage that often results.

Itís more economical and more convenient to replace the radiator every eight years with a new one before it fails when the coolant is being replaced, rather than wait for it to fail and risk the possibility of major damage to the engine due to overheating.  Thereís also the inconvenience of having to take the vehicle off the road for unscheduled repairs to the radiator and whatever else might be damaged as a result of its failure.

By simply replacing the radiator after eight years of service, regardless of whether itís still functioning correctly or not, all of these problems are avoided.  It costs less in time and money to replace the radiator before it fails during the scheduled maintenance of changing the coolant than to replace it after it fails while in service.


Ensure that the engine temperature gauge is working properlyÖ

Itís important to always ensure that the engine temperature gauge on the dashboard is functioning correctly.  While itís very important to minimise the chance of the engine overheating through proper maintenance of the cooling system, in the event that the engine does, in fact, overheat as a result of a coolant leak or any other reason, itís critically important that youíre able to detect this overheating quickly with an accurate and properly functioning engine temperature gauge on the dashboard.

If at any time and for any reason, you suspect that the engine temperature gauge is not functioning correctly, itís very important to get it fixed or replaced as soon as possible.  If your engine overheats when the engine temperature gauge isnít functioning correctly, you probably wonít realise that the engine is overheating until itís too late and the damage has already been done.

An overheating engine left unnoticed will very likely result in expensive engine damage such as cylinder-head damage.  The entire engine could also seize up so that it needs to be dismantled and reconditioned or replaced altogether.

The inconvenience and expense associated with an engine that has been damaged through overheating is enormous.  Any time and money you spend making sure that the engine temperature gauge functions correctly will give you the best possible chance of avoiding it altogether.


How to quickly cool an overheating engineÖ

If you ever notice that the engine temperature gauge needle is indicating a hotter engine temperature than normal or that the needle is indicating an overheating engine with the needle steadily rising, itís important to know that itís possible to cool the engine quickly by turning the interior heater on to the hottest setting and setting the interior blower fan to the strongest setting.  After doing this, pull over at the earliest opportunity and turn the engine off (to prevent further overheating) while allowing the heater and fan to remain on with the hottest and strongest settings.

This has the effect of drawing heat away from the engine since itís the heat from the engine which is used to power the interior heater.  With the ignition key in the position that allows accessories such as the interior heater, fan, radio and engine temperature gauge to function while the engine itself is off, you should be able to see the needle of the engine temperature gauge going steadily down as the engine cools.

After pulling over and turning the engine off, this is the quickest way to cool an overheating engine and to minimise the chance that expensive engine damage has occurred as a result of the overheating.  Finally, with the engine off and the heater and fan still running, you may as well open the bonnet to enable the engine to cool slightly more quickly.


Wash spilled engine coolant off of your vehicleís paintwork with waterÖ

If any coolant is spilled on your vehicleís paintwork, wash it off immediately with water to prevent it from damaging the paintwork.  Itís important not to wipe it off with a rag, because engine coolant reacts with the paintwork, making it soft so that wiping the fluid off could smudge and damage the paintwork.

In addition to having a garden hose close to where your vehicle is parked at home, itís quite useful to also keep a plastic watering can full of water next to the garden tap.  If any small spills occur such as engine coolant on your vehicleís paintwork, you can quickly use the watering can to wash them away.



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Copyright 2016 Andrew Mackinnon.  All rights reserved.