Paul Messam, Gleaner writer

Kurt Dyer (left) jokes with his mechanic, Eddie Roye, as he changes a set of spark plugs along the roadway in South Ridge, Bull Savannah, St Elizabeth. - Photo by Noel Thompson

How to check your thermostat

The thermostat in your car, though small and inexpensive, is the main control centre for the entire cooling system. The two most common types are referred to as 'bellows' and 'pellet'.

According to Mike Jones, mechanic, almost all modern cars are equipped with the pellet type, which is far more suitable for pressurised cooling systems. The purpose of the thermostat is to trap coolant in a cold engine. When the engine reaches a temperature, the thermostat opens to let coolant flow to the radiator. In fact, the thermostat plays two main roles. It supplies adequate hot water for the heater and assures that the engine will reach its proper operating temperature as quickly as possible.

"While many car owners may think the thermostat is there only to warm up the inside of the car quickly, and save them from the winter chill (for those living overseas), its basic function is to regulate the temperature of the engine," said Jones.

check if thermostat works

If the thermostat valve gets stuck in the closed position, coolant is trapped inside the engine and the engine will overheat. If the valve gets stuck in the open position, the engine warms up very slowly, if at all. You can get an indication of whether the thermostat is working by removing the radiator cap (when the engine is cold) and inserting a thermometer into the coolant.

Start the engine and watch the thermometer. Keep squeezing the upper radiator hose. When the thermostat reaches the temperature at which the thermostat is supposed to open, you should feel coolant surging through the radiator hose.

1. Drain about half the coolant from the radiator with the engine cold.

2. Remove bolts holding the thermostat housing. Remove the housing.

3. Lift the thermostat from the housing. Hold the unit to a bright light. The thermostat valve must be closed. You should see no light passing around the valve. If the valve does not close, replace the thermostat.

4. Note the temperature reading on the thermostat. Thermostats are built to be fully open about 20 degrees above rated temperature.

5. Tie the thermostat to the centre of a wooden dowel. Insert a .003-in feeler gauge between the thermostat valve and housing. Tie a string to the feeler gauge.

6. Place the thermostat in a pan of water. The thermostat must be fully immersed, but it should not rest on the bottom or against the sides of the pan. Place a thermometer in the pan and heat the pan.

7. Pull the feeler gauge free when the thermometer shows that water is heated to the temperature stamped on the thermostat housing; plus or minus 5 degree. If you can't, replace the thermostat. The thermostat valve should be wide open when the water reaches 20 degrees above the temperature, give or take 5 degrees.

How to replace coolant hoses

Whenever it becomes necessary to top up the radiator frequently, consult your mechanic immediately. Experts advise that it makes absolute sense for car owners to get a thorough pressure test of the cooling system both before and after repairs have been completed. "The cooling-system hoses of your car should be checked frequently," advises Andrew Brown, an auto mechanic. "They should be examined for cracks, softness and brittleness."

There are four or five cooling-system hoses in a car. Two of them are radiator hoses. One delivers coolant to the engine, while the other transfers hot coolant from the engine to the radiator. The two hoses that transfer coolant to and from the heater are also part of the cooling system. Additionally, there may be a bypass hose from the water pump to the engine.

"Hoses are important to engine operation," says Brown, an experienced mechanic for over 30 years. "If a hose splits, allowing coolant to be lost, you will be stranded, since an engine without coolant will quickly overheat and seize," he adds. According to Edwards, for this reason, it is wise preventative maintenance to examine hoses frequently. He further explained that some car manufacturers even recommend that all hoses be replaced every two years to avoid an emergency situation. The mechanic advises that it is a good idea to carry duct tape in the car for temporary repairs if a hose does split.

Always inspect the hoses

Examine the hoses for cracks, softness and brittleness by squeezing each one firmly along its entire length. Hoses should be resilient and flexible. If cracks appear as you squeeze a hose, replace it. With the engine up and running, check hoses for bulges. A bulge signals that a hose is weak and likely to burst. So have someone sit in the car and race the engine as you examine the radiator hose.

If it flattens out, the spring inside the hose is weak. Replace the hose, since coolant flow is being curtailed. A collapsed lower radiator hose causes overheating during higher speed driving. Remember when checking the lower radiator hose, keep hands away from the fan, belts and pulley. DO NOT wear clothes that dangle. Now, as you check each hose, examine its clamps for coolant leakage. If a clamp is loose, tighten it; if distorted, replace it.

How to replace hose

To avoid burning yourself, replace hoses with the engine cold.

1. Drain coolant to below the level of the hose that is being replaced. If coolant is to be reused, drain it into a clean container. To avoid losing any coolant, push a length of clean hose over the radiator petcock and place the other end in a container.

2. Open the hose clamps, or cut them off if they are going to be replaced.

3. Pull the bad hose off its connectors by twisting and pulling. If the hose is stuck, slit it with a utility knife first.

4. Clean the metal connectors with a wire brush or emery cloth.

5. Slip clamps on to the new hose and push the hose on to its connectors. If the hose is tight and does not push home, soak it in hot water a while.

6. When the hose is seated, position clamps about 1/2 inch from the ends of the hose and tighten the clamps.

7. Pour coolant back into the radiator. Start the engine and let it run as you examine that system for leaks.

How to replace spark plugs

Your driving pattern is the most important factor in the life of plugs. The stop-and-go, short run, city driver should not expect too much mileage from those plugs. It makes sense to have the mechanic check the spark plugs every few thousand miles. They will last longer if they can be gapped periodically, and a check of this sort will reveal any malfunctions in the carburettor that may lead to poor gas mileage and impeded performance.

The spark plug insulators, which is the porcelain section that sits outside the engine, must be clean and unbroken. A crack in these insulators or a coating of dirt, grease, or salt can offer a convenient path for the high voltage to escape into the engine block without firing the spark plug. "This leads to hard starting, poor engine efficiency, and excessive fuel consumption," said Keith Austin, auto electrician. According to Austin, faulty spark plugs are the main reason engines miss when the car is rolling.

Removing spark plugs

Step 1: Use the correct tool for the job. Usually, a 13/16 or 5/8-inch hex spark plug socket, ratchet wrench and an extension are needed.

Step 2: Identify each spark plug cable with the engine cold. Write identifying numbers on strips of masking tape and attach the tape to the spark plug cables. This will facilitate correct reconnecting of cables to plugs.

Step 3: Grasp and rotate each spark plug boot, pulling it from the spark plug.

Step 4: Loosen each spark plug, with one turn only.

Step 5: Blow dirt and carbon from around each spark plug. Use compressed air, if possible. If compressed air is not available, aim the end of a length of vacuum hose at the area around the plug and blow through the other end.

Step 6: Remove each spark plug and examine its tip for any unusual condition. Incidentally, if a plug binds in the engine, but a few threads are exposed, drip some light oil on the threads and screw the plug back into the engine. Let the oil soak the threads before you try to remove the plug again.

Step 7: Do a compression test, with spark plug out of the engine, if you suspect that engine missing is being caused by an engine problem. If the plugs you remove are not worn, just dirty, they can be restored to service if you have a spark plug cleaner. If not, take them to the service station for cleaning. Remember, wipe plugs to get rid of dirt, moisture and oil. Clean wet deposits from the firing tips by washing plugs in kerosene. Use a brush to work the solvent inside the insulators. Then dry the plugs with an air hose. Spark plug tips have to be thoroughly dry so solvent does not cake inside the plug. This will cause misfiring.

Step 8: Using the gap adjustment tool of a spark plug feeler gauge, open the outside electrode of each plug enough to slip a spark plug file between the electrodes. Do not use pliers or any tool other than a spark plug tool or you will damage the plug. File the centre and outside electrodes clean. This requires only a pass or two with the file.

Use a small wire brush to clean threads, but do not touch the electrodes with the brush, you can cause a damage. Use a spark plug feeler gauge, no other type should be used. Ensure that you have the correct specification, that is, heat range, for your engine. You will find it on the emission control decal or in the service manual.

Next, you need to insert the correct-size feeler gauge and move it in and out between the centre and ground electrodes. Check the manufacturer's specs for the correct gap. If the gauge is too loose or too tight between the electrodes, use the adjusting tool to close or open the gap by bending the side electrode. Bending the centre electrode will damage the plug. Gap is set properly when you feel a slight resistance on the feeler gauge as you move the gauge between the electrodes. It is important to remember that electrode gaps of new plugs are not present at the factory. You must set the gap before installing new plugs.

Also, bear in mind that over-tightening plugs makes it difficult to remove them next time around. Not making them tight enough causes compression loss. Please … no 'over-tightening or under-tightening'. Do get it right.