Diagnose your car problems by engine sound

Thursday October 10 2019
auto002 pix

Failure to fix the cause of certain sounds from the engine will lead to engine damage. Report the sounds to a mechanic who will then investigate the source and cause and have it fixed. Photo by Edgar Batte

Strange sounds from your car engine is one of ways you can tell that that something is wrong. Such sounds are common in cars that have been on the road for some time.
Beatrice Rukundo, a motorist, opines that it is sometimes difficult and challenging to determine the exact spot of the engine from the sound is emitted.

Knocking sounds
According to Peter Amadi of Dalas Auto Limited in Bunga, when your car has overheated due to, among other things, lack of coolant in the radiator, it will emit a knocking sound. If you do not look at the temperature gauge, the knocking sound becomes intense and the car will eventually stop. When the oil pump is dying and does not pump oil properly, it will also produce a knocking sound.
“If you do not fix the problem, the internal piece and main bearings of the engine will be damaged. It will mean that oil and pressure are inadequate hindering the engine from running smoothly,” Amadi explains.

Pinking or clicking sounds
Unlike knocking sounds, clicking or pinking sounds mostly occur when the engine is running. They sound as if the tappets have a problem especially when driving uphill or in traffic jam. It is a sign of bad or poor quality fuel. When you hear these sounds, it means the fuel does not burn well and dribbles in the engine cylinder head. You struggle with the accelerator pedal and the sound disappears thereafter. On a highway, the car will move normally.
To fix this, Amadi says you have to use high octane fuel to clear the bad fuel from the system.

Rattling sounds
This sound normally surfaces in the morning after the engine has been cold overnight. If it is a petrol engine, it could be that the spark plugs are not the right type to use in your car. It could also be that the heat is not within the right heating range or the lead wires or one of them is not working or that the air-fuel ratio is not matching. It will rattle for a few seconds or minutes and normalise after sometime. This depends on who serviced the car, what they did and what they put in the car.

“For diesel engines, it could be a diesel knock. It is when the injector nozzles are spraying too much diesel to the engine and making it sound like a serious knock. Your mechanic will have to carry out injector servicing and calibration of nozzles to remove nozzles and the injector pump and mount them on specialised machines to see and determine how much diesel each nozzle sprays. What the injector pump releases should be handled by the nozzle and give the engine the right amount of diesel. Instead of spraying too much or too little diesel, it should balance the pressure from the pump,” Amadi explains.

Failure to repair these sounds will lead to carbon build up on the cylinder head and insufficient combustion. You will also experience grinding valves and will build black soot on the valve stems which stays there for long. The black soot reduces fuel inlet into the cylinder and the fuel to air ratio will be too little that the car will not have power.

Loud squealing sounds
Alvin Jerry Nkini, a mechanic in Munyonyo, says if squealing sounds are heard as you accelerate, it could be that you are using a wrong air cleaner or wrong oil. The oil might be too thick that it cannot circulate in the engine until you accelerate harder using a lot of pressure. If the pressure is not applied, the carwill not move.
Every vehicle was manufactured to run with a specific air cleaner. It also depends on the air intake according to computer system that determines how much air and fuel mixture the engine needs. The ratio of fuel to air must be equal.


“Some motorists have Nissan air cleaners in Subaru cars. You find a bent air cleaner in form of letter C and is open on the inside. It means that your car is struggling to get air because the air is passing through the bend under pressure and cannot go through easily. Air cleaners and spark plugs must be the right ones prescribed for your car. The mistake many motorists make is fixing anything in their cars without first trying to understand what the car needs,” Nkini cautions.

If you do not fix the cause of these squealing sounds, the running of the valves and bearings inside the engine will be exposed to wear and tear. You will end up having to buy another engine or cylinder head. A second hand engine, for example for a Toyota Corolla costs between Shs2.5m and Shs3.8m depending on the engine capacity and the year, while for Subaru cars, a used engine will cost between Shs2.5 and Shs4m, also depending on engine capacity and age.

Grinding sounds
When shifting gears in a manual car, you might hear grinding sounds in gears one, two and three where the sound is loud. When you go to gear four, five and six, you will not hear the sounds because they are lighter. The car will not move the way you want it to move. In automatic cars, the sounds are heard when you are in a fast gear because the car needs more oil circulation, power and revolutions. If you do not repair the grinding sounds, you will have to carry out an engine overhaul to replace parts like the seals, main and piece bearings.

Engine overhauling is more expensive than buying a new engine. Sadly, the problem of buying a used engine is that you don’t know its mileage. The cheapest engine overhaul regardless of car brand, according to Amadi, is approximately Shs4m, except for Range Rovers which are more expensive.

Engine backfiring sounds
Backfiring depends on the engine firing order. A mechanic forget to put back either the plugs or lead wire or nozzles in the right place after fixing a car. They may put number one on four. When you misconnect wires, the cylinder will not work.

Cost of repair
In most cases, pistons rings are affected most by the above sounds. The fuel that drops in them is not burnt and this means the rings will stack in the piston. Fuel will start leaking into the sump.
With knocking, pinking and rattling sounds, your mechanic will have to look at them. It involves removing the engine to have them repaired and this may take two to three days to repair. To assess the crankshaft and other parts, the engine must be out.
On average, you will have to part with approximately Shs1.8m to Shs2m because most of the parts have to be replaced.