Sniff Out Car Trouble

     Print Edition: February 2013

We explain different odours that could help you identify a few common car troubles.

1. Sweet syrup
After the engine has been idling a while or possibly a few minutes after it's been turned off, you detect a sweet syrupy smell. In all probability, a coolant-containing sweetsmelling, but toxic, ethylene glycol- is leaking. The leak could be from the radiator or heater hose or due to a malfunctioning intake gasket or cylinder head. If you can also detect the odour outside the car, It could be from a leaky radiator cap or the radiator itself. A strong odour inside the passenger compartment could mean a faulty heater core (which heats the cabin of a vehicle). You could also have a blown head gasket, which causes coolant to mix with the fuel. If this is so, you will see thick, white, sweetsmelling smoke from the exhaust.

2. Burnt toast
An odour similar to that of burnt toast could mean that the electrical wiring has overheated and the insulation is burning (or melting). It requires immediate attention as the risk of a short circuit is very high. It generally occurs in the summer months when ambient temperatures are high. The smell could also be due to a loose connection, which has caused sparks and burnt the insulation. If left unattended, it could easily cause irreparable damage to the circuit or, in rare cases, lead to spontaneous combustion.

3. Damp cloth or mould
You turn on the air conditioner and get a whiff of what smells like damp mouldy cloth. This is probably because there is mildew growth in the AC, courtesy the moisture that did not dry up inside the air conditioner's evaporator. Turn off the air conditioner for a kilometre or so (on the move) and run the fan on high to dry out the system. If the air smells stale (without the odour of mould), then it's only water condensation. When the AC is on, water condenses and stays in the evaporator core housing. Again, the best thing to do would be to run only the fan to dry out the air conditioning system.

4. Fuel
You might get a strong smell of fuel in the car when the vehicle is parked. On cars with an old carburettor system, this is normal if it is shut down when the engine is still hot because of fuel afterboil (boiling after the engine has stopped) in the carburettor float bowl. Also, if you have attempted to start the car and failed a few times, it could be that the engine is 'flooded' with petrol.

But, modern cars have an evaporative emissions control system. So, a smell of fuel could mean something is wrong. Of course, it could be just a loose fuel cap or an overfilled tank. But, it could also be a leak in the fuel injection line or the fuel tank vent hose. If neither of this is the cause, then don't risk starting the vehicle as it might be a severed fuel line or a leak in the fuel injection system. The odour could also be from the exhaust pipe if the fuel mixture has too much petrol.

5. Burning rubber
An odour of burned rubber could be the result of a loose rubber hose resting on the exhaust assembly or because a belt has been shredded by a jammed pulley. (If a belt is loose or worn out, it produces squealing sounds.) Also, if you have used your brakes a lot (or hard), the brake pads get overheated and a similar odour is produced. This is normal coming down a steep hill. In these situations, downshift and use engine braking to save your brake pads. If you get the odour under normal driving conditions, you either have a dragging brake or you might have left the handbrake on.

6. Rotten eggs
The smell of rotten eggs could indicate a plugged or damaged catalytic converter or an air-fuel mixture with not enough air. The smell is hydrogen sulphide in the exhaust, which is produced by trace amounts of sulphur in petrol. It's supposed to be converted to sulphur dioxide in the catalytic converter. The effect is also produced if the fuel mixture does not have enough air to burn all the fuel, such as when the car is climbing a steep hill or after braking hard. Check for fuel injection problems or a malfunctioning catalytic converter.

7. Burnt paper
The smell of burning paper is noticeable at all speeds, particularly when you are working your way through the gears in quick succession or if you ride the clutch a lot. The reason being that the clutch plate is being burnt off as the clutch slips. The odour could remind you of burning newspaper. The friction material on the clutch plate is made up of a paper composition, which explains the particular smell. Stop riding the clutch and get the clutch replaced immediately.

8. Hot oil
The odour of oil when the engine is hot could mean it is leaking onto the exhaust. It is an acrid, burning smell that is earthy and more pungent than that of heating used cooking oil. If it's from a leak in the crankshaft seal, you will find oil on the pavement and the exhaust. A leaky valve might not leave a drip if the oil falls on the exhaust, vapourising immediately. Look for excessive smoke emanating from the exhaust.

9. Sulphur
Gear lubricants are designed to reduce friction, act as heat transfer agents and protect against corrosion. They may contain active sulphur. If the interior of the car starts smelling of sulphur, it could be gear lubricant leaking from the transmission. Look for an oily liquid under the car.

Of course, however handy these tips may be, it is not a substitute for regular servicing and maintenance. Adhere to the service schedule recommended by the manufacturer. Prevention is better than cure holds true even in the automotive world.

Courtesy: Auto Bild India

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