Ask the Mechanic: Which tyres suit my car; XL or regular?

Hello Paul, I do not know whether my car needs XL or regular load tyres. The owner’s manual does not specify this so how do I find out?

Gloria

Hello Mukasa, having excessive amounts of engine oil after top up can lead to engine damage when you drive. This is because excess engine oil leads to unusual oil pressure build up, foaming and reduced lubrication efficiency or timely flow of oil around the engine. This can alter engine performance and protection.

Hello Gloria, Extra Load (EL) or Reinforced (RF) tyres are designed to carry heavier weight on the car than regular load tyres can carry. These tyres are built with special materials designed to withstand higher pressure should there be a need to inflate the tyres because of overloading.

You can find out if your vehicle should have EL or RF tyres by reading the user manual or checking whether the current tyres have XL inscribed after the tyre size. Professional tyre dealers may be able to help you identify whether which ones you need.

HOW DO I TELL A CAR IS FAULTY BEFORE BUYING IT?

Hello Paul, what should I look out for when buying a used car that has been on the road for some time?

Derrick

Hello Derrick, buying a used car that has been on our Ugandan roads (locally pre-used) can be as daunting a task as buying a used car from the bond. There are similar challenges one will encounter such as the need to establish the car’s service and repair history. One must look at whether the car has gone through its regular or periodical service actions to renew components such as fuel filters or timing belts. One must also know if the car has a major component overhaul or repair, for instance the engine or gearbox, which may add value to the car. It is also prudent to inspect the car for a possible major accident repair and evaluate its repair needs.

 Buying a locally pre-used car has a few advantages. For example, it will come tested, having been driven on Ugandan roads. If the current owner is a responsible motorist, they will have dealt with any major issues or service actions required when the used car left the bonded warehouse. A locally pre-used car may have some improvements or extras fitted by the current owner before putting it up for sale. A keen or enthusiastic motorist will accessorise the car with new mats, alloy wheels, tyres, audio CD entertainment and seat covers, among others.

Therefore, when buying a locally pre-used car. It is imperative to carry out due diligence checks such as confirming the true ownership of the vehicle. Sometimes, vehicles are sold without full authorisation of the owner by money lenders. You will find problems trying to transfer ownership of the said vehicle. In a worst case scenario, you may end up with a stolen car. Confirm with Uganda Revenue Authority, the local city authority parking fees or the previous owner whether the vehicle has no tax dues.

Request a road test and permission to let your mechanic examine the car and issue a mechanical status report. A look at the repair history, if available, will give you confidence to proceed. Also, try to ask why the previous seller is parting ways with the car in case the reason is a technical fault.

Get an expert to check if the car has an accident repair history. It is useful to establish the extent of the damage and quality of repair thereafter. A car involved in a severe accident and patched up or put together will never be the same again as it will have drivability issues.

Piston rings or camshaft, which is more important

Hello Paul, my mechanic says my car needs new piston rings and a new camshaft. This is such an expensive repair and I do not have this money at the moment. Can I do the two things separately?

John

Hello John, it is possible to separate the repair of your car engine piston rings and camshaft depending on the severity of damage for either components. Before you decide which of the engine components you will repair before the other, you need to understand their roles and what happens when they fail.

Piston rings are spring like seals that fit around pistons to allow them move up and down the different engine cylinder bores without allowing a cross flow of engine oil into the combustion chamber or pressurised fuel air mixture to the lubricant sump.

They help build compression (pressure increase) of the fuel air mixture ready for burning which helps to move the engine. Failure of the piston rings will cause loss of engine power, hard start, damage of ignition system parts such asspark plugs, cross flow of fuel air mixture into the lubrication storage or oil sump and at worst engine seizure as the cross flow alters the quality and performance of engine oil.

On the other hand the camshaft moves the engine valves in sync so as not to collide with the pistons. Engine valves allow air into the engine and exhaust out of the engine. When the camshaft fails the engine will misfire, make loud ticking noise, hard start and reduced performance.

It would be better to replace both piston rings and camshaft because they work together to give your car performance, fuel economy and protection.

WHY DOES A CAR STEERING SHAKE AT HIGH SPEED?

Hello Paul, my car steering shakes at speeds of 75 KPH and above. What could be the cause?

Darius.

Hello Darius, steering wheel severe shaking at speeds above 75 KPH can be caused by damaged wheels or tyres. Unevenly worn out tyres or bent rims will cause a wobble or vibration which increases with speed.

Tyre surfaces should be inspected for damage or uneven wear. Poor wheel alignment can cause steering shaking at high speeds as the wheels do not move unilaterally.

This can be ruled out at a wheel alignment centre. Occasionally, excessively worn out brake discs can cause steering judder or shaking at high speeds. Have them looked at if the other points check out fin.

ON STARTING MY CAR, IT SHOW LOW OIL PRESSURE

Hello Paul, whenever I start my car, it indicates stop engine oil pressure.....what do I do? It is a 2004 model.

Sara.

Hello Sara, you ought to engage a technician or mechanic to check the oil level and confirm the condition of the oil filter to rule out low oil level or blockage.

Confirm the condition of engine cleanliness or absence of severe sludge which could restrict oil flow through the oil pick up tube from the oil sump as well as the oil pump. Examination of the sump to rule out presence of sludge.

If that checks out then test the oil pressure switch which can give a false alarm if its faulty.

WHY DO I NEED AN ENGINE OVERHAUL YET IT WAS REGULARLY SERVICED?

Hello Paul, I drive 2001 VW Golf which I have been maintaining diligently. It has been running well until a couple of overheating episodes fixed recently. Over the last two or three months the Golf has developed excessive exhaust smoke first black and now white and loss of pulling power. I have to top up coolant and oil. Two different mechanics have suggested engine overhaul but cannot explain why the car has lost power and smokes yet I serviced it regularly. Can you explain why this car has deteriorated and what you think I ought to do?

Sam.

Hello Sam, from the recent history you have shared, your VW Golf engine may be burning engine coolant and engine oil. This means you have oil and possibly coolant leaking into the engine combustion chamber where it is burnt. This explains the white and blue smoke. Leaking oil also causes loss of compression when the pistons rise (compression stroke) to compress the fuel air mixture for combustion. The loss of compression, reduces the combustibility (ability to burn completely) of fuel and air in the cylinders hence the loss of power.

The mechanics have a point, you need to overhaul or replace the engine. The overheating episodes could have caused a damage of the cylinder head gasket and cylinder head which led to leaking coolant into the engine, hence the white smoke, typical of burning coolant.

Coolant in the engine will affect the lubrication of pistons and damage piston rings which can lead to oil infiltration into the combustion chambers.

An overhaul of the engine with new genuine parts is recommended after dismantling to assess the extent of damage. A quality used engine imported from the UK or Japan is another alternative.

The replacement engine has to get a compression test before you feel comfortable.

Send email them to: [email protected]