Thursday January 9 2014

What is the right tyre pressure for my car?

My Toyota Corolla had a heating problem in 2012 which was fixed by working on the gasket cylinder head. However, on 24 December, 2013 when I was traveling to the village I put on the air conditioner (AC) and the car suddenly started overheating and then stopped. After about 30 minutes I started and moved with no problem, but every time I put on the AC for about 30 minutes it would heat up.

On my way back I drove with no AC and with no problem at all. What could be the problem? Secondly, what is the recommended tyre pressure for a 185/70R13 tyre? My car has the inscription below on the door way and every mechanic I ask interprets the air pressure differently. What is the right tyre pressure?
175/70R13 82S
AE 2.0
CE 2.0
175/65R14 82S
AE 2.0
CE 2.0
Regards, Godfrey

Damage of the cylinder head gasket is often caused by overheating episodes. Your repair technician ought to have checked and confirmed that all components that cause over heating in the car’s engine cooling system are okay. When you switch on the air conditioning system it creates an additional consumer load on the engine. If the engine cooling system has a faulty or weak component it will overheat. Ask your mechanic to check that the thermostat opens on time.

The thermostat may be damaged by corrosion or age and will not open on time to let cool water through when the engine temperature is over 90 degrees centigrade, in which case you need to replace it with a new one. The water pump should be checked for coolant leaks or rumbling noise which suggests damage. Confirm that the radiator is not clogged by corrosion or leaking at the fins. The radiator cap should be checked for damaged seals. The cooling fan operation should be checked to confirm that it works. In case you have the electric fans confirm that the fan switch works and the fans change speed with the changing temperature.

It is important to ensure that the cooling system has no air lock as a result of repairs that involve dismantling of components.The recommended tyre pressure for your car as indicated by the manufacturer is 2.0 bars (approximately 30 psi) this tyre pressure is suited for the weight, loading capacity and body design of your car.

I enjoy reading your advice. I now need your opinion. My Audi A4 has a persistent steering problem. At low speeds such as 40-60 km per hour my steering shakes
violently. My wheels also shake. My mechanic has replaced the expensive front wheel hub bearings, checked the tie rod ends and carried out wheel alignment but the problem persists. What can we check now?

Your Audi wheel wobble may be caused by loose wheel studs, unevenly worn out tyres or damaged rims. Often the resultant wobble can actually damage the wheel hub bearings you have just replaced. You need to check that all wheel studs are tightly secured. Then visit the nearest tyre specialists and ask them to confirm that the tyre treads are not unevenly worn out in a manner that alters the normal wheel circumference. Check the inner and outer surface of your Audi’s
wheel rims to confirm that they are not damaged. This damage often results from unprofessional tyre removal from the rim by hitting it with a heavy pipe or hitting sharp potholes at high speeds. Bent rims are notorious for causing wheel wobble and should be replaced as soon as you confirm the damage. Lastly, in case your wheels pass the above two checks, confirm that they are balanced with weights on an automated wheel balancing machine. That should fix the wheel wobble.

I drive a Toyota Gaia. When I start the engine in the morning there is a knocking sound inside the dashboard just above the glove compartment. The sound seems to be made by one part repeatedly/rhythmically knocking against another, for about 15 minutes, even when the car is moving. Later the noise disappears. What is the problem and how can it be eliminated?
Twine S.R., Nsambya

The noise you describe under the dashboard of your Toyota may be generated by a faulty air vent flap motor.
This motor adjusts the air vent flaps during air intake from the cooling or heating system.
Whenever you start your car, this
motor runs one cycle to automatically adjust the vents. In the event that the attachments to the vent flap system disengage or break then the motor will run endlessly until it times out as it fails to complete the flapping cycle which should automatically stop the motor. No wonder you seem to hear the continuous sound of components colliding, which sounds like the vent flap motor continuously running the adjustment cycle against the disengaged or broken attachments. To rectify this situation you need a good car electrician to dismantle a part of the dashboard and access this component. Thereafter he will determine whether you need to repair the dislodged components or replace them.