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Imbizo - Sharing Knowledge - Vehicle Components


Q: Why do I need to replace my fuel cap?

A: If your cap is missing, the crown is cracked or bent or the seal or gasket is cracked or worn, you need a new cap. Best to change the cap every 7 years of the vehicle life. The main reason to change the fuel cap is to prevent the fuel from vaporizing into the atmosphere. You could be without 83 litres of fuel over a one year period.

Q: What is a “ventilated” fuel cap?

A: The ventilated caps are designed to allow the controlled release of any pressure that may have built up in the fuel system, so that the fuel system is de-pressurised before the sealing gasket is lifted from the filler neck. This dramatically reduces the possibility of any fuel spillage from the tank to your hands or clothing.

Q: How do I know what fuel cap to buy?

A: Echlin follow the O.E.M design criteria and will have the exact fuel cap available. The Echlin catalogue also distinguishes between the ventilated and non-ventilated caps

Q: Why have non-vented fuel caps?

A: Non-vented fuel caps are designed to maintain the integrity of the fuel system. They do not allow fuel pressure to be released from the system, to conform with the introduction of emission control regulations. Thus used on vehicles from the year 2000 onwards. A non-vented fuel cap is recommended when your fuel tank is ventilated through the filler neck.

Q: Is it advisable to interchange radiator caps?

A: No, not recommended as the radiator cap is more than just a cap for your radiator.

It is designed to hold the coolant in the radiator under a predetermined amount of pressure. If it were not for this, the coolant would begin to boil. If the cooling system is under too much pressure, it can “blow its top”! To prevent this, the radiator cap has a pressure relief valve. The valve has a preset rating that allows the pressure to increase, up to a certain level: It helps to bleed the cooling system of trapped air by allowing air to pass into the radiator and released from the system.

Q: What is the lever type radiator cap?

A: The radiator cap is equipped with a lever that will, once lifted, channel the steam away from a person’s hands or face. By lifting the lever, steam is released under control with no coolant spillage.

Radiator Cap Modern Fuel “Non-Vented”


Q: Why should my engine have a thermostat fitted?

A: An engine needs to operate at a particular heat range to be efficient and to reduce the wear rate of engine components. This means that the coolant flow, within the engine, must be regulated.

Q: Is it good to remove the thermostat to stop the engine from overheating?

A: Removing the thermostat is not a good idea. It simply conceals an underlying problem. Have the cooling system pressure tested - an overheating engine could be caused by several problems: blown head gasket, cracked cylinder head / block, a clogged radiator, malfunctioning cooling system.

Removing the thermostat will simply result in cooler engine temperature whereby the engine will be insufficiently cooled in normal traffic flow but will overheat during slow traffic flow. A cold running engine will increase fuel consumption, as the engine CTS (coolant temperature sensor) will assume the engine’s not up to normal operating temperature, and simply inject more fuel.

Q: How frequently should the thermostat be replaced?

A: This is dependent on the condition of the cooling fluid as a system that had the correct anti-freeze/water mixture could see the thermostat operating up to 100 000 km.

Usually the thermostat is replaced when the engine temperature constantly moves above the indicator line on the dash board or when the ECU keeps on sending the high engine tempera­ture warning signal.

Q: How does the thermostat operate?

A: The secret of the thermostat lies in the small cylinder located in the centre section of the thermostat assembly.

This cylinder is filled with a wax that begins to melt at approximately 84° C (different thermostats open at different temperatures).

A plunger connected to the valve presses into this wax. When the wax melts, it expands significantly and pushes the plunger out of the cylinder, opening the valve to approximately 7.50mm.

Q: What does a jiggle pin do?

A: It helps bleed the cooling system of trapped air by allowing air to pass into the radiator and released from the system.

Jiggle pin fitted into the thermostat flange The anatomy of the thermostat
Thermostat Operation


Q: I recently had a radiator hose burst and

I lost all my antifreeze. Since warm weather is here I thought I would just run pure water in the engine for the summer. Will this hurt the engine and water pump?

A: Pure water will definitely be harmful to the engine and water pump. Antifreeze is also a coolant and is important in summer (warm weather) as well as in winter (cold weather).

Pure water will boil at approximately 94 degree celsuis. The best mix of water and anti-freeze is a 50% water to 50% anti­freeze. Antifreeze also reduces corrosion which could damage the water pump and prevent coolant to freeze during winter time. Different types of antifreeze exist, so be sure you use the type your vehicle manufacturer recommends and flush as required. Since antifreeze is a hazardous waste, recycle it according to local law.

Q: What will happen if my car only has water in the radiator and gets cold enough to freeze?

A: If it gets cold enough, the frozen water (since it expands) could crack the block, radiator, or water pump. You need to have the water drained and replaced with a 50% water to 50% antifreeze mixture.

Q: My car is dripping antifreeze around the water pump. What is the problem?

A: Water pumps have a built in “weep” hole. This is a spot that is built into the water pump that signals the car owner when the water pump’s internal seals have failed. When the coolant is leaking from this hole it is time for replacement. Take care in cleaning the complete cooling system to remove all debris like scull, rust and mud as debris will damage the new water pump seal shortly after start-up.

Q: Why are some water pump impellers plastic?

A: The material may appear plastic but it is actually PPS (Poly Pheneline Sulphide) an advanced semi-crystalline polymer reinforced composite. Echlin follow the OEM design criteria and will have PPS impellers on the water pump as per OEM requirements.

Q: Why may the water pump shaft break?

A: Incorrect fastening of the pump.
Incorrect alignment of the pump pulley in relation to the other transmission components.
Excessive tension of the timing belt.

Coolant Leaking from Weep Hole Absence of antifreeze in cooling system results in impeller to rust
Incorrect belt tension will cause shaft to break


Physical Address:
59 Merino Avenue
City Deep
Postal Address:
P.O. Box 86222
City Deep
Tel: +27(0)11 627 2500 Fax: +27(0)11 627 2600

Information kindly provided by Torre Automotive

View Also:

Vehicle Maintenance and Repair

Buying Quality Auto Parts and Safety on the Road 

Vehicle maintenance and safety guide to roadworthiness of vehicles

Imbizo: Know more about Shock Absorbers

Imbizo: Know more about Brakes


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