MG Tech – MGB Colling System Check

A sudden drop in temperature that we can expect at this time of year will quickly expose any deficiency in the engine cooling system of a classic car – so Roger Taylor advises a quick check now to avoid an unwanted break-down and potential serious damage to an engine.

The first place to start on the cooling system is the condition of all the water hoses, check for cracks or sections where the rubber has become hard and made be susceptible to failing in low temperatures.

Stains around securing clips may indicate that hoses have started to perish and are beginning to leak – while there test for the tightness of the clips.

At the same time don’t forget to check the heater hose and the heater tap or valve as the heater system may not have been used during the summer so any problem will not have been detected – the first sign of a problem could be steam issuing from the bonnet the moment you switch on the heater.

Operate the heater as part of a routine examination this winter and look for any leaks – the positioning of the heater tap on an MGB can lead to water dripping onto the distributor and causing an electrical failure – an early indication is staining on the distributor cap.

Next check that the fan belt is nice and tight and that the belt itself is in good condition and properly located.

While under the bonnet examine the external matrix of the radiator of any signs of damage or leaks – this will be most noticeable in the bottom tray in which the radiator sits.

Finally test for the strength of the anti-freeze in the cooling system – remember that it is advisable to maintain anti-freeze in the system all year round.

This can be checked using a hydrometer (available from most motorists centres priced around £10). This withdraws a test sample of fluid from the radiator, using a suction bulb, into a cylinder containing a float which records the strength of the solution. If the levels are low add undiluted anti-freeze, run the engine and then test again until the correct strength is reached.

If the fluid in the radiator is dirty or contains suspended rust particles the whole system needs emptying.

Some early radiators have convenient drain taps at the bottom whole to empty other radiators requires removing the bottom hose.

This can lead to water spillages so ensure you have a container to catch any fluid – spread a plastic sheet under the car as well as it will stop anti-freeze staining garage floors or driveways. Remember to dispose of used anti-freeze responsibly.

Re-fill the system with the correct strength of a good quality anti-freeze – the dilution level will be indicated on the anti-freeze container. An MGB takes around 2 litres of fluid while a Midget’s capacity is usually 1.5 litres.