I own a ‘53’ plate Ford Ka. In June of this year it had a new cylinder head gasket, water pump, thermostat and oxygen sensor, and the diagnostic aspects were checked. However, the engine fan is still coming on and staying on until I turn the engine off. At the weekend the red temperature warning light came on, the car cut out and smoke was coming from the coolant expansion tank. The oil was fine and there was water in the tank. Have you any ideas?
The mechanic says...
From what you say many possible causes of overheating have already been investigated. By the way, although it may look as if smoke was issuing from the expansion tank when the engine overheated, in fact this was probably steam caused by the coolant boiling.
Further components to have checked include the coolant hoses. It is not unknown for one or more hoses to collapse internally, although they may look fine from the outside. If a hose is restricted internally, the water flow around the engine will be reduced and overheating will result.
Similarly, the radiator core may be blocked, either externally (because of mud, leaves, etc. blocking the matrix) or internally, due to corrosion, limescale and other debris (silt) blocking the fine tubes that run through the radiator.
The radiator can be assessed by a specialist, or a competent mechanic should be able to assist with this and the hose checks. Sometimes radiators can be cleaned by ‘reverse flushing’ (that is, passing water through them in the opposite direction to normal coolant flow). However, if the material within the radiator tubes has solidified, a replacement radiator will usually be the most cost-effective answer.
If it is found that the radiator is blocked, in the future (after cleaning the original radiator, or fitting a replacement), it is wise to use de-ionised or distilled water (rather than tap water) to mix with the anti-freeze solution for use in the cooling system. Tap water is often ‘hard’ water, resulting in harmful deposits of limescale within the cooling system.
