by minigirl » Wed Mar 12, 2008 1:27 am
in a word, yes!
well, what i did was i posted a query about the mgf on another forum and just waited for replies to come in - some of it went over my head too........ the general consensus though seems to be that if the repair last november was properly done and the uprated gasket was used, the problem should be cured.
given the direction this thread has taken, perhaps a few words about head gaskets wouldn't go astray:
the head gasket is inserted between the cylinder head and block in order to ensure adequate sealing between the two surfaces to prevent leakage of oil, coolant and combustion gases - and it is exposed to very high temperature and pressure. if the gasket fails, oil, coolant or combustion gases may to escape, leading to:
- loss of compression in turn leading to loss of power.
- loss of coolant, causing overheating of the engine.
- loss of oil, causing damage to the internal components of the engine.
- mixing of oil and coolant, causing the oil to emulsify.
needless to say, if you think your car has suffered a head gasket failure, you should switch off the engine and seek expert advice. you shouldn't continue to drive any car with a failed head gasket, as the resultant overheating can lead to warping of the head (which means more work and hence money is needed to fix it) and, in the case of the mgf, it can also result in softening of the metal, which may mean you have to replace the head rather than repair it...
i hadn't come across the term "thermal shock" before, but i suspect that it is probably most commonly encountered in cold climates during the winter months. engines need to reach a certain temperature before they operate efficiently, and the thermostat stops coolant circulating through the engine until that temperature is reached, allowing the engine to reach its optimum operating temperature as quickly as possible. when that temperature is reached, the thermostat opens and cold water (that has been sitting in the radiator) enters the cylinder head. this makes the head colder than the cylinder block. metal expands when heated and contracts when cooled. when the colder water enters the cylinder head, the head contracts slightly, while the block does not, leading to stresses on the head gasket. if the engine overheats for long enough, the stresses become so great that the gasket fails.
i hadn't heard of a pressure sensitive thermostat until a few days ago, so i can't really tell you much about them - i was just passing on some information i was given.....
as to the symptoms of head gasket failure:
- a sudden eruption of steam from the engine compartment may not indicate a failed head gasket. it could just be a leak in the cooling system. if this happens, stop the car and have a mechanic look at it. you may damage the engine if you continue to drive it after this happens;
- the same can be said of an increase of coolant temperature (indicated by the temperature gauge rising too far);
- loss of power and misfiring can be caused by a lot of things other than gasket failure. usual causes are either electrical faults or fuel blockages. you would have to ask a mechanic;
- hopefully you'll never see this on your car because it is a sure indication of head gasket failure but, if oil and water mix, you'll find that the oil filler cap will have a substance that looks like brown mayonnaise on the inside, rather than oil. not very nice.....
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