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Cylinder Head Crack – what does this mean?

Written by maryp posted on Wednesday, February 22nd, 2012

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Cracks in a cylinder head are often blamed for a head failure, but it is actually a symptom of something else that took place that resulted in a crack. Overheating or thermal stress is the usual culprit of the cracked or warped cylinder head. Loss of coolant, (and continuing to drive in that condition) will result in severe overheating and damage to the cylinder head.

Metal will expand when it is heated, and aluminum expands at 2x the rate of cast iron. In some cases the aluminum head with the cast iron engine block actually undergo 2 different expansion rates. There will be a normal amount of expansion no matter what the engine configuration, but if the specs are exceeded, then it is probable that you have now damaged the cylinder head. Minuscule or larger cracks may be found between valve seats, between the spark plug cavity, between combustion chambers and sometimes even on the top of the head. (An overheat condition can also result in a warping of the metal, where the metal has deformed, but a crack is not yet evident).

The best way to prevent this from happening, is to always heed your warning lights. But, even before you get to that point, have your BMW, MINI or Mercedes checked out by a pro to determine if you have the correct coolant in your engine and whether or not it is still working at it’s optimum. Follow, at minimum the manufacturers maintenance schedule, and keep in mind that your intervals may be closer together if your car is an older or a high mileage vehicle.

Sometimes, clients mistakenly think that “coolant” is something that keeps their AC cold. Not! The coolant is what is used to keep the temperature of your engine from overheating. The critical systems need coolant to perform properly, and to prevent damage such as a cracked cylinder head. Your coolant becomes old and useless after time. Yes, it is still a liquid, but it will become “watered down” from condensation in your hoses, etc, after thousands of miles of usage, and the chemicals become less effective.

We test your coolant and determine whether or not it is time for a coolant exchange. No guessing, just the science! If necessary, the old coolant is replaced with the new, fresh and correct fluid for your beautiful BMW, MINI or Mercedes. Unfortunately, a cracked head or a warped head is an expensive proposition. Preventative maintenance and paying attention to those warning lights will go a long way in helping to avoid severe engine damage.

Happy Motoring!

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One response to “Cylinder Head Crack – what does this mean?”

  1. Natasha says:

    I have a Peugeot 308. The car overheated and the engine overhauled by a macanic. The head was scemed and head and block pressure tested.
    After everything was done, just before starting,will poring cooling into the radiator the water ran into the engine.
    We took out the damp prop and the engine was full of water.
    After checking we saw that the water comes out the head bolts were we also saw that the 3 middle bolts guide at the exhaust side were cracked
    What can cause it can it many be the mechanics fault that he overtaque the bolts

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