My car overheated and water escaped so I turned the car off immediately. Turns out the fan was broken. For my mechanic to diagnose whether the head gasket has blown he has to fix the fan, reservoir etc.

My question is, is it likely for the head gasket to blow from over heating. My car has never ever over heated before.



I would say it is unlikely so long as you 'turned the car off immediately'. There are measures you can perform before the engine is back to a running condition and may save the labour of installing a new fan only to remove it when more serious problems become evident with a running engine.

A compression test on each of the cylinders will determine whether the head gasket portion that maintains combustion and exhaust stroke compression has been compromised.¹

A cooling system pressure test will determine if the head gasket portion sealing the water passages has been compromised. This should probably be performed after the overheating in any event and the whole system examined for leaks.

One thing that many people ignore after suffering a catastrophic overheating event is removing the valve cover and re-torquing each of the head bolts in proper sequence. Overheating can change the torque on these very important bolts.

¹ A blown head gasket will typically leak rapidly; slower loss of compression may indicate valve or piston ring problems.


Severe damage may not occur to the engine if it is slightly overheated for a short time, but then again it could. One of the most common causes for head gasket failures is overheating. Overheating an engine is the most dangerous thing an engine will have to endure and will kill it like a temperature of 108 degrees will kill us. Overheating is caused by lack of coolant or lack of coolant circulation, lack of oil or oil pressure, or friction from worn engine parts. I would think that a cooling system pressure test and compression or leak down test could be done to check for a leaking head gasket. If the overheating caused coolant leaks elsewhere, all external leaks should be fixed before a pressure test is used do help diagnose a bad head gasket.

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