My car ran hot so the vehicle was stopped and allowed to cool down. When cool, it wouldn't re-start. It has been confirmed that the block is okay. What is wrong?
The mechanic says...
There could be a variety of reasons why the engine will not start, and precise diagnosis is impossible without examining the vehicle. However, the following pointers may help…
Engine overheating can sometimes result in the cylinder head gasket failing, giving loss of cylinder compression and/or inter-mixing of the engine oil and coolant; and if this is the case the engine may not run at all. Check the coolant for signs of engine oil, and the oil for evidence of coolant contamination (a cloudy, ‘emulsiony’ appearance is a good clue). Note that the spark plugs could also be dirty as a result of the cylinder head gasket failing.
It could be that the excessive temperatures have resulted in failure of ignition/electronic components, or in coolant overflowing into electrical connections which in turn will be unable to function correctly. This may also give a no-start situation.
Although the block may seem okay, inasmuch as the pistons and/or crankshaft bearings may not have actually seized solid, if the engine has run out of coolant or oil, the temperatures reached may have been so high that the piston rings and cylinder walls could be seriously damaged. The engine may crank (turn over) on the key, but could still be too badly damaged to start.
The vehicle needs to be checked by a competent mechanic to establish whether the non-starting is due to an electrical component not operating (usually straightforward to fix), or to mechanical failure within the engine. In this case the unit will need to be dismantled for a full examination to be carried out.
