How to troubleshoot a blown or leaking  head gasket
(continued from 1/2)

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BEFORE YOU START
  • Be careful not to touch any hot part of the engine

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How to make sure of a head gasket leak before intervening (continued)

Combustion misfires at every cold engine start:
  • At every cold start the engine will be difficult to start, vibrate and consequent combustion misfire codes will be generated on one or two cylinders.
  • Clear the codes and wait until the next cold start and check if the combustion misfires occur again on the same cylinder (s).
  • The engine runs very well like if no fault of any kind is there after a few seconds.
  • This means that some coolant is infiltrating the cylinder during the engine stop which leads to a non-combustion of the gases, then engine runs normal like if no fault is there as soon as the coolant in the cylinder has been expelled to the exhaust.
You can confirm this assumption by removing the spark plug (middle) of a faulty cylinder on a cold engine and inserting an inspection camera in the cylinder. Make sure first that the tip of your camera is thinner than the spark plug thread (right):
Insert the camera in the suspected cylinder (left, cylinder #2 in this case) which will probably not be able to focus.
You do not need to have a clear picture anyhow, just check if:
  • You see the reflection of the LEDs (right) on your screen which indicates the presence of water (coolant).
  • You see a matt picture with no LEDs which indicates the piston is dry
Confirm the result if you see reflections by letting the camera lens touch the piston and then with your hand to check if there is water on the camera tip:
Repeat the same in a piston that never returned a combustion misfire code (like cylinder #4 in this case) and you will notice the picture remains matt, also the camera lens remains dry.

Applying a temporary fix to confirm even more...

You can then poor the contents of any radiator leak bottle into your radiator expansion tank and run the engine at idle for half an hour and fast idle for a few minutes. Make sure to follow the instructions on the bottle.

If the difficult cold engine start symptoms vanish, then you get one more confirmation that the head gasket is blown.
There are specific head gasket leak stop products but a radiator leak stop chemical should also do the job. It worked in this case and the fix allowed to buy time before dismantling the cylinder head and replacing the head gasket.

Such time is precious to allow for the purchase of the numerous spares required to replace a head gasket.

To note that leak stop products are not guaranteed to work every time. 
From our partners' stores:

Head gasket leak symptoms after removing the cylinder head

Once the cylinder head has been removed, it is even easier to diagnose a blown head gasket.
Simply inspect the cylinders for traces of corrosion on the cylinders that were returning combustion misfire codes and the absence of corrosion on the other ones.
Traces of corrosion are very clear on this cylinder wall. Rust is clearly seen above the piston stroke i.e. wherever the piston rings do not reach:
Buy your coolant tester or cylinder head gasket from our partners's stores: