Head gasket

[1] Leaks in the head gasket can cause poor engine running and/or overheating.

Blue smoke from the exhaust suggests that excess oil is entering the combustion chambers (although there are other possible causes than a head gasket leak).

However, the presence of this substance is not conclusive proof of head gasket failure, since oil could mix with the coolant via other routes.

If coolant enters a cylinder, the burning of the air/fuel mixture is compromised, reducing the engine's performance and often causing steam (white smoke) to be visible from the exhaust.

When the combustion gasses leak out of a cylinder, this causes a loss of compression, leading to power reduction or rough running.

Most gaskets used in standard production engines can be critically damaged by severe detonation.

Head gasket (in dark gray with a red border) sitting on top of an inline-four engine block . When installed, the four large holes will align with the cylinders.
Head gasket with a leak between the rightmost and centre cylinders.