Cylinder Head Gasket Leaks

Cylinder head gasket leaks cause a variety of problems that no one is ready to deal with it.

  • Compression loss, (power reduction, or a rough engine). 
  • Excessive pressure, (exhaust gases in the cooling system). 
  • Engine overheating and increased engine wear, (motor oil mixing with antifreeze).

You can not see the gasket without disassembling the engine. this makes it very difficult to diagnose head gasket leaks.  Since a visual inspection usually will not prove a head gasket leak, it is important to know the other symptoms.

Blown Head Gasket Symptoms:

  • Coolant leaking externally from below the exhaust manifold
  • White smoke from the exhaust pipe
  • Overheating engine
  • Bubbles in the radiator or coolant overflow tank
  • White milky oil
  • Significant loss of coolant with no visible leaks

Usually one of these symptoms by itself is not enough to prove you have head gasket leaks, but if you have multiple symptoms at the same time it is likely that you have head gasket leaks.  It is important to drive your vehicle as little as possible if you have  head gasket leaks.

The hot gases and cold coolant moving through the hole in the gasket can quickly erode or warp the metal head or engine block leaving you with costly machining bills or even having to purchase new heads or a new engine.

Catalytic converter damage. 

catalytic converter
catalytic converter

Antifreeze entering the exhaust system can block the air passages by creating a heavy carbon soot that coats the ceramic catalyst. These heavy Carbon Deposits create two problems. First, the carbon deposits prevent the catalytic converter from reducing harmful emission in the exhaust flow. And second, the carbon deposits clog the pores in the ceramic catalyst and block exhaust flow, increasing back pressure and causing heat and exhaust to back up into the engine compartment.

If a large amount of coolant leaks, hydrolock can occur, causing extensive engine damage.

Cylinder Head Gaskets seal three different types of fluids:

  • Combustible air/fuel mixture
  • Water based coolant, usually with glycol admixed
  • Motor oil for lubrication

Apart from sealing the cylinder, the head gasket also seals water and oil passages between the head and block. Any connectivity between them will cause engine failure, or significant problems like burning oil (smoke from the exhaust). As a result blue exhaust smoke may be indicative of oil burning. White exhaust smoke is an indicator of coolant burning, another sign of head gasket wear.

Occasionally, the compression in the cylinder will cause a leak to form in the gasket and the gasket will have to be replaced. This problem has been magnified by the use of aluminum, while lighter than iron, aluminum has a much greater thermal expansion rate. Engine makers have responded to this by adding a non-stick coating such as Teflon to the surface of the head gasket.

white smoke
white smoke

Sometimes, all that may happen when a head gasket is blown is excessive steam erupting from the tailpipe. The engine may act and drive like normal, until all the coolant is gone and the engine overheats. In other occurrences, compression leaks into small spaces between the gasket and either the cylinder head or engine block trapping air that is then released when the engine is turned off, which then escape into the coolant and create air pockets.  So stay tuned as this will lead to a NEW Blog Post !

So there you have it !!
Because of the different material combinations in today’s engines head gaskets are going to blow. When they do have the work done by a professional who knows what to look for and can repair it correctly the first time.


About Danny Bender 168 Articles Is The Premier Automotive Engine Troubleshooting Resource Site. Shares Information On Engine Troubleshooting, Engine Rebuilding, Engine Repair Tips, Tech Info, Basic Machining, Automotive Testing, In Addition To Possible Solutions.