How to Deal with a Blown Head Gasket

Posted on: 3 May 2016

Head gasket failure can be an unexpected and rather expensive problem for your engine. Once your head gasket goes, it's only a matter of time before the rest of the engine follows suit. The following offers an in-depth explanation of why this happens and what can be done to fix it.

How and Why it Happens

Think of your engine as a gigantic Oreo cookie. The cylinder head is on top, the engine head is on the bottom and the creamy white filling in the middle is the head gasket. The head gasket's job is to prevent the engine coolant and oil from leaking into the combustion chamber while at the same time preventing exhaust gases from blowing into the coolant and oil passages.

Head gaskets can fail for a wide variety of reasons. Engine overheating is the most common reason—the head and block can expand and damage the head gasket if the engine overheats, pinching the gasket until it breaks. Pre-ignition and detonation can create enough exhaust pressure to break part of the gasket, allowing gases or coolant to leak through.

Common Blown Head Gasket Symptoms

  • Noticeable lack of power—A blown head gasket can cause an immediate loss of pressure in the combustion chamber, resulting in a noticeable loss of engine power.
  • Abnormal coolant loss—A blown head gasket may cause your engine coolant to mysteriously disappear over time. Keep in mind that low coolant levels can also lead to engine overheating.
  • Gray or white-colored exhaust—If coolant gets into the combustion chamber, it can cause your car's exhaust to turn gray or white in appearance.
  • Discolored engine oil—Head gasket failures can also cause engine coolant and oil to mix, resulting in the oil taking on a milk chocolate-colored appearance.

How to Replace a Blown Head Gasket

Replacing a damaged head gasket on your own isn't for the faint of heart. Not only is it a labor-intensive process, but the steps for doing so usually varies among makes, models and engine types. The following offers a generalized walk-through of the replacement process:

  • First, you'll need to drain the engine of its oil and coolant before removing the cylinder head from the engine block. Don't forget to dispose of the used oil and coolant in an environmentally friendly and legal manner.
  • Next, you'll need to remove the intake and exhaust manifolds from the cylinder head as well as the head itself. Depending on your engine's design, you may also need to remove the fuel rail, fuel injectors and camshafts before removing the cylinder head.
  • Once the cylinder head is removed, remove the old head gasket and carefully scrape any remaining chunks of head gasket material or sealant from the block.
  • Use a straight edge to check for any imperfections or undulations on the block and head surfaces that meet the gasket. If the block or head is deformed, you'll need a trained professional to either machine the surfaces back to spec or replace the head or block altogether.
  • Use a thread chaser to remove any lingering dirt or residue from the threads on the block. This will also prep the threads for the new head bolts.
  • Carefully place the head gasket on the engine block and make sure all of the holes on the gasket line up properly. Some engine manufacturers may ask you to apply liquid head gasket sealant on top of the gasket before reinstalling the head.
  • Replace the cylinder head and torque the head bolts according to the manufacturer's specified tightening sequence and torque specs. If your engine uses torque-to-yield bolts, you'll need to replace these with brand-new bolts before reinstalling the cylinder head, along with the intake and exhaust manifolds. Don't forget to add fresh oil and coolant to the engine once you're done.

Don't forget that you can always have an experienced mechanic tackle your head gasket replacement if you don't have the time or experience. For more information, click to read how you can ensure your car is working smoothly again. 


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