How to Repair a Blown Head Gasket

  • 4-8 hours
  • Advanced
  • 50-200
What You'll Need
Socket wrenches and driver
New head gasket
Drain pan
Service manual
Torque wrench

The first sign of a blown head gasket might be the fact that you’re losing coolant and there are no obvious leaks. Repairs are a big job and that one you probably shouldn’t attempt alone unless you’re an experienced mechanic. If you’re not certain about carrying out a head gasket repair, it may be beneficial to employ a professional or get help from a friend who is used to working under the hood.

Step 1 - First Steps

The very first thing to do is to disconnect the negative battery terminal. This will ensure that you don’t suffer an electric shock when you replace the blown head gasket. With a drain pan in place underneath, open the valve and drain the radiator. Don’t let the coolant drain into the ground because it can be toxic. Instead, store the coolant in a sealed container and dispose of it responsibly.

Step 2 - Accessing the Gasket

Using wrenches, loosen all relevant bolts and remove the intake hose and the air box. Next, you’ll need to take off the compressor for the air conditioner. To do this, you’ll have to remove several bolts and when the compressor is free, lay it on it's side to give you access to the cylinder head.

With a screwdriver, loosen the clamp on the water pump hose and remove it. With this done, you can now get to the alternator. You don’t need to take off the entire alternator harness. Simply remove the bolts and lay the alternator on the radiator hoses so it’s out of the way. Disconnect all the lines that run to the air conditioner. You will now be able to fully access the cylinder head.

Step 3 - Removing the Cylinder Head

Open your service manual and pay close attention to the tightening sequence for the head bolts that hold the cylinder head in place. These are very specific and need to be loosened in the correct reverse sequence.

Step 4 - New Gasket

Remove the old blown head gasket and fully clean the cylinder head and engine block so the new gasket will sit cleanly on the metal. Put the new gasket on engine block, place cylinder head on top and tighten the bolts in the correct sequence. You’ll need to use a torque wrench for this job as the bolts need to be at a specific pressure which will vary from vehicle to vehicle. It’s vital that you do this properly or you’ll just find yourself with another blow head gasket.

Step 5 - Replace Components

Replace the components and reconnect the hoses in the order in which you disconnected them. Ensure that the alternator is tight enough to run as it should. Once everything has been tightly connected, fill with fresh coolant in a mixture of 50 per cent coolant and 50 per cent distilled water. Turn on the engine and allow it to idle until it reaches operating temperature. Leave to run for several minutes then switch off and check the coolant level and for any leaks.