The Toyota Previa is a multipurpose vehicle which has been produced by Toyota since 1990 and was sold in the U.S. between 1991 and 1997. Despite its relatively low fuel economy, the Previa became a popular vehicle within the United States. If your head gasket becomes damaged, it can cause fluid such as engine oil and coolant to leak into the cylinder, which can cause considerable damage to your engine in the long term. Normally, this type of job should only be carried out by a professional mechanic, but if you feel you're up to the task, you can attempt it yourself.
Turn the engine off and let it cool down for at least an hour. Lift up the bonnet of your Toyota Previa van. Locate the battery. Use an adjustable wrench to remove the clamp bolt, which is fixed to the negative battery terminal. Pull the negative cable away from the terminal.
Locate the drain plug on the radiator. The plug will be at the very bottom. Place a drain pan directly underneath the drain plug. Remove the plug and drain the coolant into the pan. Once the radiator is empty, reattach the drain plug.
Use your wrench to remove the mounting bolts from the air filter unit, alternator and exhaust manifold. Lift them all from the vehicle and place them in a safe area, as you will need to reattach them later. Ensure you do not damage the parts in any way.
Use your hands to remove the coolant line and lower and upper radiator hoses from their connectors. Simply pull them out with your hands. Remove the mounting bolts attached to the timing belt cover and lift it from the engine. This will give you access to the head gasket.
Remove the bolts attached to the cylinder head, starting at the far left-hand side and working your way around in a cross-hatch pattern. Lift the cylinder head off the engine block and move to one side. Remove the damaged head gasket.
Install the new head gasket onto the engine block. Place the cylinder head back on top of the gasket. Reattach the cylinder head bolts to a torque of 23 foot-pounds using a toque wrench. Place the timing belt cover back in place with the mounting bolts. Insert the coolant line, as well as the upper and lower radiator hoses, back into their respective connectors.
Place the exhaust manifold, air cleaner unit and alternator back onto the engine and secure in place with the mounting bolts. Screw the radiator cap off the radiator and pour coolant back into the radiator. Attach the negative cable back onto the battery and secure in place with the clamp bolt.