Repair 7

How to Replace the Head Gasket on a 1999 Mercury Mystique

Mercury Mystique was manufactured from 1995 till 2000 by Ford Motor Co. It is a compact family sedan that is powered by a 2.5L V6 Duratec engine, which produces 170 horsepower. The head gasket prevents oil leaks by sealing the gap between the cylinder head and the engine block. This engine rarely requires head gasket replacement. Replacing the head gasket is a complicated process, but it is nevertheless possible to perform the task at home.

Instructions

1

Disconnect the negative cable of your battery before performing any maintenance work on your engine to prevent electrical shock or accidental starting. Remove the nut from the negative post with a box-end wrench. Lift the cable from your battery, move it outside of the battery box and close the lid of the battery box.

2

Unscrew the water pump, unplug the lower radiator hose, take out the heated oxygen (HO2S) sensor, remove the camshafts and remove the 12 hydraulic lash adjusters.

3

Disconnect the coolant crossover tube and position it to one side. Remove the oil level indicator and tube. Disconnect the crankcase ventilation---or PCV---valve and hose. Remove the cylinder head with the exhaust manifold after unscrewing the cylinder head bolts. Remove the exhaust manifold from the cylinder head.

4

Discard the old cylinder head gasket. Clean all dirt, debris and coolant from the engine block cylinder head bolt holes. Failure to remove all foreign material may result in damaged threads, improperly tightened fasteners or damage to components.

5

Lay the new head gasket on the cylinder block.

6

Position the cylinder head and insert new cylinder head washers and bolts. Tighten the cylinder head bolts in six stages. In the first stage tighten the bolts applying 30 foot-pounds of torque. Then tighten them by turning the torque wrench an additional 90 degrees. In the third stage, loosen the bolts by 360 degrees---one full turn. Then apply 30 foot-pounds of torque again, followed by an additional 90-degree turn and one final 90-degree turn of the torque wrench.

7

Install the exhaust manifold. Connect the PCV valve and hose. Tighten the bracket nut. Install the oil level indicator. Install the 12 hydraulic lash adjusters. Plug in the lower radiator hose. Install the water pump and connect the heated oxygen sensor (H02S).