* Head gasket failure: This is the most common and potentially costly problem. Over-tightening stretches and potentially cracks the cylinder head or distorts the engine block. This leads to leaks between the head and block, resulting in coolant leaks, oil leaks, and compression loss. The engine may overheat, lose power, or even seize.
* Cracked cylinder head: The cylinder head is made of aluminum, a relatively softer metal. Excessive torque can crack the head, requiring replacement—a very expensive repair.
* Cracked engine block: In severe cases, the force of over-torquing can crack the engine block itself. This is usually a terminal failure, rendering the engine unusable.
* Stripped threads: The threads in the cylinder head or engine block can be stripped, preventing the bolts from tightening properly or even seizing in place. This necessitates specialized tools or even professional repair to remove the damaged bolts.
* Bolt breakage: The head bolts themselves might snap under the excessive stress, leaving pieces embedded in the engine.
* Warped cylinder head: Even if it doesn't crack, the cylinder head might warp, leading to uneven compression and eventual head gasket failure.
In short, over-torquing head bolts is a serious issue that can lead to costly engine damage or complete engine failure. Always consult your vehicle's repair manual for the correct torque specifications and follow them precisely. Using a torque wrench is essential to avoid this problem. A properly calibrated torque wrench will greatly reduce the risk of over-torquing.
