The Slipped Sleeve or Liner
Coolant traveling through the water jacket wall can allow a liner to let go as the moisture works around it and the cylinder wall. Many thought this event was always the reason for which a liner will slip or drop but it is not always the case. A liner can let go and drop even if water has not come in contact simply due to the expansion/contraction physics that is occurring over time and was not accounted for in the design and build process of the block. By design, the liners are not a “wet liner” in that they are not in contact with water directly unless a pore in the water jacket has opened up. Once a passage in the water jacket wall has opened up, water then comes in contact with the liner and can eventually allow it to move or shift. Upon removal of the cylinder head, a technician can visually check that a liner for a given cylinder has indeed dropped but to know why, a proper pressure test must be performed. The test is usually done prior to fitting new head gaskets to insure the block hasn’t opened up making the repair useless. With cylinder heads removed, a pressure test of the block at temperature can reveal the presence of a crack or fracture.
Instances of a liner moving on its own was not as common in the earlier casted blocks (3.5, 3.9, 4.2) but rather the GEMS and BOSCH castings affecting DI, DII & P38. A liner over time will come loose from its pressed position and move up and down slightly with the stroke of the piston. Many ’04 DII’s experience this around 70K-100K we have discovered, making a pronounced tapping noise that sometimes will come and go, especially after the engine has reached operating temperature. No instances of overheating and no misfire codes, just an annoying racket. The clatter seemed to be coming from the top end of the engine but many technicians, including ourselves, thought this to be a failed rocker shaft or lifters but several thousand dollars later we realized it wasn’t.
The factory steel liners once installed are resting in the bore with no ridge or counter bore at the bottom of the cylinder. At the bottom of the cylinders, there are sometimes the remnants of a small lip left from the machining process that the liner will tap against but this physical instance differs from block to block. At the top, the liner meets the surface of the cylinder head which keeps it pressed at/below of the surface of the deck so if the liner starts moving, it has the ability to move freely in one direction, down, which in the below image you can see what might occur.
The liner comes loose in the bore and catches that small lip of the casting as referenced before. The aluminum is thrashed out as the steel liner eventually drops with the down stroke of the piston.
This design is a weakness in the Rover block which is addressed in every build we do. Fitment of a performance liner that is stronger, thicker, and recessed with the flange at the top. No up and down movement is possible.