Head Gasket Service Bulletin 1989 Porsche 911 Carrera 4 Coupe
Head Gasket Service Bulletin 1989 Porsche 911 Carrera 4 Coupe
When repairing oil leaks from the cylinder to cylinder head sealing area on engines prior to the above engine numbers, all cylinders and pistons should be replaced and all cylinder head sealing surfaces refaced. Cylinder head nuts are reusable. Importance notice : Replacement piston and cylinder sets have a groove to accommodate a seal between the cylinder head and cylinder mating surface (Figure 1). Effective immediately, only the steel sealing ring, Part Number 964 104 115 20 is to be used during repairs.
The cylinder heads must be refaced to accommodate the dimension of the new cylinders. Refacing can be done without cylinder head disassembly. Refacing of the sealing surface requires a lathe and use of special tool 9526. Machine 0.10 +/- .02 mm from inner surface (arrow 2 in Figure 4).
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