Water-cooled engines, unlike air-cooled engines, have a seal between the cylinder and the cylinder head. This gasket should never be reused. If you do, it will immediately cause coolant leakage and loss of compression. A diesel cylinder head should not even be put back in place without checking it, it must first be checked for straightness, in many cases it has to be machined. The difference in size caused by machining must be compensated for by a thicker joint. Gaskets are available in three sizes, from 1.40 to 1.60 mm standard thickness.
If the cylinder head does not need to be machined, this may have happened in the past. Therefore, do not throw away your old gasket immediately, but first check the dimensions indicated on the old gasket. On diesel engines, the gasket has one, two or three holes (see photo) that indicate the size. You will immediately know whether the cylinder head has been machined in the past.
If the cylinder head has to be machined but the thickest gasket was already fitted, then it is time to fit a new cylinder head, as further machining is no longer possible.
All gaskets are delivered per piece, for waterboxers (WBX) two are needed if both cylinder heads are removed.
Attention: In the early days of waterboxers the cylinder head was installed on the cylinders with only the rubber gasket. Later this proved insufficient and it was advised to use a liquid gasket in addition to the rubber gasket, this liquid gasket is mentioned in addition to the 1985 gasket. If Volkswagen even mentions it when ordering the gasket, assume that this is not advice but pure necessity. So don't use an alternative, but what Volkswagen prescribes (mentioned on the options tab); only then, a long and good seal is guaranteed.
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