After casting the engine block, cylinder head and intake manifold, various operations must be carried out during which it is necessary to make openings which are then closed with plugs.
In addition to the fact that the holes must be closed, these plugs have another important function, if the coolant were to freeze, the engine block, cylinder head or any other part through which the coolant flows would break due to expansion. The plug is now the weak point and will be pushed outwards, so you will only have to fit a new plug and damage will be limited.
If there is a leak around the cap or if it is weakened by rust, you will need to replace it. The plug is a fraction larger than the hole it is intended for and therefore it tightens, it should be tapped carefully, or pressed if possible.
WBX engines
2 pieces in cylinder head, 24.0mm
3 pieces in intake manifold, 24.0mm
Diesel engines
4 pieces in the engine block, 36.6mm
different number in the cylinder head, 24.0mm
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