Many car engine components are
now made as thermoplastic injection mouldings. This manifold
held temperature sensors in the coolant system close to the
cylinder head and began leaking after 5 years service. The
housing was secured by two bolts which compressed an 'O' ring
elastomer seal. This reduces the need for accurately matched
faces when an ordinary gasket is used.
relaxation by creep of the 'O' ring had occurred and
the original section was now quite flat and offered no
resistance to the clamping bolts. This caused the seal
to be inadequate against the pressurised water and a leak
A simple replacement of the 'O'
ring gave a cheap repair that should last another 5 years.