Fledgling big end bearing knock
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17 November 2008
Fledgling big end bearing knock. This is a tough one as we need to catch the damage as quickly as possible before the main and conrod shell bearings rotate on the crank. We have had very good results if the damage is caught quickly i.e. the instant the knock is first heard. Most conrod shell bearing damage results from zero oil supply (a red oil light) or from a cracked cylinder head where the coolant water washes the oil off the metal surfaces; shell bearings silver and lead are the first to go, and the cylinder walls then heat up due to friction and eventually the engine can seize solid. So if a bottom end knock, which sounds like a constant thud, thud, thud, is heard (caused by either lack of oil or coolant water in the oil) stop immediately and do not drive the vehicle again until the problem is fixed. Then use RESTORE to try and repair the damage by running the engine very gently at first until some improvement is heard. If the parts are too far gone the noise will inevitably get worse and the parts will need to be replaced.
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