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G'day,
Recently my Pajero 2.5l DT engine developed a curious rattle that is not evident at low load but gets louder as the power is increased. The engine has done 100kks. I thought that it might be the small end bearings but on inspection they are fine.

Any thoughts.
 

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hi
it could be the big ends
thats what happend to mine i ran fine but when i rev it hard it ratles i replaced the bigends which were very worn and now its fine
 

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The big ends are the bearing caps (in 2 halves) that attach the conrod (the bit that joins the piston to the crankshaft) to the crankshaft and allow each piston to drive the crankshaft with low friction (they are lubricated with engine oil)... sometimes they are referred to as the crankshaft conrod bearings. They probably do the most "work" in an engine and the fit tolerances are very small...a couple of thosandths of an inch. However, if worn they usually are more prone to emit a knocking sound when the engine is under load at low revs, say when lugging up a hill (and the knocking sound reduces or disappears altogether when you are descending down the hill).

Kombibob...Does the rattling sound occur when you rev the engine when stationary...or only when it is being driven? If you have checked the small ends then you would have checked the big ends at the same time :thumbsup:

Have you changed the timing belt? This must be done after 6 years or 60k miles (whichever occurs first) because if it stretches or breaks (and they can do both) it will cause severe engine damage (4D56T motors are interference fit for valves and pistons...which means they occupy the same space periodically, but don't collide given the action and accuracy of the timing belt and correct engine timing). A stretched timing belt can cause the minutest of collisions at higher revs.

Good luck with the diagnosis.
 

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Another thought as to "rattle" at higher revs...loose flywheel or spiggot bearing worn (similar noise comes from the rear of the enginefor both of these and increases with revs).
 
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