We have a '95 V6 MPV and the engine has started to make a loud
tapping/knocking noise, usually when cold. The noise dies down after
the engine has got up to temperature and also stops at higher revs...
can anyone tell me if the noise is the lifters (see videos below)? Many
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ALWAYS START WITH CHECKING FLUID LEVELS AND CONDITIONS.THIS ENGINE SHOULD BE A NISSAN BUILT V6 OVERHEAD CAM DRIVEN BY A TIMING BELT.ENGINE BEARING FAILURE NOISES USUALLY INCREASE WITH ENGINE RPM.IF STARTED IS SUSPECT THEN FIND SOME MEANS OF ROTATING ENGINE AT FRONT CRANK PULLEY,GRABBING LOWER PULLEY BY HAND AND TURNING OR SOCKET ON CRANK PULLEY CENTER RETAINING BOLT.IF ENGINE CAN BE TURNED IN THIS MANNER THEN THERE IS MOST LIKELY AN INTERNAL ENGINE FAILURE.IF IT DOES TURN OVER THEN LOOK CLOSELY AT STARTER OPERATION.
Smoke on start? Could be a valve problem where all your oil is in the bottom at start? Belts are squeaking too? Maybe a tensioner went bad?
Saw this service bulletin---
TAPPING / KNOCKING NOISE FROM ENGINE AT COLD START This bulletin amends ITB02-049. This version amends the Applied Vehicles. Please discard all paper copies of the earlier version. APPLIED VEHICLE: 2002 - 2004 Q45 (F50) 2003 - 2004 M45 (Y34) 2003 - 2004 FX45 (S50) with V8 engine. IF YOU CONFIRM: A tapping or knocking noise (similar to a piston or valvetrain noise) when starting a cold engine, NOTE: The engine is considered “cold” when it has been OFF (not running) for several hours. ACTIONS: 1. Dislodge and remove any carbon deposits that may have caused the noise and confirm that carbon deposits were the cause of the noise. • While the noise is occurring, quickly rev the engine several times to approximately 4,000 RPM. Then release the accelerator quickly, as soon as the engine reaches 4,000 RPM. • The noise should disappear immediately if carbon deposits are the cause. NOTE: • If the customer reported a noise that exactly matches the symptoms listed above, but you cannot duplicate it, the cause may still be carbon deposits. Go to step 2. • If the noise does not stop after revving the engine, or you observe any other noise that doesn’t match one described above, go back to ASIST for further diagnostic and repair information. 2. To prevent this incident from occurring again, add a bottle of Nissan In-Tank Fuel System Cleaner P/N 999MP-FSC00P to a full tank of fuel (in the vehicle’s fuel tank) according to the instructions on the label. • This product is proven to reduce carbon deposits on pistons and combustion chambers, as well as cleaning other components of the fuel system.
hi,the first thing to do is an engine flush,then refill with10/40 or 20/50 oil, semi sythetic,not forgeting to change the filter.this particular engine is quite loud but the noise should die down after about 15/20 secs if its tappy.i would also reccomend adding wynns or another oil additive to help the self adjusting tappets quiten down.An oil blockage would show up as a loud knock (big end rumble)and the oil warning light would show on the dash.
after you do the oil change rev the engine to 3000 for 30 secs.this will help to get the tappets right.
if it's a knocking sound it could be worn internal compnents ie. rod bearings. if it's a ticking sound the valves may need adjustment.
either way a mechanic will have to hear the sound to properly identify it.
these 3.3l engines are equipped with timing chains. if vehicle has prolonged down time, typically more than 4 hours, vehicle makes a chatter until the timing chain tensioners put tension on the chain. you will need them replaced.