- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
The AC clutches go on those cars, if you can get the car in the air while its on you can use a long screw driver to touch the tip of the screw driver to the compressor housing and the handle end and cover your other ear with your hand. The noise should be somewhat close to what you hear while the car is running be aware of bad tensioner also making a knocking noise when they go bad due to the internal spring assembly.
you hear connecting rod noise or crankshaft knock due to worn main bearings.dont buy that vechicle engine is shot.any time you hear engine knocking it needs overhauling or replaced fix a engine to remove engine and replace with new or rebuild engine.you will be out of $2500 to $3000 go look for another vechicle.knocking engine wont last a month.cant go far distant engine oil pressure will drop down until engine lock up.
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.
A failing AC compressor clutch will make noise more like a rattle but it will become hot enough when it is failing that the rubber grommets around the clutch plate will begin to "stink" as they begin to melt and fall out. It will smell like burnt rubber smoke.
If you remove the drive belt you can try to see if there is play in the pulley for the AC compressor but you won't be able to "engage" the clutch to test it (uses electrical switching). If you can spin the pulley and it makes noise, suspect a failing compressor clutch.
While you have the drive belt off spin the water pump pulley and you should only hear a gurgling noise from water in the motor being pushed and no metal on metal noise whatsoever. If you hear a clunking noise when the motor runs you could also have a worn motor mount so you would want to check those also.
Here's what you don't want to hear...A loud knocking noise from inside your engine is generally caused by a crank or rod bearing...when caught very early, sometimes they can be replaced. however, once the noise is loud, the attending crankshaft journal gets "hammered" out of shape and the job becomes very expensive and in most cases more costly than engine replacement. There is one other item that can cause a loud knock...your flywheel. Bearing problems generally cause low oil pressure. If you have that, it's gone...if not, have the flywheel checked before sending the engine to the scrapyard.
try having someone kill the a/c while you check for the noise. if it stops then check further into the compressor where you said you thought it was coming from. It could be the bearings in the compressor clutch going out.