I have a 2004 Nissan Quest. When I start the car, a loud knocking noise can be heard from engine. As car warms up, the noise decreases. When accelerating you just hear a faint knocking noise. Dealer says it’s the timing chain. I thought with timing chain the noise should get louder, especially when accelerating. Could it be something else?
Since it retreats with temperature it could be a couple of things, I guess. If anything, I would expect a timing chain to get louder. That’s under the assumption that there’s some hydraulic chain tensioner.
Normally this would point to some fouled oil passage. As the oil warms the offending fouled passage gets the proper (or increased) lubrication.
I’d recommend an Auto-Rx treatment just to rule out some oil related issue (www.auto-rx). Very simple to use.
I don’t know much about “auto-rx”, but I think any kind of additive is going to be useless here. This forum is filled with discussions that pretty much agree that engine oil additives do more harm than good except for very specific problems, and even then only as a ‘band-aid’ solution.
Can you describe where the noise seems to be coming from? Front of engine? Bottom of engine? Does it seem to be knocking with every revolution of the engine or at half that speed, or something else? Does it speed up and slow down right in time with engine RPM? Was the engine run low on oil or overheated? Did this start gradually or just appear one day? What kind of oil do you use in the engine?
The engine noise is coming from the back of the engine where the timing chain is located. The knocking occurs with every revolution of the engine. As the engine warms up the knocking noise decreases and at high RPM you don’t hear it much. The noise started to appear gradually after about 60K miles. Mainly during the starting of the car. If the car is warmed up and you turn the car off and turn it on again you don’t hear that much noise. If the car is turned off for a while and turned on again you hear it. I’m not sure what kind of oil is in the car. The last oil change was done by the dealer.