3.5 Nissan Engine Noise – Tapping at Cold Start UpSeptember 5, 2009 10:34 am Consumer, Drivetrain and Noises, Nissan, Service Writer, Tech/Mechanic
© DenLorsTools.com Summary: In this article we point out a common problem with Nissan automobiles equipped with the 3.5 Liter engine that causes engine tapping noises typically on cold start up. The engine has variable timing cam sprockets, three timing chains, three tensioners and three guides. Vehicles subject to similar issues may include Nissan Altima, Maxima, Murano, 350Z, Infiniti G35, G37, EX, FX, M series and QX4.
Nissan has stated before that a slight tap on cold start up that lasts for only a second is normal and acceptable. The tapping noise the vehicle in this auto repair blog had lasted much longer than that. When the car was allowed to cool down prior to starting, a tapping noise was present as long as the car was kept at idle; when the idle was raised to 1500 RPM’s he tapping would fade away. The noise when listened to with a stethoscope seemed to be coming mainly from the right bank near the firewall. This vehicle had excessive movement in the main timing chain from wear in the chain and guides. The main timing chain tensioner is pushed out to tighten the chain by engine oil pressure. The higher the RPM’s the more oil pressure is supplied. It also ratchets out like a self adjuster (similar to an adjuster for drum brakes) to maintain adjustment as wear occurs. As the chain and guides wear over time it ratchets out further and further. Once there is so much wear that it cannot extend any more, only the oil pressure from the engine pushing the tensioner, can reduce some of the excessive chain movement. That’s why at higher RPM’s the rattling subsides. Also as the engine warms up, more oil is circulated and heat expansion can help to reduce the play somewhat. The simplest way to check for excessive timing chain wear is to remove the rear access cover that will reveal the main timing chain tensioner. If the adjustment seems to be fully extended out of it’s bore – most likely the timing chain and guides have excessive wear causing the problem.
Other Possible Causes
This is not to say that the only possible cause of a rattle upon cold start up is the main timing chain and guides. The most obvious cause of this condition would simply be low oil level. Not surprising, if there’s not enough oil circulating in the engine it will make noise! Also an engine that hasn’t had regular oil changes can become sludged and oil passages, including the one that leads to the timing chain tensioner can become restricted. Also Nissan has had some problems with variable timing sprockets making noise sometimes and some tensioners that weren’t up to par. It’s important to diagnose the particular problem at hand and not assume that this is definitely the cause, but checking for a loose main timing chain is one of the most logical places to start.
The confirmed fix for the car in this article (2004 Maxima 101,000 miles) was the primary timing chain, guides and tensioner. The job normally calls for about 11 book hours which includes removing the exhaust, starter, AC compressor and upper oil pan. The repair was done without removing those components which saved a lot of time.