I have noticed over the last few months an audible "rattle" at startup. it only lasts a second (or less) but it is clearly there. Once oil pressure is up, it goes away. You never hear it any other time. I have not had the car a year. It has 75k on the clock. I am running Mobil1 40w with a WIX oil filter. What causes this?

 

are you 6mt? i occasionally get a rattle on cold starts. the rattle is from the counter-balance shaft in the tranny though. it's been checked out by the dealer and it is "normal".

 

This is actually an automatic car. The rattle sounds like it's enginet top-side and isnt getting oil. some early Toyotas 4cyls were notorious for this as the oil filter was mounted upside down and after sitting would drain back down into the engine. This "void" caused the same type rattle on startup until the oil filter filled with oil. Not a possibility on our cars as they mount right side up but the symptoms are similar.

 

Mine does it on very cold mornings for about 2-3 seconds. My theories are: 1) run standard 10w-30 oil, the 40w may be to thick at the start to lube the top end. Some people use Lucas oil stabilizer. These may decrease the rattle some; 2) it could also be your timing chain (not likely based on your description). I'm not sure, but it might use oil pressure to adjust the tension guide, which in turns stops the rattles. There isn't much oil pressure at the start and if your oil is 40w, it may be slightly starving at the outset, and; 3) not likely, but it is very slightly possible that it could be the oil pick up in the sump blocked up a bit.

If its only happening at start up then its not much of a problem, however if it rattles as you drive or it rattles constantly, your chain might be worn or the guides chewed up (I believe it may have guides) or something as simple as the "oil pressure regulator valve.

Like I said, these are mere theories, I'm not an expert on the G, but others on the site certainly know much more.

 

fwiw, I am experiencing this same problem and understand this to be valve training chatter. Mine does this as well when the motor is cold. If ambient temp is down then it will be more pronounced. This only lasts a split second then the motor runs quite well. It is irritating cause its an atrocious noise and makes you think your engine is f'ed.

I picked up an Infiniti Oil filter and installed it. For a few days I did not get the noise, but it came back eventually. Not sure if I got a bunk oil filter with check valve or what. Ahh well, tommorrow I am going to change the oil cause its time and install another dealer filter and see what happens. Possibly inspect the old one if Im feeling motivated.

Edit - I am running 5w-30 Castrol.

 

What causes this is an oil that is too thick at cold engine start ups and isn't flowing quickly to lubricate engine parts. The rattle noise you are hearing is metal-to-metal wear, which is taking a substantial amount of mileage off of your engine. The cure is to use a better flowing oil in the cold, i.e. a 0W-30 or 5W-30, good performing synthetic oil. Change the oil over to the better viscosity and I think you will find the cold engine start rattle noise gone.
Good luck with it.

 

I'm with Braintree on this. I had a 95 Maxima for 10 years or so and the rattle from the timing chain was obvious. It's a common thing with the VQ30 engine if you check the forums. I'd bet the VQ35 may have the same behavior. Oil pressure forcing a piston to move the chain tensioner to tighten the chain may get inadaquate oil pressure at startup to tighten the chain enough. The slack side of the chain then contacts the housing creating the rattling sounds. The startup rattle on my Max eventually went away. It was never a problem beyond the noise. If it doesn't go away as it warms up, then I'd be concerned. Make sure what the noise actually is before ignoring it though.

 

There is a sprocket TSB - search for those keywords.

 

40w oil?

How do you say D'oh on Japanese?

Start by using the recommended oil- 5w 30.

 

Just experienced this for the first time today -- ungodly rattle/grinding noise on startup, scared the bejeesus outta me. Then the car runs fine. Running Amsoil 5w30 and Wix filter, though I don't think it's an oil-related issue. Sounds to me a bit like the starter fails to disengage.

 

Another auto driver had this problem. Turns out the bearings went bad and metal shavings were all over the place. So Infiniti gave him a new motor.

This noise only happened on cold start and was random.

 

^^ How about a link to that thread?

Anyone else? Just tried it again, happens on first start, but not second or third. Listened closely with the hood up and it really sounds to be like the starter is not disengaging. Oil level is fine.

 

^

https://g35driver.com/forums/engine-...upe-video.html

There is a video and copy of the invoice included in that link.

People were "guessing" that it could be the ABS self test, timing chain, etc etc.. Turned out the motor the fuked. And the dealship only found about it on accident when they had to replace the valve cover seal. And noticed the metal shavings.

 

Thanks, JJ, guess I'll drop the pan for a looksee.

 

I have been using 0-40 mobil 1. this oil is supposed to last at least 7500miles or 6 mths or some **** like that. well I think I only went about 3500 miles but didn't change the oil for about 7-8mths. that is when I got the rattle. your oil is too thin or the outside temps are too hot. I switched to 10-30 full synthetic and the rattle stopped immediately.