I am getting this metallic grinding noise on cold start ups. It will grind for a few seconds on cold start ups, then stop. I replaced the pulleys, belt, and tensioner so I don't think it's that. What do you guys think it is? 08 Infiniti G35x.

LINK: https://www.youtube.com/watch?v=Dn5J...ature=youtu.be

 

If you turn it off and turn it back on does it do it again? Does it happen only on a cold start? I’d say yes it is the starter. Sounds like the overrunning clutch in starter is bad.

 

If I turn it off, then back on while the car is still cold, It does it again for like half a second. But if I go out for a drive and the car is warm, it won’t make the grinding noise. Dang, that’s what I was afraid off. Looks easy to remove on RWD Gs, but AWD Gs are much more of a pain in the ***, atleast from what I have read online.

 

Changed the starter, still getting this grinding noise. I also started the car briefly without the serpentine belt on, and it still made the same grinding noise. Any ideas?

 

Check the pulleys

 

Hi, I replaced the idler pulleys, belt and tensioner. Also by starting it without the belt on any of the pulleys, and still getting the noise, wouldn't that eliminate any pulleys being the source of the noise?

 

Removing the belt was a good test!

We now know the sound is not from the a/c compressor, alternator, power steering pump or the starter.
I don't think the engine could make this sound... so that leads me to think the transmission. It does sound a little like a "hydraulic" type sound.

I don't think there is an automatic transmission dipstick on your car, so you can't easily check the fluid level.
Maybe take it to a shop and get the transmission fluid changed...

Other than that, I am stumped!

 

So the 07-08s actually do have a dipstick; I checked it and the fluid was at the right level and was still cherry red. I did a drain and refill to see if that did anything, but it still makes the noise. Do you think this can be some sort of exhaust leak? Since the noise only happens once I first start the car, I can't drive it to a shop since it make the noise once its there. It is more prominent on colder days, as today was rainy and cold compared to yesterday, and the noise lasted longer today.

 

Next time it makes that noise, try blipping the throttle slightly to see if the frequency of the noise changes with engine RPM's.

 

after listening to this video I would have to say it’s more of a whine sound then a grind sound. Now that you’ve eliminated all rotating components on the front of the engine, it sounds like your transmission fluid pump. My 07 sedan’s trans pump intermittently would whine on hard acceleration, then out of no where it literally sounded like a pulley bearing took a crap and I got left stranded in the middle of the country! I would definitely stick a stethoscope on the trans right at the bell housing mating point. If your really feeling froggy, unbolt the torque converter from the flex plate, push the converter back about 3mm and start it up see if that sound is gone! Good luck!

 

Oh man, I hopes its not the tranny.. mines already been rebuilt. Warranty ended a couple thousand miles ago..

 

Did you check main drive pulley

 

Sounds like a likely coincidence! Of course after it’s been rebuilt. Do you have a list of what was replaced? I bet the pump wasn’t touched.

 

Thanks to your comment, I diagnosed the problem as the tranny filter. Because of Covid-19, I decided to do it myself. I dropped the tranny pan and changed the transmission filter after watching youtube videos and following a DIY thread on G35Driver. The shop I had rebuild it told me to bring it in after 24k miles to drop the pan and change the filter, but I honestly thought they was trying to get squeeze more money out of me. From what I see online, people say that the filter isn't serviceable since its just a screen. However, my filter was indeed clogged up and I assume was hindering the ability to suck up the fluid in the pan. No more whining noise!