CryptoJoB

Hi all,

My 350z has developed a loud metal grinding noise coming from the front of the car when accelerating after stopping only after 20-30 minutes of driving. It also tends to happen more on a steep incline or a speed bump after driving for a while. Seems to have started after hitting a big pothole on the weekend, it never occurs until it is driven for a bit.

I've checked brake pads, front has plenty of tread, rear pads and rotors have just been replaced. Took it to mechanic and they diagnosed the noise as coming from the rear brakes (pads <1mm remaining), however after changing the rear pads and rotors the noise still occurs. Tyre pressure is at the correct psi. Had me and my mate jack the car up and visually inspect the underside of the car, nothing seems to be hanging, brakes and suspension look okay.

Any ideas on what might be causing this? Any suggestions would be greatly appreciated!

MicVelo

Did you take anything apart? Like hubs and wheel bearings? Possibility as they might not grind until heated up.

CryptoJoB

I haven't touched anything besides the rear brake pads and rotors. I've visually inspected the hubs and wheel bearings everything looks okay.

Aeneas137

well, you know for sure that it was caused by the pothole so something was knocked loose. it could be your 20 to 30 minute delay is just based on speed. like maybe you're not driving fast enough for the wind to interfere with whatever has come loose?

I know you said you jacked it up and took a look but did you look carefully at the cooling panel under the engine? it's that big plastic piece that directs air through the radiator and usually has to be removed to do an oil change. you could also look at the wheel well plastic liners. that or something else could be rubbing against a belt or the cooling fan.

Jack the car up again and remove both front wheels to get a better look at everything. get plenty of lighting and look carefully at everything.

CryptoJoB

I'm pretty sure that the issue is caused by heat rather than speed, on 30+ degree days it happens more frequently than on cooler days after driving around for a while. I'll remove the plastic under-tray and inspect the wheel well plastic liners and see if I can find anything. I've also noticed that when the grinding happens, I can feel the grinding happen through the accelerator pedal (shakes a little bit). Would this point towards hub or wheel bearing issue?

Aeneas137

a bad wheel bearing usually just makes noise, doesn't make a vibration through the floor like you're describing. The steering and control arm bushings would probably isolate that vibration from the wheel or pedals anyway.

If it only starts making the vibration after driving for a while then it's not something rubbing. heat related also doesn't make sense after hitting a pothole. but if that just knocks something loose then you know what does change when it gets hot? The exhaust manifolds. maybe a nut came loose.

you just need to get it jacked up or get it on a lift and take a look at everything. If you don't have the means, then take it to a shop and describe the problem and they will look into it.