Hi all,
here is the thing: I saw a lovely Z4 3.0, M54 engine, 100 k miles and 9 owners, but with full history. The last owner was a gentleman that kept the car pampered for 1-year fixing some aesthetical things. I'm almost ready to conclude the deal (I'm waiting for the guy to get the car MOTed), but there is something that is concerning me.
Basically, with the car parked in neutral, or with the clutch pressed, tapping the accelerator, or accelerating let's say at 2-3000 rpm and then lifting the pedal, I could hear a single metal knock coming from the engine. It seemed localized in the bottom middle.
The knock was a single one, so nothing like rod knocks that change "tempo" with the rpm and it was happening every time the accelerator was lifted. Stupidly, I didn't record a video and I didn't find anything similar online. I was audible only with the bonnet open I think (didn't notice anything during normal driving, but maybe now I would).
I tried to keep the car at 2000, and 3000 rpm to see if it was starting to rattle from the VANOS, but in that case, there was no noise.
I then moved on to checking other things on the car since I was really excited, so I forgot about it. However, tonight I couldn't stop thinking about it
Do you have any idea of what it could be, or for what test could I do when I will go there again? At least something that would allow me to exclude catastrophic failures in the near future.
Any advice is appreciated.
Cheers,
Stefano
here is the thing: I saw a lovely Z4 3.0, M54 engine, 100 k miles and 9 owners, but with full history. The last owner was a gentleman that kept the car pampered for 1-year fixing some aesthetical things. I'm almost ready to conclude the deal (I'm waiting for the guy to get the car MOTed), but there is something that is concerning me.
Basically, with the car parked in neutral, or with the clutch pressed, tapping the accelerator, or accelerating let's say at 2-3000 rpm and then lifting the pedal, I could hear a single metal knock coming from the engine. It seemed localized in the bottom middle.
The knock was a single one, so nothing like rod knocks that change "tempo" with the rpm and it was happening every time the accelerator was lifted. Stupidly, I didn't record a video and I didn't find anything similar online. I was audible only with the bonnet open I think (didn't notice anything during normal driving, but maybe now I would).
I tried to keep the car at 2000, and 3000 rpm to see if it was starting to rattle from the VANOS, but in that case, there was no noise.
I then moved on to checking other things on the car since I was really excited, so I forgot about it. However, tonight I couldn't stop thinking about it
Do you have any idea of what it could be, or for what test could I do when I will go there again? At least something that would allow me to exclude catastrophic failures in the near future.
Any advice is appreciated.
Cheers,
Stefano
