Hollow knocking sound

[jeanbono]

Hi all,

1FZFE 200K miles. Not very stressed about it but I can hear this hollow knocking sound coming from what I think under the car (Can also hear from top but not as loud). Around the oil pan I’d say, I feel like it’s coming from the opposite side to the exhaust pipes but its hard to tell, the sound is not super localised. It gets much louder on an incline with the front wheels lower than the rear wheels and that’s the only time I noticed it when walking out with the engine running that way, so might not be a new thing. I feel like it even stops when front wheels are higher. And when flat it’s there but not as loud, which explains why I never really heard it when checking fluids on a flat surface maybe. Things to note:

-I have an exhaust leak somewhere (a mechanic told me as a FYI, have not looked into it yet). I was thinking it could be related, some sort of resonance?

-Oil sump is full and engine works great/oil lools great.

-Cant see anything hitting anything

Video of the sound. I filmed under the fan but I think its louder around oil sump.

 

[jeanbono]

To be honest can also hear it from the top. It just does not sound as loud on the video because the sound of the engine is taking over.

 

[petegangies]

check all your pulleys

 

[jeanbono]

thanks mate, all pulleys look good. Im blaming exhaust resonance due to my exhaust leak maybe

 

[60 toy ota]

Without being able to watch the videos I say check your exhaust hangers. Could also be the cause for the exhaust leak

 

[petegangies]

You'll have I think 4 rubber exhaust mounts. They split across the centre and your exhaust can have excessive movement which can cause leaks. Definitely sort an exhaust leak out, car will run better and sound better. Use a long piece of clear plastic tubing as a stethoscope to pinpoint the source of the noise, you can also run it around the exhaust flanges to listen for leaks. The thinner harder hose that fits in your ear tends to work better for this as they're quite rigid compared to rubber vacuum hose, so the sound travels better. Cut it down to anywhere up to a meter long, and it will still work quite well.