I have this noise which sounds like it's coming from the dashboard. I've already had the dash off and felted all the plastic tubes but that didn't make a differnce. I should of drove around with the dash off last time and it's probably my next step but has anyone ever dealt with this type of noise before? I used a stethoscope to narrow down the noise and for the only place I can hear anything is on the firewall. Looked at pictures of the heater box to see if it' mounted on there but it isn't. Thought it was the heater box too but that thing is drenched in silicone lube and no difference.

 

It may be worth a check on the engine bay side of the firewall, to make sure nothing is loose and tapping the firewall, or being transmitted in via a heater pipe or something.

 

Yeah tried that too had wife drive around with me on top of the engine bay. Had the winshield cowl off and you can near the noise coming from the heater box intake. Used the stethoscope on the outside and it was still on the firewall.

 

And there's no video of that?? Have to say I feel really let down right now.

 

Now that's a seriously dedicated investigation.

 

I've sold cars for less. I get your aversion to rattles.

 

There are many different types of noises. If you could record it and post or at least describe it we'd might be able to help better?