Hi !

 

Do you know what this is???

 

There's a noise coming from the o/s of the engine bay, around where the boost pressure sensor and brake booster is. It's a kind of air leaking or motor warnout noise...

 

There appears to be no pipes loose, the first thing that sprung to mind was the re-circulation control etc, but as I get the honk I don't think it's that. It only appears to do it on idle or neg boost, I think It's always been there, but now you can hear it in the car with the door closed. The noise runs on after the engine has turned off...

 

http://jezzer.no-ip.com/300zx/jezcarnoise_sm.avi

The WAV file has two samples with the engine running & stopping

 

1. With the door open you can hear it very clearly around the door hinges!

 

2. Inside the engine bay near the brake booster etc.

 

Jez.

Jez, it sounds like one of the vacuum tanks of the clutch is leaking

 

try disconnecting this hose (block of the piece that comes from the plenum) and listen if you still get the sound.

 

 

if the sound is gone, then it's probably the tank that's in the fender.

To get to it you'll have to remove the plastic shield in the wheel well

 

-Eric

Thanks Eric,

 

Yes, it's that plastic expansion box, I'll have to get a second hand one!

 

See ya,

 

Jez.

Okay dokie...

 

Finally, I pulled out the expansion tank again and stuck it on the end of a long hose to make sure where the noise is coming from.

 

Whether a good or bad thing to do, I pressurised it to 20psi and there were no leaks. (with a foot pump!)

 

I sealed the gasket edge with some special "hard as rock" sealent, it's very very sealed on that edge now, believe me.... and it still makes the noise.

 

So I can determin either...

 

* Some other leak in the system is causing this box to make an air circulating noise?

 

* It has something inside causing it to only leak on vacume, not when pressurised (which I tested). Therefore there must be some hair line crack I can't find?

 

It only makes the noise with the clutch engaged, it's quiet with it dis-engaged (the clutch pedal down)

 

Anyhow... How much of a pain is it to get to the other clutch expansion tank in the engine bay? I may check that out next?

 

Ideas?

 

Jez.

it could also be the brake servo unit leaking air

test it by turning engine off and see if foot pedal is rock solid straight away or does it take several pumps on pedal to empty servo of air . if it takes several pumps to get rock hard(lol) after turning engine off then its ok

Richard