Strange Noise From Engine Bay When Pressurizing Intake

[Hanaldo]

Hey all,

I just wanted to quickly clarify whether this noise I am hearing is normal or not. When I pressurize the intake using an air compressor to test for leaks, I have noticed before that I get an odd whine coming from somewhere in the engine bay. I have narrowed it down to having something to do with the charcoal canister, as when that is disconnected and the lines blocked, the sound disappears. However the sound emanates from the back of the engine bay, over near the brake booster.

Now I am totally unsure why, but when I first made this discovery a few months ago I dismissed it as being normal. Upon hearing it again, I had the thought that perhaps this isn't normal and is an issue that I should rectify.

So, here is a video of pressurizing the intake with the charcoal canister disconnected. Note no noise:

Here is another video, now with the charcoal canister connected again. Note the noise that comes in at approx. 11 seconds.

I should also point out that I have never heard the sound while driving, I guess because the noise of the car covers it up or possibly the noise doesn't occur with the engine running.

Edited September 7, 2013 by Hanaldo

[89CAL]

Can you unplug the hoses from the charcoal canistor one at a time to isolate which part of the system is making the noise. Just tryong to think where the lines run. One to the throttle body on the intercooler/turbo side of the TB, one to the manifold, one to the fuel tank breather and one more? Cant remember and dont have my car handy lol

[0zhiph0p]

I'm not sure what help this is but when we pressurise air systems in trucks and trailers at work on 100 psi to release the brakes for brake adjust or whatever, the air tanks can make this sound for a minuite then the sounds goes away when they are full, it may be normal.

[GTRNUR]

The charcoal canister should only ever see vacuum as the diaphragm that opens it only gets exposed to vacuum at light throttle opening due the a valve on the cylinder 1 throttle.

I've heard that sound before, and it sounds more like throttle gasket or shaft seals.

[Hanaldo]

Well considering the noise is only there when the charcoal cannister is connected, does that not mean it must be related to it? I can pump 20+psi into the system with the canister disconnected and it will be dead silent.

Also Nur, and what do you mean cylinder 1 throttle? The engine is a 25 Neo, so there is no Cyl 1 throttle. I did think the noise might be related to a diaphragm that doesn't normally see positive pressure, HOWEVER. When I installed the Plazmaman plenum, I ran new hose for the charcoal canister so that I could run it a natural way. It now goes straight into the plenum through standard 1/4" hose. No valve anywhere. Is that likely to be a problem?

[Hanaldo]

Where is the valve supposed to be for the charcoal canister? If I have deleted that valve without knowing it, would the charcoal canister essentially be a big boost leak?

[abr33]

That is the sound of air leaking past a diaphram valve im guessing the one that only opens on vacuum being present. And sounds like a fairly small amount at that. Find the valve, and inspect. Not sure about the 34 ones but 33 is the round bit on top of canister

[Hanaldo]

Well the sound doesn't come from anywhere near the canister. Its definitely over near the brake booster.

[Hanaldo]

Does anyone know where this valve is? If it is between the canister and the plenum, then it no longer exists. I've run 1/4" hose directly from the canister to the plenum, there's no valve in that line. If it is in the line between the fuel tank and the canister, does anyone know where? I can't find a diagram anywhere.

[hardsteppa]

i do the same test from time to time, and haven't had that noise....just sounds like a leak to me. What's the pressure gauge doing, going down? After I replaced the leaking PCV valve mine holds pressure pretty well, no rapid drop or sound of leak like that. Other option would be to try getting can of party smoke and filling air compressor with it, then pressurising and seeing if any colored smoke coming out anywhere..?

[abr33]

Well the sound doesn't come from anywhere near the canister. Its definitely over near the brake booster.

the inline chechvalve on booster line? remove/block booster line and test?

[Hanaldo]

That valve is fine. The noise isn't coming from the brake booster, just some where near it. I block off the charcoal canister and it goes away, has to be something to do with that, surely?

[Hanaldo]

Right, found the bastard. The noise is coming from this. It appears to be a sensor of some sort?

[abr33]

Factory boost sensor??

[SkudR33]

Definitely the boost solenoid! Maybe the breather nipple is leaking air - it's the top one I believe

[Hanaldo]

No, that's over on the firewall. This was mounted on a bracket on the wheel arch, near where the throttle cable goes through the firewall.

[scotty nm35]

That is the solenoid for the charcoal canister, so it only sucks air from the tank when there is vac in the manifold. Perhaps it's leaking? It looks like the same part my car uses for a stock boost controller.

[Hanaldo]

Hmmm... I imagine it won't be an easy part to find I don't really want to block off the charcoal canister though. Would definitely much rather keep it.

I doubt this is the cause of my power issues anyway, it's barely leaking at all

[SkudR33]

If you send me a photo of its exact location I can get it for you! I'm friends with a wrecker who lets me fiddle through his shit

[Hanaldo]

Ah that would be awesome! I'll go take a photo now.