Breather valve (A0004762232) making whizzling noise
Hello!
Would anyone have an idea what is going on with my G? I have 1991 300GE.
I have tried to search the net for answer, but it seems I'm the only one having this issue?
The breather valve (A0004762232, below right hand rear side window, behind paneling. Also includes safety check-valve so that fuel is not leaking out in case of capsize) is making really irritating whizzling sound.
I thought it is faulty valve, and replaced it with a new one. But the whizzling is still there. I don't know why it is making this sound.
I understand that this valve is sucking fumes out of fuel tank to KE Jetronic (vacuum while car is running). Sound does not appear at idling, but immediately when RPM rises. And with higher rpm it stops. But at normal driving speeds of 10-100 km/h it is there, buzzing away. And you can hear it inside. And it is the valve making the sound, not hoses etc. I tried to blow into it, and it starts buzzing. Both new and old.
So what could cause the sound? Is there too strong flow through valve (too strong vacuum?) or something like that. When you blow through valve moderately, only sound is the flow of air, but with harder blow buzzing starts.
Picture Valve1: Here is the breather valve setup (valve is No 35).
Picture Valve2: Here is the breather valve connection to charcoal filter and further to KE Jetronic
Thank you for any help!
-Harry
Hello Harry,
The noisy breather valve can be a problem. I have replaced one for a new one and the valve was still noisy. I suspect the problem could be the fuel filler cap. The cap is supposed to be breathable as well, where the breather hole is; I do not know, I suggest firstly to remove the cap and see if the noise is present under that condition in which case you need to blow out the fuel cap's breather hole where ever that is.
I have sprayed some lubricant in the valve and the noise did not go away or it would return.
Or turn your Radio volume up a little. 
Hello,
Here are some videos for you so you know what kind of torture I'm talking about 
Of course when paneling is on, the sound coming in the cabin is damped quite lot, but still that whizzling is audible...
So I "fixed" the problem temporarily the following way: I just taped the suction pipe with plastic tape, and pinholed it from centre to create kind of orifice plate to reduce the suction. Now there is no noise, but I guess no actual suction either. This is at least silent until I figure out better way to deal with the valve...
valve noise 1 small - this is how it was. So any rpm over idling causes the sound.
valve noise 1 small - YouTube
Valve noise 2 small - suction noise without valve
valve noise 2 small - YouTube
picture: suction pipe orifice.
valve noise 4 small - "fixed" noise. so no noise.
valve noise 4 small - YouTube
Attached Thumbnails
Hi, yeah that would be very annoying! Without knowing exactly how that system is plumbed, it's hard to know where the pipes come from/go to, but could it be a blocked pipe beyond the valve? On your original post, it shows a looped pipe, does that go beyond the valve and to a higher point and what is item 29? Maybe blocked? If removing the cap makes no difference, then that indicates that the suction or pressure is coming from somewhere else not the tank. Do you have a diagram of the entire venting/fuel supply/return system?
I know on diesel 460's, (at least mine, a 250GD) there is a valve in the side as well, that joins to a pipe (breather) which goes down the right quarter panel, then along inside the bottom of the rear door/floor frame and exits about half away along, if that pipe was blocked, the tank would have to breath through the valve, which I don't think is it's primary function.
I'd check all pipes into/out of the valve are free.
Hello,
I don't have the whole system on one diagram.
Here is a pic of fuel lines. So from tank comes line to first fuel pump, then to second pump, and from there to fuel distributor/injector. Return line runs from there back to tank.
And as seen in fume diagram, also the valve suction line ends up to fuel distributor/injector, via active charcoal filter.
This line is open, there is large amount of air being sucked (video, where line is disconnected, valve noise 2).
So basically as I understand it goes like this:
- Hose from bottom of the valve is coming directly from fuel tank (=the fumes to be sucked away), so hose number 20, 14, 10 etc
- Hose from fuel injector (creates vacuum while car is running) comes to the side of the valve. hose number 31 going to injector
- top of the valve is replacement air hose? If the breather hose is blocked (20 etc), suction will go via this one (hose 23 to 31). Or if there is a vacuum in the tank, it gets replacement air via this connection (so flow from 23 --> 20) (after hot day the tank has warm gasoline in it, and fumes have been extracted from the tank via fuel cap/this valve. during the night gasoline cools, and there is negative pressure in the tank, and replacement air is needed). The hose number 23 is just a 5 cm long bend of hose, so nothing goes into the valve.
At least this is how this valve seems to be working. from bottom of the valve overpressure (blowing in) goes to suction connection (hose number 31). You can freely suck replacement air from bottom of the valve, and it comes via top connection (so hose number 23).
Ok, maybe check hoses 25 and line to tank are intact/free
Hello,
Actually there is only line 23, no 25 at all. I suppose dirrerent models/engines have 23 and others 25.
I can't see how that hose would be a problem.
But I fully agree it has to be the breather line to tank. Some of them has to be leaking...
that would create situation, where flow through the valve is too strong, and then it starts whizzling. At least that sounds feasible. I mean the tank has to be tight, so not leaking gasoline in any position. This means that when the valve is working properly, there should not be any flow through it (it sucks fumes out of tank, but after a few secs there is slight vacuum in the tank, so flow is 0 after that --> no whizzling). Now if suction line from tank is leaking, there is a flow always. And noise.
I have to dig in there when I have time (and when it wouldn't be freezing out). After all, there are a few hoses to be checked, and it is tight space around the fuel tank. Possible leaks are at hoses 20,14,10,8,18,12 or 5. Might not even be possible to check the lines without removing the fuel tank....
Now when I'm checking it, actually where does the number 5 go...? Have to try to find out...
Harry
Do you have the chassis number / VIN that you could post / PM / email me so i can see what set up the truck is running and maybe get some proper diagrams?
Gav
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Hello Pistonhead,
Unfortunately I already have tried opening the fuel cap. Does not have any impact.
When I first time removed the valve to inspect it, it actually got pretty silent (opened it and basically just played around to see if it is ok), but only for a day or so. Then the buzzing returned, and I figured what a heck, I'll get a new one.
Seems weird that merc would put the bugger inside the car, if there is tendency to start making noise. There would be space for it outside also, where it could whizzle as much as it likes without bothering anyone.
Have been already thinking of bypassing the whole valve, as you said, the cap is also breathing, so there will not be pressure building up in the tank. Or bypassing just the valve with piece of hose. Then the only problem is capsizing the car as far as I can see. Then the fuel runs to engine bay via hosing.
The sound is just so irritating and high pitched - like your own personal vuvuzela - that I'd rather get rid off it.