Chirping noise rear of bank 2
Thread Starter
Senior Member
Joined: Jan 2023
Posts: 355
Likes: 279
From: Gulf Coast
2014 Mercedes-Benz E350
Chirping noise rear of bank 2
I noticed a chirping from under hood, first thought was idler pulley, or tensioner. Nope, coming from back of engine. using mechanics stethoscope, just the tube, loudest under left rear of intake plenum. There is a valve assay on left side of intake plenum, the noise is loudest poking hose from behind intake just to nether right of this valve directly above head below intake plenum but center wise of head. It echos well off firewall. Not as loud moving toward vacuum pump area, moving closer to the plenum valve.
I'll try to get pictures and/or a video if it cools down today.
I'll try to get pictures and/or a video if it cools down today.
Thread Starter
Senior Member
Joined: Jan 2023
Posts: 355
Likes: 279
From: Gulf Coast
2014 Mercedes-Benz E350
I thought it might be vacuum pump, but scanner shows nominal readings, then I thought PCV, but removing oil cap did nothing. I'm leaning to the vacuum pump still, it's quiet when cold, after warms up chirp is non stop.
Thread Starter
Senior Member
Joined: Jan 2023
Posts: 355
Likes: 279
From: Gulf Coast
2014 Mercedes-Benz E350
I noticed a chirping from under hood, first thought was idler pulley, or tensioner. Nope, coming from back of engine. using mechanics stethoscope, just the tube, loudest under left rear of intake plenum. There is a valve assay on left side of intake plenum, the noise is loudest poking hose from behind intake just to nether right of this valve directly above head below intake plenum but center wise of head. It echos well off firewall. Not as loud moving toward vacuum pump area, moving closer to the plenum valve.
I'll try to get pictures and/or a video if it cools down today.
I'll try to get pictures and/or a video if it cools down today.
Thread Starter
Senior Member
Joined: Jan 2023
Posts: 355
Likes: 279
From: Gulf Coast
2014 Mercedes-Benz E350
It is in that context, but if you close the hood, you barely hear it, and get in the car it's gone.
Now mine is not that bad, but at cold start, and it is quiet till fully warmed up.
Again, while similar, not the same because I take off my oil cap and mine continues. But the tone of it is the same. Just like a belt chirp. why I'm thinking vacuum pump, or intake seals, as my Spark plugs and left cam sensors were just recently done.
My belt is new.
Now mine is not that bad, but at cold start, and it is quiet till fully warmed up.
Again, while similar, not the same because I take off my oil cap and mine continues. But the tone of it is the same. Just like a belt chirp. why I'm thinking vacuum pump, or intake seals, as my Spark plugs and left cam sensors were just recently done.
My belt is new.
Super Member
Joined: Aug 2004
Posts: 954
Likes: 245
E550 Coupe 2wd (2016)
If it sounds that similar then I'd assume it's the same problem. I don't know what exactly makes the noise in the vid but it may be that yours just happens to make the sound with the cap off.
I've never heard a PVC system make any noise even remotely close to that, but clearly something is causing it. I'd block off the PVC hose to the intake and see if it goes away, then you'd know for sure. You can pop the hose off near the throttle body. I have a pix of it somewhere because I popped that line off to add a catch can because my intake was dripping wet with oil. Apparently that's normal, so something else to think about
I've never heard a PVC system make any noise even remotely close to that, but clearly something is causing it. I'd block off the PVC hose to the intake and see if it goes away, then you'd know for sure. You can pop the hose off near the throttle body. I have a pix of it somewhere because I popped that line off to add a catch can because my intake was dripping wet with oil. Apparently that's normal, so something else to think about
Thread Starter
Senior Member
Joined: Jan 2023
Posts: 355
Likes: 279
From: Gulf Coast
2014 Mercedes-Benz E350
That's a good experiment. I'd thought of taking throttle body off and use my smoker to check for leaks, but both experiments must be done fully warmed up.
Trending Topics
MB World Stories
The Best of Mercedes & AMG
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
Thread Starter
Senior Member
Joined: Jan 2023
Posts: 355
Likes: 279
From: Gulf Coast
2014 Mercedes-Benz E350
I noticed a chirping from under hood, first thought was idler pulley, or tensioner. Nope, coming from back of engine. using mechanics stethoscope, just the tube, loudest under left rear of intake plenum. There is a valve assay on left side of intake plenum, the noise is loudest poking hose from behind intake just to nether right of this valve directly above head below intake plenum but center wise of head. It echos well off firewall. Not as loud moving toward vacuum pump area, moving closer to the plenum valve.
I'll try to get pictures and/or a video if it cools down today.
I'll try to get pictures and/or a video if it cools down today.
Actually was found by a friend, completely by accident, unplugged it to get to another part and just happened to catch it in the corner of his eye. It actually looked like it was nicked by a sharp blade not split due to age or heat cycles, probably why it was able to make the high pitched chipping sound.
Problem solved,
Super Member
Joined: Aug 2004
Posts: 954
Likes: 245
E550 Coupe 2wd (2016)
Interesting. I still can't wrap my head around how it makes that sound.
In the comments of the vid a guy says: "The noise you're hearing is air passing through the front crank seal due to high vacuum. Pop the diaphragm cover off the vent valve, remove the diaphragm and spring, cannibalize the same parts off a new valve assembly and reassemble."
I dunno, guess I have to take his word for it since I never opened that thing up. I'm also assuming he's taking about where the air for the PCV enters the valve cover? From what I remember it's a cast Alum piece that looks like part of the valve cover? To me "crank seal" is something else. No, not a condom, but the parachute oil seal on the crankshaft, which would not make any sound. I figured there was simply some baffles under that cover to keep oil from exiting, but clearly it's more complex.
So that mystery crack/split/cut in your tube; we're talking about the hard plastic ~1/2" OD tube that connects between the eng and brake booster? I'm trying to figure how that leak could make noise? If it's the "front crank seal" then a leak on that tube would mean less air is passing through said seal so it should not make noise. Uggg...
Well, glad you found it so quick or you'd likely be chasing that ghost for a while.
In the comments of the vid a guy says: "The noise you're hearing is air passing through the front crank seal due to high vacuum. Pop the diaphragm cover off the vent valve, remove the diaphragm and spring, cannibalize the same parts off a new valve assembly and reassemble."
I dunno, guess I have to take his word for it since I never opened that thing up. I'm also assuming he's taking about where the air for the PCV enters the valve cover? From what I remember it's a cast Alum piece that looks like part of the valve cover? To me "crank seal" is something else. No, not a condom, but the parachute oil seal on the crankshaft, which would not make any sound. I figured there was simply some baffles under that cover to keep oil from exiting, but clearly it's more complex.
So that mystery crack/split/cut in your tube; we're talking about the hard plastic ~1/2" OD tube that connects between the eng and brake booster? I'm trying to figure how that leak could make noise? If it's the "front crank seal" then a leak on that tube would mean less air is passing through said seal so it should not make noise. Uggg...
Well, glad you found it so quick or you'd likely be chasing that ghost for a while.
Thread Starter
Senior Member
Joined: Jan 2023
Posts: 355
Likes: 279
From: Gulf Coast
2014 Mercedes-Benz E350
Ignore the comments from the video, I was only using it to display a similar sound to mine, not the actual problem in it. He also stated, remove oil cap and noise stops, as I stated previously, mine did not do that either. So, sorry if I misled, was far from my intentions.
We are not talking about a hard plastic tube, we are talking about a 3/16" soft rubber vacuum line attached to the back of the intake plenum above the vacuum pump that somehow got a small cut just big enough to produce a noise akin to letting air very slowly escape a balloon making a high pitched squeal. Again, sorry if I led you down the wrong path.
Where did the front crank seal inter the conversation? You lost me, there.
The noise was highly localized exactly where I had previously stated, not much else there but a stethoscope helped pinpoint the location, once the line in question was moved for better observation as the sound was from a cut on the bottom of line so sound bounced off top of valve cover, noise changed pitch and was easy to see where it originated.
I spent my life chasing noises in customers cars, if a fairly accurate description and when is given, I can find it. Very rare that I've not.
I know I'm getting old, and my communication skills have faded, I thought I gave a clear description. So my apologies for any misunderstanding.
We are not talking about a hard plastic tube, we are talking about a 3/16" soft rubber vacuum line attached to the back of the intake plenum above the vacuum pump that somehow got a small cut just big enough to produce a noise akin to letting air very slowly escape a balloon making a high pitched squeal. Again, sorry if I led you down the wrong path.
Where did the front crank seal inter the conversation? You lost me, there.
The noise was highly localized exactly where I had previously stated, not much else there but a stethoscope helped pinpoint the location, once the line in question was moved for better observation as the sound was from a cut on the bottom of line so sound bounced off top of valve cover, noise changed pitch and was easy to see where it originated.
I spent my life chasing noises in customers cars, if a fairly accurate description and when is given, I can find it. Very rare that I've not.
I know I'm getting old, and my communication skills have faded, I thought I gave a clear description. So my apologies for any misunderstanding.
