weird hissing noise and diesel smell in engine compartment
Thread Starter
Member
Joined: Nov 2015
Posts: 133
Likes: 11
From: Campbell, CA (San Francisco Bay Area)
2013 GLK250, 2022 Tesla MYLR, 1997 Correct Craft Ski Nautique
weird hissing noise and diesel smell in engine compartment
We've started hearing a hissing sound, and we've been smelling diesel from the engine compartment. I thought it might be a blown intercooler hose based on the sound (but that wouldn't explain the smell, plus no error codes). I took all the bottom covers off looking for a hole or lose fitting on the exhaust lines, but nothing. The hissing is most noticable as RPMs drop although when driving, I hear it when accelerating as well as slowing down. It almost sounds like a sucking sound, but since there is diesel fumes, I think it is pressure instead.
Started the car with the top cover off, and rather than hearing the hissing on the right side where the exhaust manifold, etc. is, the hissing sound is coming from the left side. Here's a youtube video I did of it. You can kind of hear it when RPMs go up, but definitely as the RPMs drop. In addition, when the engine is shut off, there are some additional weird noises that seem to be coming from the same area. I can't tell where it is coming from. If anyone has any ideas, it would be greatly appreciated.
Thanks.
Started the car with the top cover off, and rather than hearing the hissing on the right side where the exhaust manifold, etc. is, the hissing sound is coming from the left side. Here's a youtube video I did of it. You can kind of hear it when RPMs go up, but definitely as the RPMs drop. In addition, when the engine is shut off, there are some additional weird noises that seem to be coming from the same area. I can't tell where it is coming from. If anyone has any ideas, it would be greatly appreciated.
Thanks.
MBWorld Fanatic!
Joined: Sep 2015
Posts: 2,584
Likes: 343
2013 glk 350
I’ve heard about Dyes for finding leaks in diesel, gasoline , cooling systems, etc that you pour into the fuel and use an infrared or ultraviolet light to trace leaks . Kits can be very cheap with light included. Amazon or your local auto store probably has these .
MBWorld Fanatic!
Joined: Jun 2021
Posts: 1,010
Likes: 281
From: South Texas
2014 GLK350 base model (active) ; 2001 E320 base (retired); 2001 Wrangler soft-top
MBWorld Fanatic!
Joined: Jul 2012
Posts: 1,369
Likes: 319
From: WI
GLK 250
Can't see any vid, but off the top of my head, I'm thinking fuel filter area. Any recent service done? If so, what?
Any wetness or dampness around any of the 4 fuel injectors? Look for shiny/oily residue, as the smell itself may blanket the entire local area under the engine cover.
Any wetness or dampness around any of the 4 fuel injectors? Look for shiny/oily residue, as the smell itself may blanket the entire local area under the engine cover.
Trending Topics
Newbie
Joined: Oct 2022
Posts: 10
Likes: 3
S / Cayenne / GLS
Mine is a turbine, I directly remove the front, it is conducive to heat dissipation, as for being able to smell the odor, I recommend cleaning the engine, there should be none. I smelled it when the oil was dissipating heat and leaking oil before, and then it was no longer after it was done
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
Member
Joined: Nov 2015
Posts: 133
Likes: 11
From: Campbell, CA (San Francisco Bay Area)
2013 GLK250, 2022 Tesla MYLR, 1997 Correct Craft Ski Nautique
Can't see any vid, but off the top of my head, I'm thinking fuel filter area. Any recent service done? If so, what?
Any wetness or dampness around any of the 4 fuel injectors? Look for shiny/oily residue, as the smell itself may blanket the entire local area under the engine cover.
Any wetness or dampness around any of the 4 fuel injectors? Look for shiny/oily residue, as the smell itself may blanket the entire local area under the engine cover.
It's probably hard to hear in the video but it almost sounds like a sucking sound (although that wouldn't explain the diesel fumes, so it could be something leaking out). I suspect if someone recorded the same video of the same engine without the noice and then compared the, it would be pretty obvious. Does anyone have any pictures or diagram of what all of the components, etc. are for our engine so I can work through each one?
Also, does anyone know if there is a mechanical linkage to manually give it throttle from inside the engine compartment like you can do on a gas car with the throttle plate? Or is it all electronic? I'd like to be able to rev it myself with a stethoscope rather than having my wife rev it from inside the passenger compartment.
Here's the link again (will have to be 'corrected' and pasted): http(ESS)://youtu.be/IigS-DXlR0I. (remove '(ESS)' and replace with 's')
Thanks.
MBWorld Fanatic!
Joined: Jun 2021
Posts: 1,919
Likes: 522
From: New Hampsha
'17 GLS450, '14 GLK250, Grandpa's Roadster
MBWorld Fanatic!
Joined: Jun 2021
Posts: 1,010
Likes: 281
From: South Texas
2014 GLK350 base model (active) ; 2001 E320 base (retired); 2001 Wrangler soft-top
EDIT : the video is in this reply, at end
.
.
Obsolutely EVERY person who has responded in here, cannot see a link or embedded video. You probably have it successfully posted in another forum, which is prob the folks who can see it 
And now, you want folks to edit your malformed URL? Asking a lot
Here, let me give it a try (BTW - software engineer here with 35+ years experience)
.
.
.
.
And now, you want folks to edit your malformed URL? Asking a lot
Here, let me give it a try (BTW - software engineer here with 35+ years experience)
.
Last edited by calder-cay; Mar 7, 2023 at 01:24 PM.
Super Member
Joined: Feb 2023
Posts: 728
Likes: 271
2011 GLK 350 4Matic
Ack... those things are noisy! ;-)
What I do when I'm chasing something like this (sounds like a vacuum leak, but could be pressure escaping) is to get a few feet of hose of some sort, stick one end in my ear (loosely) and poke the other end around until it's obvious where it's coming from. Kind of the equivalent of a mechanic's stethoscope for non-mechanical noises (only even cheaper)! ;-)
What I do when I'm chasing something like this (sounds like a vacuum leak, but could be pressure escaping) is to get a few feet of hose of some sort, stick one end in my ear (loosely) and poke the other end around until it's obvious where it's coming from. Kind of the equivalent of a mechanic's stethoscope for non-mechanical noises (only even cheaper)! ;-)
MBWorld Fanatic!
Joined: Jul 2012
Posts: 1,369
Likes: 319
From: WI
GLK 250
There is no mechanical linkage to control the throttle from under the hood. Those days are gone.
I think by "diesel fumes" you're probably referring to diesel engine exhaust smell, which leads me to believe the EGR area is where it might be originating from. Could be something as simple as a loose bolt on the EGR valve where exhaust is escaping, or a cracked metal flex pipe in the EGR pathway.
Is there any sooty deposit anywhere there shouldn't be? That would help pinpoint the source.
Likely you've had the AEM work done, which means the entire exhaust system is covered for 4yrs/48k miles from that work. If you can't find the source, both from above or below, you may need to schedule a visit to your local stealership and tell them you're smelling exhaust fumes in the car. That's usually a red flag to get you in for service ASAP.
The only other thing I can think of is perhaps the PCV system, like the valve itself. If it's failed it can create too much pressure in the crankcase and can lead to blow outs in weak connections. In severe cases it can also blow out oil seals, so I would double-check the valve is clean and operating as supposed to.
I think by "diesel fumes" you're probably referring to diesel engine exhaust smell, which leads me to believe the EGR area is where it might be originating from. Could be something as simple as a loose bolt on the EGR valve where exhaust is escaping, or a cracked metal flex pipe in the EGR pathway.
Is there any sooty deposit anywhere there shouldn't be? That would help pinpoint the source.
Likely you've had the AEM work done, which means the entire exhaust system is covered for 4yrs/48k miles from that work. If you can't find the source, both from above or below, you may need to schedule a visit to your local stealership and tell them you're smelling exhaust fumes in the car. That's usually a red flag to get you in for service ASAP.
The only other thing I can think of is perhaps the PCV system, like the valve itself. If it's failed it can create too much pressure in the crankcase and can lead to blow outs in weak connections. In severe cases it can also blow out oil seals, so I would double-check the valve is clean and operating as supposed to.
Last edited by andreigbs; Mar 7, 2023 at 02:47 PM.
Thread Starter
Member
Joined: Nov 2015
Posts: 133
Likes: 11
From: Campbell, CA (San Francisco Bay Area)
2013 GLK250, 2022 Tesla MYLR, 1997 Correct Craft Ski Nautique
There is no mechanical linkage to control the throttle from under the hood. Those days are gone.
I think by "diesel fumes" you're probably referring to diesel engine exhaust smell, which leads me to believe the EGR area is where it might be originating from. Could be something as simple as a loose bolt on the EGR valve where exhaust is escaping, or a cracked metal flex pipe in the EGR pathway.
Is there any sooty deposit anywhere there shouldn't be? That would help pinpoint the source.
Likely you've had the AEM work done, which means the entire exhaust system is covered for 4yrs/48k miles from that work. If you can't find the source, both from above or below, you may need to schedule a visit to your local stealership and tell them you're smelling exhaust fumes in the car. That's usually a red flag to get you in for service ASAP.
The only other thing I can think of is perhaps the PCV system, like the valve itself. If it's failed it can create too much pressure in the crankcase and can lead to blow outs in weak connections. In severe cases it can also blow out oil seals, so I would double-check the valve is clean and operating as supposed to.
I think by "diesel fumes" you're probably referring to diesel engine exhaust smell, which leads me to believe the EGR area is where it might be originating from. Could be something as simple as a loose bolt on the EGR valve where exhaust is escaping, or a cracked metal flex pipe in the EGR pathway.
Is there any sooty deposit anywhere there shouldn't be? That would help pinpoint the source.
Likely you've had the AEM work done, which means the entire exhaust system is covered for 4yrs/48k miles from that work. If you can't find the source, both from above or below, you may need to schedule a visit to your local stealership and tell them you're smelling exhaust fumes in the car. That's usually a red flag to get you in for service ASAP.
The only other thing I can think of is perhaps the PCV system, like the valve itself. If it's failed it can create too much pressure in the crankcase and can lead to blow outs in weak connections. In severe cases it can also blow out oil seals, so I would double-check the valve is clean and operating as supposed to.
Sorry about the youtube link. I could have sworn I posted it not only in the text, but in the field for links (and this is the only forum I've posted this on). I didn't realize no-one had been able to see/hear it.
Bummer you can't rev from the engine and have to have someone do it for you. But not surprising. I was just hoping....
I have not noticed a bunch of soot; in fact most of the engine is cleaner than I would expect. But I'll keep looking (with the stethoscope or hose).
Are you saying that this should be covered under the AEM warranty? That would be nice but I definitely want to be sure whatever it is is in fact covered before I take it in. They'll charge for just a glance my way if it is not covered. Where are the EGR and PVC valves on this engine? Anyone have a picture or diagram that shows the locations? I'm not recognizing anything but I don't know what they are supposed to look like on this engine. Don't know enough about diesels and suspect they are different and probably in different locations than my previous vehicles.
MBWorld Fanatic!
Joined: Jul 2012
Posts: 1,369
Likes: 319
From: WI
GLK 250
The EGR is on the driver's side of the engine, under the plastic-covered EGR cooler you're actually pointing to in your video. You can also see the metal flex pipe that looks like an S under the cooler. (Here's an exploded view of that side of the engine, with parts label and diagram OM651 EGR). The cooler is part# 10 and has a black plastic cover on top; the metal flex S-pipe is part# 150.
Having said that, and after playing the vid a few more times, it sounds like boost pressure escaping when letting off the throttle. It's quiet at idle because there's no pressure, but there is some being built up when you give it some Go pedal (even in Park or neutral).
So I'm wondering if you have a bad boost hose off the intercooler, or if you're recently replaced it and it may a loose clip or another tear in the hose itself.
If you've never checked the boost pipe, it's the most likely culprit. If you can rule it out for sure, then back to the EGR system.
The PCV valve is on top of the engine valve cover and towards the passenger side.
Edit: if the intercooler hose is bad, you would be getting exhaust fumes since those are mixed with fresh air when being forced back into the engine for combustion. The only way to make sure it's not the boost hose is to take it off and inspect it closely.
Having said that, and after playing the vid a few more times, it sounds like boost pressure escaping when letting off the throttle. It's quiet at idle because there's no pressure, but there is some being built up when you give it some Go pedal (even in Park or neutral).
So I'm wondering if you have a bad boost hose off the intercooler, or if you're recently replaced it and it may a loose clip or another tear in the hose itself.
If you've never checked the boost pipe, it's the most likely culprit. If you can rule it out for sure, then back to the EGR system.
The PCV valve is on top of the engine valve cover and towards the passenger side.
Edit: if the intercooler hose is bad, you would be getting exhaust fumes since those are mixed with fresh air when being forced back into the engine for combustion. The only way to make sure it's not the boost hose is to take it off and inspect it closely.
Last edited by andreigbs; Mar 13, 2023 at 12:41 PM. Reason: To add info
Thread Starter
Member
Joined: Nov 2015
Posts: 133
Likes: 11
From: Campbell, CA (San Francisco Bay Area)
2013 GLK250, 2022 Tesla MYLR, 1997 Correct Craft Ski Nautique
The EGR is on the driver's side of the engine, under the plastic-covered EGR cooler you're actually pointing to in your video. You can also see the metal flex pipe that looks like an S under the cooler. (Here's an exploded view of that side of the engine, with parts label and diagram OM651 EGR). The cooler is part# 10 and has a black plastic cover on top; the metal flex S-pipe is part# 150.
Having said that, and after playing the vid a few more times, it sounds like boost pressure escaping when letting off the throttle. It's quiet at idle because there's no pressure, but there is some being built up when you give it some Go pedal (even in Park or neutral).
So I'm wondering if you have a bad boost hose off the intercooler, or if you're recently replaced it and it may a loose clip or another tear in the hose itself.
If you've never checked the boost pipe, it's the most likely culprit. If you can rule it out for sure, then back to the EGR system.
The PCV valve is on top of the engine valve cover and towards the passenger side.
Edit: if the intercooler hose is bad, you would be getting exhaust fumes since those are mixed with fresh air when being forced back into the engine for combustion. The only way to make sure it's not the boost hose is to take it off and inspect it closely.
Having said that, and after playing the vid a few more times, it sounds like boost pressure escaping when letting off the throttle. It's quiet at idle because there's no pressure, but there is some being built up when you give it some Go pedal (even in Park or neutral).
So I'm wondering if you have a bad boost hose off the intercooler, or if you're recently replaced it and it may a loose clip or another tear in the hose itself.
If you've never checked the boost pipe, it's the most likely culprit. If you can rule it out for sure, then back to the EGR system.
The PCV valve is on top of the engine valve cover and towards the passenger side.
Edit: if the intercooler hose is bad, you would be getting exhaust fumes since those are mixed with fresh air when being forced back into the engine for combustion. The only way to make sure it's not the boost hose is to take it off and inspect it closely.
Thread Starter
Member
Joined: Nov 2015
Posts: 133
Likes: 11
From: Campbell, CA (San Francisco Bay Area)
2013 GLK250, 2022 Tesla MYLR, 1997 Correct Craft Ski Nautique
So I'm wondering if you have a bad boost hose off the intercooler, or if you're recently replaced it and it may a loose clip or another tear in the hose itself.
If you've never checked the boost pipe, it's the most likely culprit. If you can rule it out for sure, then back to the EGR system.
The PCV valve is on top of the engine valve cover and towards the passenger side.
Edit: if the intercooler hose is bad, you would be getting exhaust fumes since those are mixed with fresh air when being forced back into the engine for combustion. The only way to make sure it's not the boost hose is to take it off and inspect it closely.
MBWorld Fanatic!
Joined: Jun 2021
Posts: 1,919
Likes: 522
From: New Hampsha
'17 GLS450, '14 GLK250, Grandpa's Roadster
Member
Joined: May 2015
Posts: 96
Likes: 25
From: Calgary, AB, Canada
2015 GLK 250 BlueTec with AMG Sport package.
It is most likely your driver-side intercooler hose is failing. Take it off and inspect it closely. When mine failed, I couldn't see a tear, only felt it with my hand and after I took it off it was pretty obvious. Under boost pressure, the hose expands so it will be much louder than when idling. If there is a tear it will be at the top of the hose, in the area closest to the chassis.
Also, there is a small chance your vacuum tank may be split (black plastic thing you're touching in your video around 0:15) OR small hoses that connect to it may have been left unplugged. Check that too. Here is a vacuum system diagram
Also, there is a small chance your vacuum tank may be split (black plastic thing you're touching in your video around 0:15) OR small hoses that connect to it may have been left unplugged. Check that too. Here is a vacuum system diagram
MBWorld Fanatic!
Joined: Jul 2012
Posts: 1,369
Likes: 319
From: WI
GLK 250
Also, there is a small chance your vacuum tank may be split (black plastic thing you're touching in your video around 0:15) OR small hoses that connect to it may have been left unplugged. Check that too. Here is a vacuum system diagram
Thread Starter
Member
Joined: Nov 2015
Posts: 133
Likes: 11
From: Campbell, CA (San Francisco Bay Area)
2013 GLK250, 2022 Tesla MYLR, 1997 Correct Craft Ski Nautique
It is most likely your driver-side intercooler hose is failing. Take it off and inspect it closely. When mine failed, I couldn't see a tear, only felt it with my hand and after I took it off it was pretty obvious. Under boost pressure, the hose expands so it will be much louder than when idling. If there is a tear it will be at the top of the hose, in the area closest to the chassis.
Also, there is a small chance your vacuum tank may be split (black plastic thing you're touching in your video around 0:15) OR small hoses that connect to it may have been left unplugged. Check that too. Here is a vacuum system diagram
Also, there is a small chance your vacuum tank may be split (black plastic thing you're touching in your video around 0:15) OR small hoses that connect to it may have been left unplugged. Check that too. Here is a vacuum system diagram
I was going to change both turbo hoses; bought both from Amazon. However, even though Amazon said they fit the GLK250, neither did. That said, I could not feel any crack or tear, so I removed both and inspected them. Neither are compromised/damaged or torn, so I put them back on.
Can anyone suggest other items to look at? Not sure what is what; here's a picture.
Thanks!!
