GL350 front engine is covered with oil and the serpentine belt is worn out
Thread Starter
Junior Member
Joined: May 2011
Posts: 32
Likes: 3
From: Newport News, VA
95 E300, 02 C230K, 12 GL350
tracing a leak at the front of my 642, from the intake pipe dripping onto the belt at the alternator. Would love to see the pic you mention and the metal ring before I take it apart (again). Just did cooler seals and pretty sure i replaced every gasket and o-ring possible...
Please see blue arrow. The ring was not pushed all the way in and the O ring was not positioned in the right place.
Hope this helps.
Newbie
Joined: Apr 2021
Posts: 10
Likes: 3
2008 GL320
Thanks for following up! My leak is from the other end of the intercooler, but I will check that side as well.
I went to take it apart to look for the ring and noticed two bolts missing that hold the metal part to the plastic part- there is on o-ring between so this is likely my issue. Haven't test driven yet. Not sure if I accidentally removed them when I did the oil cooler job or was left off by another shop. Clogged air filters and wrecked turbo intake seals tells me whoever last had it apart wasn't paying attention.
I went to take it apart to look for the ring and noticed two bolts missing that hold the metal part to the plastic part- there is on o-ring between so this is likely my issue. Haven't test driven yet. Not sure if I accidentally removed them when I did the oil cooler job or was left off by another shop. Clogged air filters and wrecked turbo intake seals tells me whoever last had it apart wasn't paying attention.
Thread Starter
Junior Member
Joined: May 2011
Posts: 32
Likes: 3
From: Newport News, VA
95 E300, 02 C230K, 12 GL350
No problem.
When I had this problem, I replaced all the O-rings so I would not have any issues in the future.
I know what you mean. I bought the car from a local dealer and whomever worked on it was not professional at all. Since then, I had to replace all suspension air bags and 2 air suspension compressors. The last time the compressor went bad it developed a internal short in one of the motor windings. When the compressor was running it was drawing almost 80A and blowing the 40A fuse instantly. I also had to replace the DEF heater.
I heard about the oil cooler problems. So far, it has not given me a problem. Hopefully it will be a while until I have to do it.
If there is anything else I can assist. Please let me know.
Thanks,
When I had this problem, I replaced all the O-rings so I would not have any issues in the future.
I know what you mean. I bought the car from a local dealer and whomever worked on it was not professional at all. Since then, I had to replace all suspension air bags and 2 air suspension compressors. The last time the compressor went bad it developed a internal short in one of the motor windings. When the compressor was running it was drawing almost 80A and blowing the 40A fuse instantly. I also had to replace the DEF heater.
I heard about the oil cooler problems. So far, it has not given me a problem. Hopefully it will be a while until I have to do it.
If there is anything else I can assist. Please let me know.
Thanks,
Last edited by mtclimber; Apr 25, 2021 at 10:02 PM.
Senior Member
Joined: Mar 2017
Posts: 258
Likes: 50
R320, Astro, JSW, ST4
The o-ring on the charge air muffler you've got a blue arrow drawn to, that was my chief suspect for your oil issue.
Another fiddly/iffy MB design choice - I've had more recurring issues getting it to set and Stay positioned correctly, than any other seal.
And guess what - if you hire someone to do anything requiring moving the turbo outlet pipe they will likely take that joint apart and again likely, mess up putting it back together.
It typically leaks backward behind the muffler onto the block and dripping down the back of the muffler and onto the belt.
It doesn't necessarily make enough noise to attract attention under load, and not enough boost leak to throw a code (usually).
Regarding the serpentine belt, make sure the replacement has the same number of ribs as are on your pulleys.
Also make sure All the grooved pulleys have the same number of grooves in them.
It's possible since the car is new to you, that someone in the past put an accessory or even the crank pulley, with a different number of ribs/grooves.
Another fiddly/iffy MB design choice - I've had more recurring issues getting it to set and Stay positioned correctly, than any other seal.
And guess what - if you hire someone to do anything requiring moving the turbo outlet pipe they will likely take that joint apart and again likely, mess up putting it back together.
It typically leaks backward behind the muffler onto the block and dripping down the back of the muffler and onto the belt.
It doesn't necessarily make enough noise to attract attention under load, and not enough boost leak to throw a code (usually).
Regarding the serpentine belt, make sure the replacement has the same number of ribs as are on your pulleys.
Also make sure All the grooved pulleys have the same number of grooves in them.
It's possible since the car is new to you, that someone in the past put an accessory or even the crank pulley, with a different number of ribs/grooves.
Junior Member
Joined: Dec 2020
Posts: 23
Likes: 10
2011 GL350
This looks like the oil filter housing leak. I just had one. easy fix. I also put a video up here.
Typically the oil drips off the bottom of the housing and hits the belt. then its flung all over the front end of the engine bay. Lucky its an easy fix. be sure to clean everything really good and check pully wear when you change the belt.
Typically the oil drips off the bottom of the housing and hits the belt. then its flung all over the front end of the engine bay. Lucky its an easy fix. be sure to clean everything really good and check pully wear when you change the belt.
Senior Member
Joined: Mar 2017
Posts: 258
Likes: 50
R320, Astro, JSW, ST4
^^ This, too.
Careful pulling these items and putting them back - is easy to over-torque many of the fasteners in this area and either snap a bolt or strip the tapped threads in various castings.
Careful pulling these items and putting them back - is easy to over-torque many of the fasteners in this area and either snap a bolt or strip the tapped threads in various castings.
Newbie
Joined: Oct 2017
Posts: 8
Likes: 2
2009 E63 AMG AND 2010 GL350 bluetec
Hello all.
I need to interject and make sure that before calling the turbo bad, assuming it needs a rebuild, check the ccv, qnd consider putting a mann hummel provent between the ccv and the crankcase heater valve that sits in the Y Snorkel. Additionally for belt that is throwing, check that your Alternator pulley or OAP. And if it is the Alternator Pulley, cross reference the INA replacement instead of paying hundreds pay <50 bucks.
After the oil leak is solved and isn't flowing through your turbo and intercooler, clean the intake tract... intercooler, throttle actuator, egr pipe... and do not put everything back on the road until you pop off your egr and clean it... or it will dry up and stick... especially after the oil dries up.
Cheers!
I need to interject and make sure that before calling the turbo bad, assuming it needs a rebuild, check the ccv, qnd consider putting a mann hummel provent between the ccv and the crankcase heater valve that sits in the Y Snorkel. Additionally for belt that is throwing, check that your Alternator pulley or OAP. And if it is the Alternator Pulley, cross reference the INA replacement instead of paying hundreds pay <50 bucks.
After the oil leak is solved and isn't flowing through your turbo and intercooler, clean the intake tract... intercooler, throttle actuator, egr pipe... and do not put everything back on the road until you pop off your egr and clean it... or it will dry up and stick... especially after the oil dries up.
Cheers!
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Thread Starter
Junior Member
Joined: May 2011
Posts: 32
Likes: 3
From: Newport News, VA
95 E300, 02 C230K, 12 GL350
Thanks B34chBum
Good points.
When I got the car, it drove nice. I looked at the engine and everything was great looking. My wife drove it until it was time for its service and when I opened up the hood, it had oil all over the place, Not to mention that someone used the flat idler pulley instead of a grooved one and shredded the belt to pieces. I went through 3 belts in about a 3 week. One from AutoZone and the others were MB parts. I will never purchase a car from the local MB dealer. My father also had problems with the Mercedes he purchased at the local MB's... and there are two.
I will never let any one work on my cars. I can, and have done all the work my self on all my MB's
Thanks,
Good points.
When I got the car, it drove nice. I looked at the engine and everything was great looking. My wife drove it until it was time for its service and when I opened up the hood, it had oil all over the place, Not to mention that someone used the flat idler pulley instead of a grooved one and shredded the belt to pieces. I went through 3 belts in about a 3 week. One from AutoZone and the others were MB parts. I will never purchase a car from the local MB dealer. My father also had problems with the Mercedes he purchased at the local MB's... and there are two.
I will never let any one work on my cars. I can, and have done all the work my self on all my MB's
Thanks,
Newbie
Joined: May 2021
Posts: 6
Likes: 0
From: B.C
2012 Mercedes GL350
I still have not figured this out. Purchased the O rings. Installed them, along with the new serpentine belt and the grooved idler pulley. Last week my wife called me and she said that she heard a noise and the steering wheel got stiff. I told her to turn around and go home. Luckily she was not too far from home. When I looked at the car the serpentine belt was gone and was wrapped around all the pulleys. Friday went to the dealer, got a new belt and took off all the things in front of the engine that has an O ring. I also checked the turbo and the impeller has play. Does any one know where I can get a rebuilt kit for the turbo? I will upload the video shortly.
Last edited by Irfan Hassan; Sep 18, 2025 at 11:23 PM.
Senior Member
Joined: Aug 2018
Posts: 410
Likes: 122
From: Kelowna, BC
08 GL320 CDI
The cause of the worn out belts? I know! I know!
it happened to my GL a few times, then I realized I was buying the wrong belt. There are 7 spline and 8 spline pulleys. I was buying the wrong spline count belt for mine. Even though different stores said it was correct. I physically counted the ribs on all the pulleys and bought the correct one. Been 4 years now. Belt is still smooth and clean.
it happened to my GL a few times, then I realized I was buying the wrong belt. There are 7 spline and 8 spline pulleys. I was buying the wrong spline count belt for mine. Even though different stores said it was correct. I physically counted the ribs on all the pulleys and bought the correct one. Been 4 years now. Belt is still smooth and clean.
MBWorld Fanatic!
Joined: Jan 2010
Posts: 3,116
Likes: 782
NGL450 w/EORP, S550
The cause of the worn out belts? I know! I know!
it happened to my GL a few times, then I realized I was buying the wrong belt. There are 7 spline and 8 spline pulleys. I was buying the wrong spline count belt for mine. Even though different stores said it was correct. I physically counted the ribs on all the pulleys and bought the correct one. Been 4 years now. Belt is still smooth and clean.
it happened to my GL a few times, then I realized I was buying the wrong belt. There are 7 spline and 8 spline pulleys. I was buying the wrong spline count belt for mine. Even though different stores said it was correct. I physically counted the ribs on all the pulleys and bought the correct one. Been 4 years now. Belt is still smooth and clean.
Newbie
Joined: Nov 2025
Posts: 3
Likes: 0
From: Chicago
ML350 Bluetec
New here and am having the exact same problem. I’m sorry to bring this old post back up but I wanted to make sure, the metal ring needs to be pushed down all the way in the plastic? So the only visible part is the metal lip?
Newbie
Joined: Dec 2021
Posts: 3
Likes: 0
From: Margaret River, Western Australia
GL350 X164
Oft overlooked
Don’t neglect the vacuum pump, can leak profusely. Pump to head gasket readily available but rarely the issue, the front cover on the pump is more likely to leak and no seal is available so you’ll need to improvise with some gasket in a tube.
happy leak hunting
happy leak hunting
Newbie
Joined: Nov 2025
Posts: 3
Likes: 0
From: Chicago
ML350 Bluetec
had the same issue as OP. Pushed that metal piece down and no leaks. I feel like its matter of time before it makes its way out again, maybe I will replace if it starts leaking again.
