2009 E550 M273 warm start knock
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Newbie
Joined: Oct 2021
Posts: 13
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2009 E550
2009 E550 M273 warm start knock
Greetings. Back in November I purchased a very clean 2009 E550 at 98k miles. I really love this car, big upgrade for me over my outgoing CLK, but I have one concern I would like some opinions on. Starting the car cold results in no troubling sounds from the engine, all is normal. When letting the car sit for a while (at least ~1hr) after it has been fully warmed up and then starting it, it creates a deep thumping noise for a few seconds then goes away completely, only to be heard on another "warm" start. The engine runs and sounds perfect other than that start knock. It sounds identical to this video (not my car):
I have done some research on this and I have found some threads that discuss this issue. There seem to be multiple proposed causes, with the most common one being the main bearings either wearing or being improperly designed. Some people claim it's a non issue, others imply the engine needs to be fixed to prevent damage. If anyone knows more about this I would love to know if it's problematic or a characteristic of m273 and m272.
I have done some research on this and I have found some threads that discuss this issue. There seem to be multiple proposed causes, with the most common one being the main bearings either wearing or being improperly designed. Some people claim it's a non issue, others imply the engine needs to be fixed to prevent damage. If anyone knows more about this I would love to know if it's problematic or a characteristic of m273 and m272.
Last edited by AetherSprite; Jan 28, 2022 at 03:30 PM. Reason: Formatting
Thread Starter
Newbie
Joined: Oct 2021
Posts: 13
Likes: 3
2009 E550
So after doing some more digging online, I can confidently say that this knock is harmless, as alarming as it may sound. There are countless reports of this noise on M272 and M273 in forums, and I have not managed to find one scenario where this resulted in engine damage of any sort. I have found some reports of high mileage engines (well over 100k miles) with this knock and they still run fine, with the sound remaining the same. Some owners have been hearing it since new, with no ill effects. As for the reason for the knock, I am sticking with low oil pressure supplied to the main bearings at startup which creates the thumping for a few seconds. I'll be keeping my E550 for quite a while, it's a brilliant car.
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From: Orbiting the planet
This place is a joke.
My 2008 ML350 does this....with 179k miles on the clock! Otherwise runs great. There is a technical bulletin from MB about this. The remedy is to replace the main bearings, but only the upper or lower halves with a tighter clearance set. I don't remember the specifics, but the bulletin did say the noise did not cause any long term problems. For the amount of work it is on my 4matic SUV, I've chosen to leave it alone. I'd rather buy a newer model year used engine if the need ever arises.I have a friend with 215k miles on his 2008 m272 engine.
Junior Member
Joined: Mar 2023
Posts: 29
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2008 W211 E300 4Matic
Update?
Great to hear, I have this noise too on my m272 with 115k miles. Its sounds quite concerning but I dont see why it’d be an issue if its only on warm starts. Plus the m272 makes plenty of unwanted noises😅 like the low idle knock. They dont seem to be fatal. Ive seen some people mention the oil pump pickup tube o ring as a probable cause. But i dont think its the same noise. Anyway, do you still have the noise ? And no problem yet?
Member
Joined: May 2012
Posts: 98
Likes: 19
From: Orange County, CA
08 E350
The forums are full of complaints like this on the M272/273 engines, M272 predominantly. Nothing to worry about, it does that when the oil seeps out when warm and needs some time to get the pressure back up.
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Junior Member
Joined: Oct 2019
Posts: 53
Likes: 7
From: Melbourne, Australia
R320, S211 wagon
My car (2009 S211 E350) use to make the warm start knock. I replaced the oil with Shell Helix Ultra 5w40 and have never heard it knock on warm start.
It also has the slight warm idle knocking sound. I borescoped the cylinders and found heavy scoring in one of the cylinders and minor scuffing on another. Pretty sure there is a TSB on it. Pretty disappointing on a car that has 80,000 miles on it and has been maintained very well. Will be selling it ASAP, and look to get an M113 equiped S211.
I would make sure to borescope your engine to check for scoring and not to make the mistake as I did on spending thousands on preventive maintenance on a car with a bad engine.
I am not saying every m272/m273 has scoring as people claim they have the slight knock on idle and have borescoped their engines and have found nothing. Will miss driving the E350.
It also has the slight warm idle knocking sound. I borescoped the cylinders and found heavy scoring in one of the cylinders and minor scuffing on another. Pretty sure there is a TSB on it. Pretty disappointing on a car that has 80,000 miles on it and has been maintained very well. Will be selling it ASAP, and look to get an M113 equiped S211.
I would make sure to borescope your engine to check for scoring and not to make the mistake as I did on spending thousands on preventive maintenance on a car with a bad engine.
I am not saying every m272/m273 has scoring as people claim they have the slight knock on idle and have borescoped their engines and have found nothing. Will miss driving the E350.
SPONSOR
Joined: Apr 2021
Posts: 846
Likes: 558
From: San Jose, CA
11 E550, 16 AMG GTS, 13 S550
It's normal for me. 4.7L biturbos do this too
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Alpha European Autotech
Purchase Amsoil at 25% off from me
Chris Tran, Retired Alpha European Autotech Owner
Amsoil Independent Dealer #7236674
Alpha European Autotech
Purchase Amsoil at 25% off from me
Chris Tran, Retired Alpha European Autotech Owner
Amsoil Independent Dealer #7236674
Junior Member
Joined: Mar 2023
Posts: 29
Likes: 3
2008 W211 E300 4Matic
My car (2009 S211 E350) use to make the warm start knock. I replaced the oil with Shell Helix Ultra 5w40 and have never heard it knock on warm start.
It also has the slight warm idle knocking sound. I borescoped the cylinders and found heavy scoring in one of the cylinders and minor scuffing on another. Pretty sure there is a TSB on it. Pretty disappointing on a car that has 80,000 miles on it and has been maintained very well. Will be selling it ASAP, and look to get an M113 equiped S211.
I would make sure to borescope your engine to check for scoring and not to make the mistake as I did on spending thousands on preventive maintenance on a car with a bad engine.
I am not saying every m272/m273 has scoring as people claim they have the slight knock on idle and have borescoped their engines and have found nothing. Will miss driving the E350.
It also has the slight warm idle knocking sound. I borescoped the cylinders and found heavy scoring in one of the cylinders and minor scuffing on another. Pretty sure there is a TSB on it. Pretty disappointing on a car that has 80,000 miles on it and has been maintained very well. Will be selling it ASAP, and look to get an M113 equiped S211.
I would make sure to borescope your engine to check for scoring and not to make the mistake as I did on spending thousands on preventive maintenance on a car with a bad engine.
I am not saying every m272/m273 has scoring as people claim they have the slight knock on idle and have borescoped their engines and have found nothing. Will miss driving the E350.
Junior Member
Joined: Jan 2019
Posts: 19
Likes: 11
E350
My '08 E350 has made that exact sound since at least 30k miles. It now has 60k and hasn't changed a bit. I've tried crankcase flushes and different oils, with no improvement. I've resolved to just ignore it.
SPONSOR
Joined: Apr 2021
Posts: 846
Likes: 558
From: San Jose, CA
11 E550, 16 AMG GTS, 13 S550
as much as I'd love to sell you Amsoil, theres not really a remedy. I've done timing chains and tensioner on cars that still have this startup sound later. The dealer likes to sell you the new oil control valve (i'm blanking on the name) and the problem will be there when you start it up after $3000 gone lol
__________________
Alpha European Autotech
Purchase Amsoil at 25% off from me
Chris Tran, Retired Alpha European Autotech Owner
Amsoil Independent Dealer #7236674
Alpha European Autotech
Purchase Amsoil at 25% off from me
Chris Tran, Retired Alpha European Autotech Owner
Amsoil Independent Dealer #7236674
Junior Member
Joined: Jan 2019
Posts: 19
Likes: 11
E350
as much as I'd love to sell you Amsoil, theres not really a remedy. I've done timing chains and tensioner on cars that still have this startup sound later. The dealer likes to sell you the new oil control valve (i'm blanking on the name) and the problem will be there when you start it up after $3000 gone lol
BTW, I do like Amsoil. In another car, TorqueDrive ATF is amazing stuff.
Junior Member
Joined: Oct 2019
Posts: 53
Likes: 7
From: Melbourne, Australia
R320, S211 wagon
I think I was burning a little bit, nothing excessive. After I replaced the whole PCV system, oil consumption seemed to have almost stopped.
