Sticky timing chain tensioner? Intermittent brief rattle on startup
Thread Starter
MBWorld Fanatic!
Joined: Jun 2010
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From: Emmett, ID, USA
2007 GL450
Sticky timing chain tensioner? Intermittent brief rattle on startup
I normally let the engine idle for a few seconds at cold start to allow the oil pressure to come up and the idle speed to stabilize. The engine quiets down and settles at about 1200 rpm.
Recently, the engine began suffering an intermittent and brief (approx. half second) rattle during this startup process. The rattle is not loud and is consistent with the rest of the startup noises, but is definitely additional.
The engine speed drops by about 200 rpm, from 1,200 down to 1,000, when this happens. When the rattle stops, the idle rpm recovers.
This noise does not happen during warm starts nor warm operation.
There was a logged P0016 code two weeks ago. This code has not recurred, neither logged nor pending.
Thoughts?
Recently, the engine began suffering an intermittent and brief (approx. half second) rattle during this startup process. The rattle is not loud and is consistent with the rest of the startup noises, but is definitely additional.
The engine speed drops by about 200 rpm, from 1,200 down to 1,000, when this happens. When the rattle stops, the idle rpm recovers.
This noise does not happen during warm starts nor warm operation.
There was a logged P0016 code two weeks ago. This code has not recurred, neither logged nor pending.
Thoughts?
Last edited by eric_in_sd; Jun 17, 2026 at 09:32 AM.
Member
Joined: Apr 2011
Posts: 182
Likes: 74
From: Denver
2005 ML500, 2011 E350 4M, 2012 GL550
Its a 2007 right? Don`t hold me for that but I remember reading somewhere 2007s and some early 2008s have a weak idler gear and prone to fail. I`m more familiar with the M272 issues back then since I had a E350.
Also not too long ago there was a member from Texas in this forum and he had to part with the car due to a similar or same issue.
Hope yours turns out a stupid magnet or something easier, cheaper, otherwise the writing is on the wall, how many miles you have now Eric?
Also not too long ago there was a member from Texas in this forum and he had to part with the car due to a similar or same issue.
Hope yours turns out a stupid magnet or something easier, cheaper, otherwise the writing is on the wall, how many miles you have now Eric?
Thread Starter
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,787
Likes: 646
From: Emmett, ID, USA
2007 GL450
Its a 2007 right? Don`t hold me for that but I remember reading somewhere 2007s and some early 2008s have a weak idler gear and prone to fail. I`m more familiar with the M272 issues back then since I had a E350.
Also not too long ago there was a member from Texas in this forum and he had to part with the car due to a similar or same issue.
Hope yours turns out a stupid magnet or something easier, cheaper, otherwise the writing is on the wall, how many miles you have now Eric?
Also not too long ago there was a member from Texas in this forum and he had to part with the car due to a similar or same issue.
Hope yours turns out a stupid magnet or something easier, cheaper, otherwise the writing is on the wall, how many miles you have now Eric?
I'm puzzled why the rpm would drop when it's rattling. I hope it's not wearing the guides or block, doing something horrible that drags down the rpm when it does the rattle. I'll have to look for Glitter of Death when I next change the oil. It's hard for me to imagine the rattle dragging the engine; it just isn't that loud. Maybe it's fluctuating cam timing, which the ECU doesn't notice because it's in open loop mode? The tensioner has a ratchet mechanism, but maybe it is at the end of the ratchet travel (yikes).
The motor now has 225K miles and runs marvelously otherwise. I have not heard of timing chain stretch being a problem for these motors, so - I'm hopeful.
Thread Starter
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,787
Likes: 646
From: Emmett, ID, USA
2007 GL450
Or maybe it's this ... has to do with the VVT (but I thought the M273 variable valve timing is electrical, not vacuum ... I never looked closely, tho) ... this would help explain why the rpms drop; it's a valve noise, not timing chain slap
This update relates to ALL engines from 1995 to today. Cold srart clatter, clanking, rattle: It's not the chain tensioner or the timing chain at all. Unless you have over 250k on odometer or have not changed the oil every 5,000-7,000 miles, the noise you hear is from the VVT valve timing system and is easily remedied. All VVT engines will make a noise after sitting for more than 3 days. However, some do not make the noise by which we can hear them. The noise is indicative of a lack of full oil pressure at the lifter sprockets on the cam and VVT mechanisms.
There is nothing wrong with the engine. It probably has been making this noise since day one. If your windows are shut when you start the car after sitting for a few days, or even overnight in temps below 70 (f), you will hear that noise after a second past ignition and it will last for 1-2 seconds and stop.
To fix the problem, simply press the brake pedal firmly, not by smashing it, but by pressing it as if you were traveling at 40mph and had to slow down a bit. Press the pedal 2 times, and before starting, press the brake pedal firmly and start the car while pressing that brake pedal. The result will be to create a "vacuum pull" in the valve train and intake manifold, simulating the sane vacuum force created within the engine when it's running.
Simply press firmly on the brake pedal twice, then prior to turning the key, simply press the pedal firmly a third time, but hold it, start the car, and release the pedal. No more noise; guaranteed.
I learned this when I had the same cold start noise on a 2002 GS 300 as well as a 2007 GS350. Both had VVT valve systems. You see, all VVT engines use vacuum as well as hydraulic and electric/mechanical aspects to the variable valve timing.
It's not really a design flaw in any of these engines, at least not the or any other car I've owned. Usually, a TSB will be issued if customers complain enough about the fears that their engines are grinding. Most TSB's for valve clatter on cold start involve changing the vacuum orifices in either the power brake systems or at the camshafts. It's so much easier just to create a simulated vacuum pull by pressing firmly on the brake pedal a few times then holding the pedal firmly when cold starting. Once the engines fires, let go of the brake pedal and you will not hear a rattle, clank, etc.
I've found this out by studying engine schematics on , , Audi, Chevy, , and even Chrysler products. Each time a friend would complain about cold start clanking/clatter, I would advise them to try my method and they all reported that the noise was gone.
Try leaving your car for as long as it takes to simulate that clatter. (for my R170) it was always 5+ days. If it is only 24 hours, overnight, or three weeks, just try my method and you'll see your noise is gone. My friends R171 has 272k on the odometer, and he replaced his timing chain tensioner three times and it did nothing to stop the clatter. Once he started the car using my 2 second fix, his noise went away.
Now, if you allowed OCI's of 10k miles for 150,000 miles and used a less than wonderful oil blend, you could have a partially clogged timing chain tensioner. However, the difference between cold start valve clatter and timing chain clanking is night v. day. Timing chain clatter does NOT appear only on cold starts and sound much different.
Please let me know how this starting procedure works. Oh, no need to ever bother with a warm engine. Vacuum remains in all engines for up to 12 hours.
https://www.benzworld.org/threads/co...odels.3032728/
There is nothing wrong with the engine. It probably has been making this noise since day one. If your windows are shut when you start the car after sitting for a few days, or even overnight in temps below 70 (f), you will hear that noise after a second past ignition and it will last for 1-2 seconds and stop.
To fix the problem, simply press the brake pedal firmly, not by smashing it, but by pressing it as if you were traveling at 40mph and had to slow down a bit. Press the pedal 2 times, and before starting, press the brake pedal firmly and start the car while pressing that brake pedal. The result will be to create a "vacuum pull" in the valve train and intake manifold, simulating the sane vacuum force created within the engine when it's running.
Simply press firmly on the brake pedal twice, then prior to turning the key, simply press the pedal firmly a third time, but hold it, start the car, and release the pedal. No more noise; guaranteed.
I learned this when I had the same cold start noise on a 2002 GS 300 as well as a 2007 GS350. Both had VVT valve systems. You see, all VVT engines use vacuum as well as hydraulic and electric/mechanical aspects to the variable valve timing.
It's not really a design flaw in any of these engines, at least not the or any other car I've owned. Usually, a TSB will be issued if customers complain enough about the fears that their engines are grinding. Most TSB's for valve clatter on cold start involve changing the vacuum orifices in either the power brake systems or at the camshafts. It's so much easier just to create a simulated vacuum pull by pressing firmly on the brake pedal a few times then holding the pedal firmly when cold starting. Once the engines fires, let go of the brake pedal and you will not hear a rattle, clank, etc.
I've found this out by studying engine schematics on , , Audi, Chevy, , and even Chrysler products. Each time a friend would complain about cold start clanking/clatter, I would advise them to try my method and they all reported that the noise was gone.
Try leaving your car for as long as it takes to simulate that clatter. (for my R170) it was always 5+ days. If it is only 24 hours, overnight, or three weeks, just try my method and you'll see your noise is gone. My friends R171 has 272k on the odometer, and he replaced his timing chain tensioner three times and it did nothing to stop the clatter. Once he started the car using my 2 second fix, his noise went away.
Now, if you allowed OCI's of 10k miles for 150,000 miles and used a less than wonderful oil blend, you could have a partially clogged timing chain tensioner. However, the difference between cold start valve clatter and timing chain clanking is night v. day. Timing chain clatter does NOT appear only on cold starts and sound much different.
Please let me know how this starting procedure works. Oh, no need to ever bother with a warm engine. Vacuum remains in all engines for up to 12 hours.
MBWorld God!
Joined: Dec 2019
Posts: 33,393
Likes: 6,624
Or maybe it's this ... has to do with the VVT (but I thought the M273 variable valve timing is electrical, not vacuum ... I never looked closely, tho) ... this would help explain why the rpms drop; it's a valve noise, not timing chain slap
This update relates to ALL engines from 1995 to today. Cold srart clatter, clanking, rattle: It's not the chain tensioner or the timing chain at all. Unless you have over 250k on odometer or have not changed the oil every 5,000-7,000 miles, the noise you hear is from the VVT valve timing system and is easily remedied. All VVT engines will make a noise after sitting for more than 3 days. However, some do not make the noise by which we can hear them. The noise is indicative of a lack of full oil pressure at the lifter sprockets on the cam and VVT mechanisms.
There is nothing wrong with the engine. It probably has been making this noise since day one. If your windows are shut when you start the car after sitting for a few days, or even overnight in temps below 70 (f), you will hear that noise after a second past ignition and it will last for 1-2 seconds and stop.
To fix the problem, simply press the brake pedal firmly, not by smashing it, but by pressing it as if you were traveling at 40mph and had to slow down a bit. Press the pedal 2 times, and before starting, press the brake pedal firmly and start the car while pressing that brake pedal. The result will be to create a "vacuum pull" in the valve train and intake manifold, simulating the sane vacuum force created within the engine when it's running.
Simply press firmly on the brake pedal twice, then prior to turning the key, simply press the pedal firmly a third time, but hold it, start the car, and release the pedal. No more noise; guaranteed.
I learned this when I had the same cold start noise on a 2002 Lexus GS 300 as well as a 2007 Lexus GS350. Both had VVT valve systems. You see, all VVT engines use vacuum as well as hydraulic and electric/mechanical aspects to the variable valve timing.
It's not really a design flaw in any of these engines, at least not the SLK or any other car I've owned. Usually, a TSB will be issued if customers complain enough about the fears that their engines are grinding. Most TSB's for valve clatter on cold start involve changing the vacuum orifices in either the power brake systems or at the camshafts. It's so much easier just to create a simulated vacuum pull by pressing firmly on the brake pedal a few times then holding the pedal firmly when cold starting. Once the engines fires, let go of the brake pedal and you will not hear a rattle, clank, etc.
I've found this out by studying engine schematics on Mercedes, BMW, Audi, Chevy, Ford, Toyota and even Chrysler products. Each time a friend would complain about cold start clanking/clatter, I would advise them to try my method and they all reported that the noise was gone.
Try leaving your car for as long as it takes to simulate that clatter. (for my R170) it was always 5+ days. If it is only 24 hours, overnight, or three weeks, just try my method and you'll see your noise is gone. My friends R171 has 272k on the odometer, and he replaced his timing chain tensioner three times and it did nothing to stop the clatter. Once he started the car using my 2 second fix, his noise went away.
Now, if you allowed OCI's of 10k miles for 150,000 miles and used a less than wonderful oil blend, you could have a partially clogged timing chain tensioner. However, the difference between cold start valve clatter and timing chain clanking is night v. day. Timing chain clatter does NOT appear only on cold starts and sound much different.
Please let me know how this starting procedure works. Oh, no need to ever bother with a warm engine. Vacuum remains in all engines for up to 12 hours.
https://www.benzworld.org/threads/co...odels.3032728/There is nothing wrong with the engine. It probably has been making this noise since day one. If your windows are shut when you start the car after sitting for a few days, or even overnight in temps below 70 (f), you will hear that noise after a second past ignition and it will last for 1-2 seconds and stop.
To fix the problem, simply press the brake pedal firmly, not by smashing it, but by pressing it as if you were traveling at 40mph and had to slow down a bit. Press the pedal 2 times, and before starting, press the brake pedal firmly and start the car while pressing that brake pedal. The result will be to create a "vacuum pull" in the valve train and intake manifold, simulating the sane vacuum force created within the engine when it's running.
Simply press firmly on the brake pedal twice, then prior to turning the key, simply press the pedal firmly a third time, but hold it, start the car, and release the pedal. No more noise; guaranteed.
I learned this when I had the same cold start noise on a 2002 Lexus GS 300 as well as a 2007 Lexus GS350. Both had VVT valve systems. You see, all VVT engines use vacuum as well as hydraulic and electric/mechanical aspects to the variable valve timing.
It's not really a design flaw in any of these engines, at least not the SLK or any other car I've owned. Usually, a TSB will be issued if customers complain enough about the fears that their engines are grinding. Most TSB's for valve clatter on cold start involve changing the vacuum orifices in either the power brake systems or at the camshafts. It's so much easier just to create a simulated vacuum pull by pressing firmly on the brake pedal a few times then holding the pedal firmly when cold starting. Once the engines fires, let go of the brake pedal and you will not hear a rattle, clank, etc.
I've found this out by studying engine schematics on Mercedes, BMW, Audi, Chevy, Ford, Toyota and even Chrysler products. Each time a friend would complain about cold start clanking/clatter, I would advise them to try my method and they all reported that the noise was gone.
Try leaving your car for as long as it takes to simulate that clatter. (for my R170) it was always 5+ days. If it is only 24 hours, overnight, or three weeks, just try my method and you'll see your noise is gone. My friends R171 has 272k on the odometer, and he replaced his timing chain tensioner three times and it did nothing to stop the clatter. Once he started the car using my 2 second fix, his noise went away.
Now, if you allowed OCI's of 10k miles for 150,000 miles and used a less than wonderful oil blend, you could have a partially clogged timing chain tensioner. However, the difference between cold start valve clatter and timing chain clanking is night v. day. Timing chain clatter does NOT appear only on cold starts and sound much different.
Please let me know how this starting procedure works. Oh, no need to ever bother with a warm engine. Vacuum remains in all engines for up to 12 hours.
Thread Starter
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,787
Likes: 646
From: Emmett, ID, USA
2007 GL450
I have no idea what is going on. There were no links at all in the original post. The edit feature seems gone as well.
While there is a great deal of confusion regarding this cold start rattle problem, I suspect it is the sealing o-rings on the oil pickup tube allowing air to get in and thus drain oil back down into the pan. MB likes o-rings, but they do have a limited life. One can change the o-rings, but that calls for dropping the oil pan, which calls for lifting the enging. Ugh.
While there is a great deal of confusion regarding this cold start rattle problem, I suspect it is the sealing o-rings on the oil pickup tube allowing air to get in and thus drain oil back down into the pan. MB likes o-rings, but they do have a limited life. One can change the o-rings, but that calls for dropping the oil pan, which calls for lifting the enging. Ugh.
MBWorld God!
Joined: Dec 2019
Posts: 33,393
Likes: 6,624
I have no idea what is going on. There were no links at all in the original post. The edit feature seems gone as well.
While there is a great deal of confusion regarding this cold start rattle problem, I suspect it is the sealing o-rings on the oil pickup tube allowing air to get in and thus drain oil back down into the pan. MB likes o-rings, but they do have a limited life. One can change the o-rings, but that calls for dropping the oil pan, which calls for lifting the enging. Ugh.
While there is a great deal of confusion regarding this cold start rattle problem, I suspect it is the sealing o-rings on the oil pickup tube allowing air to get in and thus drain oil back down into the pan. MB likes o-rings, but they do have a limited life. One can change the o-rings, but that calls for dropping the oil pan, which calls for lifting the enging. Ugh.
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Joined: Aug 2018
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From: Kelowna, BC
08 GL320 CDI
Run a liter of ATF in the oil, run it for a day, drain, then try a slightly thicker oil. (used to work in the old days to clean up all the garbage in the system. The ATF has detergents in it.)
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Joined: Jul 2016
Posts: 714
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From: NE OHIO
1998 SL500,2011 GL550,2009 ML350,past 1995 E320 Cabrio ,2005 ML500,2006 ML500,1996 SL500,1972 280SEL
ATF
I actually agree but personally would just run ATF at an idle in the driveway… in the old days..60’s and 70’s we would clean up noisy lifters .
Back to the idle speed … my GL550’s fast idle around 1200 than drop to 500-550… Is that what your 450 idles at ?
On my wife’s 2009 ML350 I had a very familiar rattle around 120k… I did 2 things that help.. replaced the chain tensioner and tightened up the exhaust … it still has a slight rattle at startup but goes away quickly.. the mileage is around 150k now
Back to the idle speed … my GL550’s fast idle around 1200 than drop to 500-550… Is that what your 450 idles at ?
On my wife’s 2009 ML350 I had a very familiar rattle around 120k… I did 2 things that help.. replaced the chain tensioner and tightened up the exhaust … it still has a slight rattle at startup but goes away quickly.. the mileage is around 150k now
Last edited by vesiadog; Jun 20, 2026 at 08:44 PM.
Thread Starter
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,787
Likes: 646
From: Emmett, ID, USA
2007 GL450
my GL550’s fast idle around 1200 than drop to 500-550… Is that what your 450 idles at ?
On my wife’s 2009 ML350 I had a very familiar rattle around 120k… I did 2 things that help.. replaced the chain tensioner and tightened up the exhaust … it still has a slight rattle at startup but goes away quickly.. the mileage is around 150k now
On my wife’s 2009 ML350 I had a very familiar rattle around 120k… I did 2 things that help.. replaced the chain tensioner and tightened up the exhaust … it still has a slight rattle at startup but goes away quickly.. the mileage is around 150k now
I understand the noisiness at startup (for the first two seconds or so) is normal. There is an additional intermittent noise in early startup, in which the idle drops by about 100 rpm for about a second and then recovers. It will only hurt my wallet by about $110 to change the tensioner, so I'll probably do that when the new tensioner arrives.
I am puzzled there does not seem to be a consensus opinion on the cause of the intermittent noise. Air leaking into the pickup tube seems like a plausible explanation: The air bubble is pumped through the oil passages and momentarily relaxes the tensioner?
Super Member
Joined: Jul 2016
Posts: 714
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From: NE OHIO
1998 SL500,2011 GL550,2009 ML350,past 1995 E320 Cabrio ,2005 ML500,2006 ML500,1996 SL500,1972 280SEL
noise
I was quite surprised when we found the exhaust rattle along with the chain tensioner… my first thoughts were the exhaust was making the rattle all along ??? We changed both and it has helped quite a bit. I would check all the bolts on the exhaust just in case…
