18 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHMetallic sound on morning start up
Leading reported evidence
Replace atf
Suggestion or failed attempt
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
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Read evidence and context
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Suggestion · Original poster
Mercedes stealership told him to change the ATF, change the ignition switch change the controller of the gearbox.
Leading evidence: 'Replace atf' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Replace atf' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion · Original poster
Mercedes forums, suggested to replace the battery.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
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Suggestion · Original poster
Mercedes stealership told him to change the ATF, change the ignition switch change the controller of the gearbox.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
Mercedes stealership told him to change the ATF, change the ignition switch change the controller of the gearbox.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
18 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
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Generation: 20261027T031046Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Hello,
On every morning start up (or when I leave the car for at least 1 hour) and for 1 second, I hear a metallic sound which resembles piston slapping, it is not the sound of a thechain like a can of marbles. It goes away after 1 second and the engine works fine, pulls nice. No CEL, No strange cam deviations. As if oil is getting into a place and sound goes away. Obviously if I switch off and on after 5 minutes I don't get the sound it's only after some time that I suppose the oil drains back to the sump.
Should I be worried? Engine has no bore scoring, scoped 15k ago. The sound was always there. 10w50 Mobil1 +ceratec every 3k miles.
First have someone make a video clip at start up be close to the engine and lid opened
scoping a car 15k ago doesn’t mean it isn’t bore scored now
most likely I would just drive it till shyte happens harder
+2 on the sound clip...
I can diagnose a detailed Technical Symptom from 1k miles away from a good text description, but sounds/noises just don't translate good to text ...
Fail Nr1:
I got to the car this morning with two mobile phones one to record the sound and one to record the video. Video recording never started, sound recording is next to the SAI pump, so I only got airplane ✈️ sounds.
Postponing for tomorrow....
The only thing I noticed is that the sound is clearer from inside the cabin.
Does anyone have a sound clip of this? My knock on my engine is prob from a muffler that has become separated. But I cant seem to find the start metal sound here>?
So I have two MP3 files for you to listen.
On that first start file, pay attention to the sound between second 04 and 06. The sound doesn't come up immediately after engine start, only comes a couple of seconds later. This is the metallic sound I'm talking about.
On the second start 30 seconds after the first start, you can hear the sound is gone telling me that something has been lubricated.
What I hear as difference between the two files, sounds to me as if it is the secondary air injection pump.
Disconnect it and repeat cold start.
Is the noise you refer to now absent?
@isalos
That noise sounds like piston slap to you ???
Seriously , a good description is vital to Automotive mechanical diagnosis....
Your engine is fine...Stop fearing ...
That noise that sounds like a Skill-Saw cutting through a nail is the SAI Pump (Secondary Air Injection Pump)
It is not part of the engine it is just an add-on pump for Emissions...
When new they sound like a vacuum cleaner when running, when they are old and worn/failing they get louder and louder and end up sounding like this or even worse...
Obviously I am knowledgeable enough to know that the thing that sounds like a hairdryer or like an aeroplane is the SAI pump.
Listen again carefully on the 1stStart file between seconds 4-6, you will hear it after 2-3 times. The Knocking sound goes away after that... It is a tick tick tick not the hairdryer sound....
Serious question ........How much $$$$$ would you spend to stop the noise???
Yes after blocking out all the other louder and more annoying noises, I hear the very very faint tapping sound that lasts about 1-2 seconds ...
Seriously I would like to spend 0, but I will spend what is necessary. After spending a lot of years online and hobbying with cars I have found that the knowledge inside forums is far more important to what a mechanic says no matter how experienced he/she is.
For example yesterday my father's c200 Mercedes with the same gearbox as the 996 tiptronic, would stay on first year until you switch off and on the car again. Mercedes stealership told him to change the ATF, change the ignition switch change the controller of the gearbox. Mercedes forums, suggested to replace the battery. Guess what...
Believe it or not I'm one of the good students of porschetech3 legacy. I am not looking to fix the sound I'm looking to understand what the sound might be. My mechanic told me that these are hydraulic lifters, and the second opinion from the most knowledgeable guys is important to me. That's all.
The sound is more prevalent when you're in the car and is not well captured on the soundtrack but this is the best I could.
Yes, it is a hydraulic lifter tap ....
No matter at what position the engine stops at there will always be at least one valve fully open....The spring on that valve is trying to close the valve at a higher pressure than all the other springs that are closed...but all the springs are all pressing against the lifters squeezing the oil out of them...but at least one is squeezing harder than the rest...
When/if some oil is squeezed out of a lifter it will take a second or two after start to refill with oil...hence the tap
Older/worn lifters can have the oil squeezed out easier then new tight lifters...but new lifters may or may not be better than this very very slight issue..
This is a source reference. Confirm exact model applicability in the original material.
