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2015 Sl400 tapping/ knocking at cold only startup.
Knocking type noise at cold start that goes away 10 seconds or so after.(2 videos of my car and the noise are lower in this thread.) Dealer says they “think” it’s the oil pump loosing pressure causing the engine to do this, but can’t guarantee that it is what’s causing the noises.
Taking car to an Indi next week as I no longer have faith in that MB dealership for a bunch of other reasons. Recently I had a timing chain tensioner replaced. (They thought that was the issue) Noise was present at that time and they “thought” that would fix it. Somehow I think I should get some if not all of my cash back, because that didn’t fix the issue so in my head the part was replaced for nothing. MB wants thousands for the oil pump install so I am hoping the Indi can confirm the oil pump is the cause or find what the cause of the knocking is and hopefully at a much lower repair bill than the dealer. I miss driving my car, but not gonna drive it until fixed. Any ideas on knocking/tapping?
15 SL 400 100k miles. Car looks almost showroom new inside and out.
Last edited by ThatsMyDawg; 08-31-2021 at 01:32 AM.
Reason: Typo
Some tapping at cold start is common. My wife's RX has done it since new. It is worse when the ambient temperature is low. Dealer says it's normal.
Is it a new noise?
DIrect injection engines tend to have noisy injectors as well. Hopefully your Indy can confirm the source.
This noise is 100% not normal, however it has done it shortly after my purchase. The noise is so loud it’s embarrassing. The last time it did it someone was outside walking by and the look they gave me when they heard the noise was worth 1000 words. I have seen plenty of SL models in person and have never heard one do this. None of my prior MB have done this either. C230, CLK430, E350, GLK, or ML. I am hoping the dealer is right about the oil pump, I just ordered it this morning. May my indi will confirm, or find something else before the install.
As mentioned, within about 15 seconds or so the noise is gone and the car sounds like a 95k car again.
I am so upset about this and I hope I can get this resolved before it turns into something else. Driving around, or restarting with warm engine has no bad noises at all FYI. I am towing the car to the indi Monday. So sad[
QUOTE=rmorin49;8405216]Some tapping at cold start is common. My wife's RX has done it since new. It is worse when the ambient temperature is low. Dealer says it's normal.
Is it a new noise?
DIrect injection engines tend to have noisy injectors as well. Hopefully your Indy can confirm the source.[/QUOTE]
Last edited by ThatsMyDawg; 11-02-2021 at 02:15 PM.
I have only had an oil change at MB dealer since I purchased the car.
From the old service slips found in storage box behind seat an the vehicle print out from MB the car was serviced regularly since build except the last year before it was sold. No records the last year. I am 3rd owner. The car has had about 5k worth of repairs since I bought it. All repairs paid for by selling dealer (non MB dealer) and my ex warranty. I can list what was fixed but I am typing via my phone and I have to pull receipts to list them. All repairs done at MB. Ex warranty not covering this noise. Long story.
Originally Posted by David2244
What grade of oil are you using and is it MB approved?
Last edited by ThatsMyDawg; 01-29-2023 at 09:02 AM.
Knocking type noise at cold start that goes away 10 seconds or so after.
Engine noises fall into one of two frequencies, either crank speed or valve train speed (1/2x RPM). Assuming you’re correct in your description, and it is knocking NOT ticking and it’s crank speed. It sounds like a rod knocking. Piston slap will be more of a hollow sound. Plus the engine probably would run rough or trigger a CE light. This is definitely NOT normal. (Or at least what I would consider normal)
Does the car sit outside or in a somewhat cold environment? And car runs fine otherwise?
Originally Posted by ThatsMyDawg
as I no longer have faith in that MB dealership
I have read of people complaining of bottom end “knocking” and Mercedes would claim that is normal. But as David2244 mentioned, If you’re convinced you have the correct viscosity oil. Convinced all the tensioners were properly replaced. And convinced knocking is truly from the bottom of the engine. I honestly would consider inspecting the bottom end of that engine, especially if it’s that loud. Oil pump pressure can be easily verified without dropping the oil pan. There should be a port right under the oil filter you can tap a mechanical gauge into. (See below) And if it has somehow failed (rare but possible), that could also be bad news for the bottom end of that engine. 🙁
If it’s valve train sound/frequency. As rmorin49 mentioned, these engines do make quite a bit of noise. More akin to what I would describe as ticking, rattle etc…. higher frequency tone. I’m going to assume this is NOT what you’re describing.
Good Luck
Last edited by crconsulting; 08-28-2021 at 06:24 PM.
First and easiest check is to see if your engine is in the range for the timing chain tensioner check valve service bulletin.
This site and Benzworld has the information.
Sounds like they replaced the tensioners / check valves already(see below). Hopefully they did the job properly. 😟
But being a Mercedes dealer did the job, I would think/hope they did it properly….
Originally Posted by ThatsMyDawg
Recently I had a timing chain tensioner replaced. (They thought that was the issue) Noise was present at that time and they “thought” that would fix it. Because that didn’t fix the issue so in my head the part was replaced for nothing. .
Last edited by crconsulting; 08-28-2021 at 08:41 PM.
Well I guess I will have to search, but I would think that MB would have mentioned that if my car was on the list considering my car has been at MB for 45 days!
Originally Posted by chassis
First and easiest check is to see if your engine is in the range for the timing chain tensioner check valve service bulletin.
It is still summertime now, so warm. It sits in my driveway when it is at home. Outside of this knock issue and the shocks issue the car runs without issue with no error codes, dash lights, or ground fluids. Looking at the old service receipts (pre me) and carfax info it is only been owned in MD, PA and DE. Yes PA can get real snow sometimes, but I don't know what the weather was when it was in PA over the last 6 years..
Here is the thing about the noise it is more knock than tap, but I think I have a memory of a tap before, but not sure. If anyone can easily post a video please reach out to me and I can send you a video of the noise for you to post. I do not belong to any hosting sites for me to post them. The vid is only a few seconds. I have two.
Let me do a recap here and then post what work was done since I am on my computer now and not my phone.-----
Purchased car from Non MB dealer, but it is a big name brand chain. Heard this tapping/knocking on test drive but sales person assured me since I was getting an ex warranty plus their dealer had its own 3 month warranty on top of that I would have no worries for getting the issues resolved. Wrong! (my mistake, I should have got that in writing)
Same week of purchase, or within 10 days I took the car to MB for an oil change as I do with each MB car I purchase. I always go within 2 weeks. While at MB the dealer pointed out a ton of issues they found during their normal vehicle safety checks. I knew of none of these issues except a shock type issue because car didn't sound/feel as smooth as it should be while going over bumps and also had the knock sound at cold star. Remember, after warm the knock sound is gone. I had no oil spots on ground, no oil smells, no smoke, no nothing...
MB pointed of the following......
Secondary timing chain tensioner not holding tension.
Internal failure front shock right
Internal failure strut right
Oil pump not holding pressor at cold start up (said they can't say for sure say this is the cause of the knocking and it may not fix the knock, but it “should”. May find other damage when tearing down, etc. They say.
Flex disk excessive dry rot
Front cam cover leaking-reseal cylinder head front cover
I can't find the papers yet, but lower front control arm was bad as well.
Every issue was repaired at MB and paid for by my selling dealer (no longer replies to my emails by the way) or the ex warranty (never buying 3rd party ex warranty again, only buying them from MB) Ex warranty advised that they are not covering the shocks and also want the engine town down with pics, before sending a person out to confirm my oil pump damage. (Independent inspection of damage) The dealer and `I do not think thats a good idea because after the 20 hours or whatever of tear down the ex warranty can then deny the claim and I am stuck with the labor bill, when I likely will wait some before starting those repairs, however I won’t be driving the car. I have an SUV as well. Until yesterday I have not spent a dime on repairs. I ordered my two front shocks and the oil pump so the Indy would have them ready if needed.
Oh, one last gift from ex warranty company. They got mad because I said I wasn’t going to do the tear down now unless they will cover the fix. I said I would take it to another shop. He then told me “If you drive the car even 1 mile it will jeopardize this coverage and future claims, because you are driving with a known issue.” I then told him I was not driving and having it towed. He acted like he was shocked that I could have it towed and not have to drive it.
I am having the car towed out of the MB dealers lot next Monday straight to the indi.
Originally Posted by crconsulting
Engine noises fall into one of two frequencies, either crank speed or valve train speed (1/2x RPM). Assuming you’re correct in your description, and it is knocking NOT ticking and it’s crank speed. It sounds like a rod knocking. Piston slap will be more of a hollow sound. Plus the engine probably would run rough or trigger a CE light. This is definitely NOT normal. (Or at least what I would consider normal)
Does the car sit outside or in a somewhat cold environment? And car runs fine otherwise?
I have read of people complaining of bottom end “knocking” and Mercedes would claim that is normal. But as David2244 mentioned, If you’re convinced you have the correct viscosity oil. Convinced all the tensioners were properly replaced. And convinced knocking is truly from the bottom of the engine. I honestly would consider inspecting the bottom end of that engine, especially if it’s that loud. Oil pump pressure can be easily verified without dropping the oil pan. There should be a port right under the oil filter you can tap a mechanical gauge into. (See below) And if it has somehow failed (rare but possible), that could also be bad news for the bottom end of that engine. 🙁
If it’s valve train sound/frequency. As rmorin49 mentioned, these engines do make quite a bit of noise. More akin to what I would describe as ticking, rattle etc…. higher frequency tone. I’m going to assume this is NOT what you’re describing.
Good Luck
Last edited by ThatsMyDawg; 01-29-2023 at 09:03 AM.
Reason: Typos
If the oil pump is marginal, I wouldn't wait to have things fixed as it's only going to get worse, possibly MUCH worse. Yes, telling you that you have to take the risk on a 20 hour teardown before they tell you if they're paying for the repairs is a classic extended warranty game.
I guess if I were in your shoes I would be looking around for a reputable MB independent mechanic who would take the extended warranty - logic being that their hourly rate will likely be much less than the dealer, so even if you're stuck with the teardown labor, it'll be less.
Good luck, and please keep us updated on how things transpire.
Why on earth do people buy a car with a known issue and feel the need to keep it when the issue gets bigger. If you have an engine issue due to lack of oil, that car is DONE. It’s a 100k mile paperweight unless you are ready to spend thousands to repair it, lots of thousands. The knock was why owner number two likely dumped the car.
Research your state laws for return if you ever get stuck in this situation. Time is of the essence and I don’t see a good out for this person. This car needs a rebuild of the engine. Or they can forever know the bottom end, lifters, timing chain, etc all have a shortened and unreliable life ahead. The difference between the check valve noise (which I have personally done the repair) and a knock are miles apart and that diagnosis was crap.
rule one, warranties almost never cover a preexisting issue, (hence wait times for use). Buy an exclusionary policy and have your parts covered. Tear down is always on the customer, but never really when the shop correctly diagnoses a car and the repair is valid.
rule two. Never buy anything that is broken that you expect someone else to fix for free.
rule three. Pray you have a mechanic that is not just an Indy but a friend, who can tell you when you are wrong and not steal your money. This Indy hopefully tells this guy to sell the car before taking his money for repairs to help the engine for a few miles.
All of this is moot if the person paid 5k for this car in this condition having budgeted an additional ten-fifteen thousand for the repairs and engine.
I made a mistake and is why I am on this site looking for help.
I heard a noise that lasted 10 seconds literally and I could not reproduce the sound. (Later I understood that is was only at cold start) I went to the selling dealer the same week as purchase which began this process of finding what is wrong.
Selling dealer and ex warranty have paid for what was found so far except the shocks. They have not said they won’t pay for a new oil pump, they just want a bunch of hoops jumped through first to confirm what the issue is, etc. They may, or may not pay.
It doesn’t make me feel any better to read “why would people”. I have already learned a lesson that I have never had to learn before. I got too excited about my dream car.
I am human and made a mistake. I am sorry. I appreciate the ideas and suggestions.
Originally Posted by Baltistyle
Why on earth do people buy a car with a known issue and feel the need to keep it when the issue gets bigger. If you have an engine issue due to lack of oil, that car is DONE. It’s a 100k mile paperweight unless you are ready to spend thousands to repair it, lots of thousands. The knock was why owner number two likely dumped the car.
Research your state laws for return if you ever get stuck in this situation. Time is of the essence and I don’t see a good out for this person. This car needs a rebuild of the engine. Or they can forever know the bottom end, lifters, timing chain, etc all have a shortened and unreliable life ahead. The difference between the check valve noise (which I have personally done the repair) and a knock are miles apart and that diagnosis was crap.
rule one, warranties almost never cover a preexisting issue, (hence wait times for use). Buy an exclusionary policy and have your parts covered. Tear down is always on the customer, but never really when the shop correctly diagnoses a car and the repair is valid.
rule two. Never buy anything that is broken that you expect someone else to fix for free.
rule three. Pray you have a mechanic that is not just an Indy but a friend, who can tell you when you are wrong and not steal your money. This Indy hopefully tells this guy to sell the car before taking his money for repairs to help the engine for a few miles.
All of this is moot if the person paid 5k for this car in this condition having budgeted an additional ten-fifteen thousand for the repairs and engine.
good luck
Last edited by ThatsMyDawg; 08-29-2021 at 07:01 AM.
Not trying to make you feel bad. Nobody in this thread was giving the blunt reality. That reality is that you should likely get out now. These cars have high costs to repair and at 100k miles, often not worth large repairs that are not diy. You mentioned having bought Mb in the past, so I figured you were aware of the issues mentioned.
If indeed it is oil pressure and there is a way to measure that without removal, as stated elsewhere in the thread, I would start there. I would also look at the oil filter if it was not changed with the most recent oil change to see if there is metal in the filter. I’d also send an oil sample to blackstone so they can tell you if the engine is wearing abnormally.
fwiw. The timing check valve noise will disappear immediately after the repair, as long as both sides are done. This noise (a ticking) would come from the front lobes cam cover area, and not a knock, as would be described from the bottom, normally and can be felt even at the back of the car even in the exhaust vibration. Knocks, tings, ticks, buzzes, vibrations, wobbles, and taps are all truly separate words meaning specific things to the well trained ear.
everyone is here to help but nobody wants to see a new purchaser have a bad experience when there are easier options.
QUOTE=ThatsMyDawg;8405710]I made a mistake and is why I am on this site looking for help.
I heard a noise that lasted 10 seconds literally and I could not reproduce the sound. (Later I understood that is was only at cold start) I went to the selling dealer the same week as purchase which began this process of finding what is wrong.
Selling dealer and ex warranty have paid for what was found so far except the shocks. They have not said they won’t pay for a new oil pump, they just want a bunch of hoops jumped through first to confirm what the issue is, etc. They may, or may not pay.
It doesn’t make me feel any better to read “why would people”. I have already learned a lesson that I have never had to learn before. I got too excited about my dream car.
I am human and made a mistake. I am sorry. I appreciate the ideas and suggestions.[/QUOTE]
I have never had a problem like this with any of my prior MB or any car for that matter. It has been a lesson learned that I won’t repeat again.
MB has already confirmed that the oil pump is loosing pressure. They only thing that MB hasn’t done is confirm that by changing the oil pump it will fix the knocking issue.
For the mechanics out there, is there a reason why the oil pump would only not have pressure on cold start, but have pressure when warm the rest of the day until another cold start?
If the oil pump is bad enough to loose pressure on cold start shouldn't replacing the oil pump/fixing the pressure loss fix this issue? If it was more going on wouldnt the knock continue past the cold starts and carryon even while warm? Why does the warm start up make the issue not return? Asking from a non mechanics point of few.
Seems to me that the noise would be there all the time and not just for 10 seconds.
Thanks.
Originally Posted by Baltistyle
Not trying to make you feel bad. Nobody in this thread was giving the blunt reality. That reality is that you should likely get out now. These cars have high costs to repair and at 100k miles, often not worth large repairs that are not diy. You mentioned having bought Mb in the past, so I figured you were aware of the issues mentioned.
If indeed it is oil pressure and there is a way to measure that without removal, as stated elsewhere in the thread, I would start there. I would also look at the oil filter if it was not changed with the most recent oil change to see if there is metal in the filter. I’d also send an oil sample to blackstone so they can tell you if the engine is wearing abnormally.
fwiw. The timing check valve noise will disappear immediately after the repair, as long as both sides are done. This noise (a ticking) would come from the front lobes cam cover area, and not a knock, as would be described from the bottom, normally and can be felt even at the back of the car even in the exhaust vibration. Knocks, tings, ticks, buzzes, vibrations, wobbles, and taps are all truly separate words meaning specific things to the well trained ear.
everyone is here to help but nobody wants to see a new purchaser have a bad experience when there are easier options.
QUOTE=ThatsMyDawg;8405710]I made a mistake and is why I am on this site looking for help.
I heard a noise that lasted 10 seconds literally and I could not reproduce the sound. (Later I understood that is was only at cold start) I went to the selling dealer the same week as purchase which began this process of finding what is wrong.
Selling dealer and ex warranty have paid for what was found so far except the shocks. They have not said they won’t pay for a new oil pump, they just want a bunch of hoops jumped through first to confirm what the issue is, etc. They may, or may not pay.
It doesn’t make me feel any better to read “why would people”. I have already learned a lesson that I have never had to learn before. I got too excited about my dream car.
I am human and made a mistake. I am sorry. I appreciate the ideas and suggestions.
[/QUOTE]
Last edited by ThatsMyDawg; 08-29-2021 at 11:51 AM.
Reason: Typo
Cold oil is more viscus (thicker) harder to pump and pump discharge pressure is higher under this condition.If there is a bypass in the pump to prevent overpressure and it is opening at too low a pressure it will starve the engine of oil and would cause the noise you hear until the oil warms up and the bypass closes and pump is able to supply oil under pressure to the oiling system NOT bypassed back to the sump thereby starving the engine on cold start.
Does it sound like this? Many describe this as rattling while others knocking.
Tensioners can get loud, But you did mention they (dealer) replaced them.
Hopefully they did the job properly….
But low oil pressure at tensioners could do this too or faulty/wrong check valves.
Does it sound like this? Many describe this as rattling while others knocking.
Tensioners can get loud, But you did mention they (dealer) replaced them.
Hopefully they did the job properly….
But low oil pressure at tensioners could do this too or faulty/wrong check valves.
In addition to what I wrote above @ 5:29PM you may find the following interesting:
Mercedes M278 Engine Problems and Reliability
Early build M278 V8s had some problems with the timing chain tensioners causing a rattle on start up. The engine has a pretty complicated timing chain drive arrangement. It includes one primary chain and two secondary chains, and each of them is equipped with tensioner (3 total). If not pay attention to knocks/noise for a long time, this may lead to the replacement of the entire chain drive system together with cam adjusters. There were some reports of engine oil starvation due to the failure of the oil pump drive gear (oil pump is driven via a chain).
Is that your car?
That sounds like tensioners. But if they did them properly that “should” have gone away.
Take a look at your invoice did they do the check valves along with tensioners?
There should be part numbers on that invoice.
What are they?
08-27-2021, 09:39 PM
