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Registered 2003 SLK230
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52 Posts
Discussion Starter #1
2003 SLK 230 41,000 total miles since new.

I have posed on this previously (2011-) since buying my car (showroom new condition throughout) with 38,XXX miles, but never got a definitive answer.

When I start my car after it has sat for a while- 3 days or more generally, the engine starts silently, and about 1.5sec after start I hear what I believe is timing chain slap, then a second or so later it goes silent again, and stays silent for as long as I drive the car, or even if I shut-down and re-start in 3 or so days or less.

I have been told various things:
1) Your engine is shot, and you need a new one.
2) Your chain is stretched and you need a new one.
3) Your tensioner is shot and need a new one.
4) Your tensioner AND all chain guides are shot and need to be replaced.
5) Your valve lifters are noisy because they drain due to worn out lifters or or clogged with dirty oil/sludge/carbon.

All suggesting 1-4 say DO NOT DRIVE the car until it's repaired as the chain will slip/snap and destroy the engine. Suggestion 5 says just drive the car with additive to clean the engine tappets out and use better quality oil to prevent re-occurrence. It's had Mobil 1 Euro Formula since new, begging the question of what is better if Mobil 1 clogs lifters in 40k miles?

Looking into the oil filler, the engine looks almost new-clean, with no real amber color even.

I've done extensive searches here and elsewhere with no real answer, but a search of this Forum (and elsewhere) has SEVERAL complaints of precisely the same symptoms. Some have changed their chain tensioners with no improvement.

Given that my car has only 41,000mi on it (and when I bought it at under 39,000mi it already HAD the noise) I find it hard to believe that my engine is worn out. It received regular Mobil 1 oil changes every 5000mi since new.

I also find it hard to believe my chain and chain guides are stretched/worn out in less than 40,000mi.

While the tensioner should still be OK, it is cheap so I bought one to try (but have not yet tried to install it).

I've been wrenching for 50 years, and I do not believe I am hearing valve noise, and a very experienced 25 year BMW/MB factory trained tech says it's definitely chain noise. He says the final tensioner position keeps the chain quiet for a second or so until it's pushed back despite the ratchet design allowing chain clatter until the new oil pressure reaches in inside 3 seconds, after which it's silent and the engine runs flawlessly (except supercharger noise I've also posted about).

It appears that the tensioner cannot be accessed with the super charger in place, being located above the alternator, and below the S/C on the right fwd side of the engine, so Super Charger removal is needed to access the chain tensioner. I got a link to Pelican rremoving the earlier M72 supercharger, but my 2003 has the Eaton M45 w/o a clutch drive, so that procedure may be slightly different (?)

I would pull the S/C and replace the plastic drive disk to see if that gets rid of the S/C "rattle", but if I don't have to remove the whole S/C to do the chain tensioner, I can alternately just remove the snout assembly to access the disk I understand, but removing and disassembling the S/C may tell me more about the condition of my S/C, but like the chain, it shouldn't be bad at 40k miles, except perhaps for the disk.

I am FINALLY going to attempt a solution because I really hesitate to drive/enjoy my car with these noises, and have only driven it a thousand or so miles since getting it home after purchase (a 1500mi drive from where I bought it). It's NUTS to own a car and not drive it, and at my age I would like to use it a bit before turning in my keys.

So, bottom line:

1) Has anyone here removed the tensioner in our cars, and did it necessitate S/C removal first?
I found these references so far: 1998 Mercedes SLK 230 Head gasket removal & replacement and
https://www.youtube.com/watch?v=XsEcUpvoFlk )
2) Has anyone (maybe some of the people that cured this problem) succeeded in getting rid of the noise I describe in the Cold Start (after sitting several days) Noise, and if so, HOW?
3) Any other suggestions/opinions welcome, of course!

Bob

BTW, I have been asked why I was dumb enough to buy the car if it had chain noise. Fair question. When I viewed and bought the car I now assume they had driven it w/in 3 days of when I test-drove it, so the chain was perfectly quiet on a few test drives. It didn't reveal itself until after my 1500mi drive home from where I purchased it, I let it sit several days and first heard it. But I assume it was already these at 38k when I bought it, but it didn't make the noise for me.
 

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Registered 2005 SLK55 AMG
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509 Posts
Wow, I don't have any experience with MB timing chain tensioners and guides but my big twin experience reminds me that they were originally spring loaded which caused engine failure due to being over tensioned by too heavy of springs causing the shoes to wear prematurely which clogged oil passages and metal to metal contact and eventual catastrophic engine failure if not addressed. To correct the problem Harley went to hydraulic loaded spring tensioners that used engine oil pressure.

Based on your description of the issue I would ask "are MB chain tensioners on your vehicle loaded hydraulically?" if they are that would explain why the noise is only evident for a few seconds and only after the car has sat for some time, your tensioner oil may be draining back over time and taking a bit to pump up when the vehicle is started and if that's the issue it's probably not as big a problem as you may think but again I don't know MB's method for loading the tensioners but I'm sure someone on here does.

Good luck.
 

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Registered 2003 SLK230
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52 Posts
Discussion Starter #4
They are both.

They have a coil spring inside, a plunger piston driven in by oil pressure.

They also have a way to only allow he plunger/piston to go in, but not retract (You have to push them through all the way and re-insert them from the outside).
 

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Registered 2003 SLK230
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52 Posts
Discussion Starter #6
Nope- Doesn't sound like that at all, actually.

It starts perfectly quiet and a tad later makes the chain noise for about 1-1.5 seconds, then is absolutely silent.

Generally flat lifters are noisy from the git-go at start, THEN get quiet.

Mine is quiet initially, then noisy for a second or so, then quiet again, all at once. Most tappets don't all go quiet all at once in my experience, and my noise starts to volume all at once, then disappears instantly a send or so later.

The tensioner SHOULD have a mechanical ratchet feature so it cannot retract after it moves out to take up chain wear with time. My tech told me he thinks the ratchet is not working properly, allowing the tensioner to be pushed back against spring pressure alone, so depends on oil pressure to keep pressure on the plunger.

This is slightly different than the one on our SLKs in that the only way to reset it is to remove the top plug and re-insert the plunger in from the outside-it should not be possible to push it back by removing the ratchet pawl, but for illustration, the video is OK to show the click-ratchet principle.


I have no idea if this is why my noise happens until oil pressure extends it or not, but I am fairly certain that it's not tappet noise. I didn't say 100% positive, but rather fairly certain. It's hard to record mechanical engine noises and have them reproduce properly, of course.

I just spent 30 min looking for Google results with "Noisy timing chain at start-up".

Hey guys
I have a Audi A4, 2005 B7
When from a cold start I get this annoying startup rattle for 1-2 seconds then it's gone. Engine is very quiet after this initial rattle. Car drives fine etc.
As I am aware this is a widespread problem but nobody has a definitive answer to solve this.

I have been driving like this for 2 years now.

We had the engine open the other day and there is no indication of wear or anything. Engine looks super clean.




I can definitively say the problem is that the oil used to keep the hydraulic lifters or a timing chain tensioner adjusted is bleeding out when it sits parked for long enough.

Whether that is happening because the lifters or a chain tensioner are worn out or because something like a oil filter drain-back check valve is not working or present in the installed filter, I'm afraid I can only speculate on. One thing really don't know is what age that starts to happen, or if it happened with brand new cars still on the lot.

I've certainly heard the same thing from many modern VW/Audi engines and professionally I consider it normal and harmless, although I find their 4 cylinder engines to be absurdly noisy in general and find that startup noise and general engine noise unacceptable personally. All the ones I see are at least a few years used, near 100k on them, and are still noisy even after the startup rattle goes away. If a car of mine made noise like that, I'd go to almost any length to fix it because it isn't "right" even though I do honestly believe its not harming anything. It seems like they all do it.

Getting back to the point, I would start by ensuring that a correct oil and filter combination is used. Absolutely synthetic oil, probably 0w40 weight, and a dealer or OEM aftermarket filter from a VW/Audi specialist (would probably also trust a Mobil1 filter). If that's all in line, I might experiment with using a heavier oil that brings up the low number to a 5w40 or 10w40. I would be thinking about replacing lifters or chain tensioners next, but would certainly spend a lot of effort researching both the lubrication system's technical data for any design flaws and forum people's experiences with solving the problem first. If I came up with nothing new in that research, I'd probably shotgun chain tensioners in it and see what happens.
 

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Registered 1999 SLK230
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204 Posts
I would look at oil weight for your climate,

if it is oil leakdown as it appears you are suggesting, a heavier oil in a warmer climate may give you a different result.

Down hear i use a heavier oil as my issues are at the top end (hot) of the oils protection range, with little need for the really cold startup protection.

It might be worth an oil change to see the effect?

Something easy to start with.

The other thing to look at, and not sure best way to do on our 230's is to time oil pressure build up just to confirm your theory that the noise stops as the oil pressure builds to a certain point.

Cheers from down under
 

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Registered 2003 SLK230
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52 Posts
Discussion Starter #8
I am using the specified Mobil 1 grade, but you're right that thicker oil may prevent the tensioner from going flat, though strangely it is silent upon engine start (one would think that would be the most flat, though maybe it takes a second to push the tensioner back in upon start).

It is never more than 20deg C when I start the car now that I am in a northern latitude, and the time-to-noise seems about the same as when I lived where start temp was often 33deg or so.

There must be an oil pressure sensor into which I can screw a mechanical gauge to check the time-to-pressurize on the engine.

I am just surprised that this could happen with a spring-loaded ratcheting tensioner IF the ratchet device is working properly (since the ratchet gradations are quite small) unless my tensioner is defective. Several other SLK owners appear to have the same problem (based on my searches) and I was hoping to maybe find one of them who'd solved the problem and hear the solution.

As I mentioned, I bought a new tensioner, but need to remove the supercharger to get at where the tensioner is located. I plan to do that soon because my supercharger is very noisy at idle speed, which from web-searches appears to be a plastic coupler disk that has worn, allowing some backlash in the drive (I hope). I will replace the tensioner as a matter of course when I pull the S/C.

I am just surprised that I have these two problems at such a low, verified mileage. Under 42,000mi shouldn't be enough to have chain wear and S/C problems in my mind.

Bob

Thanks,
Bob
 

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Registered 2002 SLK 230 R170
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355 Posts
Suggestions for Problem

I also have an R170 230k 2002 65k miles.
I had exactly the same problem - Start engine after left it for 2-3 days, previously had a run where engine was well up to temperature.
Result a Rattle from the engine after 2-3secs lasting 1-2secs.

If anyone is interested I have put a Page on my Site with .PDF files you can Download from WIS/ASRA showing the two Non-Return Valves.
https://slk-links.neocities.org/nonreturn1.html


My Indy said either Oil Flow back from Valves via Filter Body (Valve Ratle) or Chain Reservoir (chain Rattle). Both have Non-Return Valves.
On Balance he said most litely Filter Body.


:grin: However I had the Oil changed for a Quality Synthetic Oil 10W 40 Grade and the problem went away. :grin:

I view it as a temporary fix though. If ever I have to have work done in that area I will get it done.

Mike

 

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Premium Member 2005 SLK55 AMG; 2005 SLK350
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5,048 Posts
The camshaft adjuster is known to make noise, purely a cosmetic issue. Disconnect the electrical connector on the camshaft adjustment during your next cold start to rule it out.
 

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Registered 2003 SLK230
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52 Posts
Discussion Starter #12
The camshaft adjuster is known to make noise, purely a cosmetic issue. Disconnect the electrical connector on the camshaft adjustment during your next cold start to rule it out.
Interesting.

Have you heard this malady, and did it sound like chain noise to you?

I will definitely do this before my next start.

I don't have a workshop manual for the car, and though I did a search, I am not sure I found a suitable diagram for the electric portion of the variable camshaft showing the solenoid positions for the SLK.

Is there a diagram you might point me to?

I ordered a collection WIS CD Roms but have not received them yet-

BTW, just found these threads using a Google search rather than forum searches:
(I should have tried that before)
http://www.benzworld.org/forums/r170-slk-class/1607461-rattle-start-up.html
http://forums.mbclub.co.uk/threads/cold-start-engine-rattle-on-new-slk230.3131/
https://mercedesforum.com/forum/mercedes-slk-class-14/slk-230-engine-noise-39572/


Thanks,
Bob

Is the problem with the mechanism that the hot oil in the supply plumbing drains back when the car sits for a few days?
Odd that it's silent for a second or two after a start. Is that because the VVT mechanism remains filled with oil from its last run, but it takes a second for the "new" pressurized oil to reach and replace what is lost in the first seconds of operation following start?
 

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So, let's figure out what is going on?

Not sure if this thread has stopped but there is no conclusion so I think it needs waking up.

My SLK 230K (2001) with 40k miles has just started making this rattling noise on start-up after not being used for a few days. IF I turn it off and start it up again a short while later then there is no noise. The noise appears to come from the front of the engine but it vibrates all over the place so it is difficult to identify its exact source. I had a full service 3 months ago and there were no problems then. I verified that the lubricant was synthetic and I have used this garage for many years so they know my face and how pedantic I can be! We are in the mid-summer and it is hot so that may be a factor as I bought the car in January - maybe it will fix itself when the temperature drops? I doubt it!

Is removing the supercharger a big deal? If not then I might just remove the chain tensioner and give it a good clean to see if it fixes the problem.

I may go back to the garage and have them take a listen... I will report on my findings.
 

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Registered 2003 SLK230
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52 Posts
Discussion Starter #15
Not sure if this thread has stopped but there is no conclusion so I think it needs waking up.

My SLK 230K (2001) with 40k miles has just started making this rattling noise on start-up after not being used for a few days. IF I turn it off and start it up again a short while later then there is no noise. The noise appears to come from the front of the engine but it vibrates all over the place so it is difficult to identify its exact source. I had a full service 3 months ago and there were no problems then. I verified that the lubricant was synthetic and I have used this garage for many years so they know my face and how pedantic I can be! We are in the mid-summer and it is hot so that may be a factor as I bought the car in January - maybe it will fix itself when the temperature drops? I doubt it!

Is removing the supercharger a big deal? If not then I might just remove the chain tensioner and give it a good clean to see if it fixes the problem.

I may go back to the garage and have them take a listen... I will report on my findings.
I can tell you that mine (44k miles since new) STILL does this after I:

1) Removed the S/C (Easy Peasy) and disassembled it (replacing the coupling disk and oil), and
2) Replaced the tensioner with a brand new unit.

NO CHANGE at all.

I also tried adding an oil thickener ("conditioner") as an experiment to see if it would reduce oil-drainback that might be allowing the tensioner or VVT to be dry at start-up with no change.

I might note that after sitting a few days, the first start results in NO NOISE initially, but approx 2 sec AFTER start-up I get the rattle sound, and it stays for maybe 2 seconds, and is then quiet for as long as I drive the car, up to even leaving the car for maybe 2-3 days undriven.

After several days, it will make the noise again on startup.

No resolution so far.

I might add that I just changed the oil and instead of Mobil 0-40 Euro, I used LubriMoly 10w-40 semi synthetic with moly already mixed in the oil (the oil is fairly black out of the jug). I must say the engine itself is considerably quiter with this oil than with Mobil 1, not that it was noisy before.

I have already been lectured by some that I just violated MB rules by not using a specified oil and that the engine will now self-destruct because of it (I guess MB engines are so fragile that without special oil to make up for their poor quality they will destroy themselves using unapproved oils), so no need to lecture me. It was just a comment.

Even LiquiMoly additive to the Mobil 1 Euro in my C320 Wagon quieted that engine (It has 89k miles on it). Good stuff IMO.
 
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