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
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!
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.