Here is my experience. My son's 2000 C230K has about 115m. After sitting for 3-5 days, the car would start with a tremendous death rattle. Engine would briefly sound like it was coming apart. Not just a whine or squeal or minor roughness, this was a scary metal grinding rattle. If the car was driven daily, it was fine. Besides the occasional rough start, car runs normal.

I first suspected the kompressor. Checked out fine. Then I changed the camshaft adjuster magnet. This is the hat shaped thingie at the front of the engine. No change. I then changed the timing chain tensioner. No help there either. Car still sometimes has that scary start when not driven for a few days.

So far these are the parts referred to above. Can anyone sort these out?

hydraulic cam chain tensioner
cam advance unit
cam belt tensioner
cam adjuster solenoid
cam adjuster mechanism
cam chain tensioner

Thanks

My 2001 SLK230 has done this since new. If I drive it daily, it doesn't make the noise at cold start-up. If it sits for any length of time, it makes the noise at cold start-up. I've noticed over the years that it isn't as bad after an oil change. I only use Mobil1 0-w40.

My cam adjuster was replaced a few years ago under a recall for the plug problem that cause oil wicking. It still makes the noise after sitting several days, but I've just lived with it.

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

I'd put on an oil pressure gauge and watch how long it takes oil pressure to rise. There is a chance the oil filter is draining out and it takes that long to build pressure. Some engines have an anti oil filter drain back valve, not sure if these do or not.

At least on my 97 M104 inline 6 , when the oil filter cap is removed and filter element extracted, the filter housing drains out. I'd have a hard look at how that system works to make sure it isn't leaking when the filter is installed.

If your timing chain guide rails are not worn / broken, I'd be real tempted to put something in / on the oil fed tensioner to limit how far it collapses and maybe a light compression spring. You could set if up so the chain is slightly loose without oil pressure rather than the drastically loose you have now the nose will be greatly reduced.

Many cars of other brands use a ratcheting mechanism to limit collapse but I don't know if these cars have them or not . ( apparently not due to the start up noise. )

Items 1 ,3 , 6 are the same part ( except on our engines we ahve a chain not a belt ) This is a device that maintains proper tension / take the slack out of the timing chain.

2 , 5 are the same part, they vary the intake camshaft timing relative to the crankshaft. This gives a broader flatter power band ( Rather than the engine being tuned to make power at a specific RPM , the adjuster broadens the power curve. As a side note, many intake manifolds use a long / short runner flap valve to help stretch out the power curve as well. )

4 This is a non part though in some sense the electro magnet coil and cam adjuster could be considered a solenoid system but no one in the USA is going to refer to it as such. ( Unless it as an artifact from German / English translation. )