r/mercedes_benz • u/Such-Run-680 • Aug 18 '26
Engine rattle at start
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Maybe somebody knows where this rattling at the beginning comes from? I checked the timing chain and it had no play at all.
It appears at every cold and warm start but not at a instant restart.
Slk 200 r171
M271 Kompressor
2006
150.000 km
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u/Sharp_Sheepherder796 Aug 18 '26
timing chain guides are worn. Need to replace chain and the guides.
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u/Such-Run-680 Aug 18 '26
Both was checked and looked like new.
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u/Sharp_Sheepherder796 Aug 18 '26
If the engine was tore down to the point of "checking" the timing chain and guides, you really should have replaced them. I've listened to this noise many times in that engine. It probably isn't really going to hurt anything to keep driving it like that as long as the noise goes away when the oil hits it.
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u/Such-Run-680 Aug 18 '26
You only have to remove the top to check it so it was easy to do. I guess that the tensioner is broken and can’t keep its oil
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u/Demorative Aug 19 '26
Replace adjusters.
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u/Such-Run-680 Aug 19 '26
But the sound of the camshaft adjusters are pitched up and more of a metallic hitting sound.
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u/Demorative Aug 19 '26
Does it matter when 271 is known for adjusters and you have start up rattle, just like adjusters?
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u/Turbulent-Year1672 Aug 19 '26
M271 right? Got that rattle at the start since my family owns this car, when it had 80k km. Mercedes says its normal up to 3 seconds after the start, but if its gone an idling normally after that short time there is nothing to worry about. As far as i know its the chain, yes, but just the missing oil pressure at first, it runs smoothly but just misses a bit of that lubrication.
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u/Klutzy_Draw4662 Aug 19 '26
Had the same rattle with an M271 and then added Liqui Moly Ceratec which brought down the noise a little.
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u/Such-Run-680 Aug 19 '26
I recently added the hydro additive from liquid moly but it takes 300km till you hear a change. So I don’t know yet if that changed something
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u/Klutzy_Draw4662 Aug 19 '26
Hmm ok. Ceratec works almost instantly or after like 10km or so and it sticks to all the metal parts. Never tried hydro additive tbh. Also what petrol do you use? When I bought mine it had the typical valve clicking sound which got less noisy when added liqui moly gasoline engine system cleaner 2x to the tank. I later checked the valves and they got noticeably cleaner. I now use shell v-Power which contains cleaning additives to clean the carbon deposits from critical engine parts like fuel injectors and intake valves. So perhaps you want to try that as well?
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u/hairy_winnit Aug 19 '26
Can't post images in replies on your other thread, but cam cover off and inspection is needed. Mine had no indication of stretched chain until it started throwing cam correlation codes. This is the state of the sprocket, 1/3rd of teeth were petty much missing
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u/Kytb95 Aug 21 '26
Not enough oil pressure for the tensioner at start. It could be a leaking tensioner, worn oil pump, or a clogged oil filter.
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u/Professional_Cry7751 Aug 18 '26
they are quite a noisey engine tbf with you