Cold start noise
09-06-2021, 07:26 PM
#1
Member
Thread Starter
Cold start noise
Noticing a clacking sound on cold start. Lasts about five seconds. If I turn off the engine and start it back up, it does not return. What might this be?
09-08-2021, 04:52 AM
#2
Junior Member
I don't know the engine on your car, but usually this kind of noises relate to some sort of hydraulic device(s) that work with engine oil under pressure. They drain out when engine is stopped, and then, when it restarts, do some noise for a few seconds, until the oil pressure builds up and pressurizes them again. Most usual suspects are hydraulic tappets and chain tensioners. If the noise doesn't return until the engine has been stopped for a few hours, I would bet that is something along these lines.
Things I would check: oil level, oil type (a recent oil change could have used a thinner oil), oil mileage, oil leaks (especially if recently appeared), inspect any recent work on the engine (cambelt change, oil change, etc.). And, of course, engine codes...but this kind of issue does not, usually, appear in the codes, unless it is really severe and is causing other problems.
As for seriousness, it depends on the engine type ( I'm not talking about Mercedes engines only). On some engine types, this is almost universal (all engine specimens have it to some degree), has no pratical consequences, and requires no attention. On other types, when this appears (usually on tappets/cam followers), it is known that it will get worse, cause other problems, and must be fixed (usually by replacing the tappets). As I said, I don't know the specifics of your particular CLK350 engine type, but it shouldn't be hard to research.
Good luck, and let us know how this progresses.
DF
Things I would check: oil level, oil type (a recent oil change could have used a thinner oil), oil mileage, oil leaks (especially if recently appeared), inspect any recent work on the engine (cambelt change, oil change, etc.). And, of course, engine codes...but this kind of issue does not, usually, appear in the codes, unless it is really severe and is causing other problems.
As for seriousness, it depends on the engine type ( I'm not talking about Mercedes engines only). On some engine types, this is almost universal (all engine specimens have it to some degree), has no pratical consequences, and requires no attention. On other types, when this appears (usually on tappets/cam followers), it is known that it will get worse, cause other problems, and must be fixed (usually by replacing the tappets). As I said, I don't know the specifics of your particular CLK350 engine type, but it shouldn't be hard to research.
Good luck, and let us know how this progresses.
DF
09-08-2021, 07:51 AM
#3
Member
Thread Starter
Thanks for your response. To answer a few of your questions, the oil was changed six months ago, I have put 3000 miles on the car since then, I change it myself so the correct oil is being used. Also, I might add that this has been going on for a couple of years. It has not gotten any worse.
