Want to see if anyone else is having this problem with their C300 engine. When I start it after it has been fully warmed up and sat for a couple hours it makes a knocking noise that goes away after about 2 seconds. I've never heard anything like this before, and when I mentioned it to the dealer for the A service, they couldn't duplicate the problem. I don't think it is actually engine knock, because the sound slows down and fades away after it is started.

 

I just bought it yesterday from the local Porsche dealership and when it was warmed up and let sit for approx 10 min it knocked from what seemed to be the bottom end and quickly faded away. Sounds like once the oil pressure builds it goes away but I don't know. I'm a shade tree mechanic but this car has me scratching my head (First ever import) anyway the Porsche dealer said it was good to go.... Oh well its under warranty

 

I took my 08 C300 to the shop last month for the same thing. Anytime I crank up, there is a knock for about 2-3 seconds, then goes away. Only makes the noise if the car sits for an hour. So it could be a lubrication thing.

The tech could not duplicate. But it is getting worse, and the shifting is getting harder and delayed.

 

Call your dealer and see if the C300 6 cylinder has a hydraulic timing chain tensioner. It may have malfunctioned if it does.

I know the 4 cylinder engine in my C230 coupe is completely different than your 6 cylinders, but I had a similar issue with mine just recently. My timing chain tensioner normally rattles for about 2or3 seconds on cold start, but fills with oil, moves to the chain and stays quiet until after it sits an hour or so.

But not too long ago, it was like the tensioner wasn't getting oil and it would sit and rattle on startup, whether it was cold or warm. Then, just a suddenly as it had started, the condition cleared and no more noise.

As a precaution, I had my friend, who is my mechanic, change mine out anyway.

 

I have taken my C300 in twice for this condition, knock at startup. Mentioned the Oil backflow preventer and the tensioner you mentioned. The car came back "no problems found, could not duplicate problem." The service tech then privately mentioned to me that he has the same problem.

If so many people are having this problem, why can it not be considered a Known Condition and a resolution be offered instead of denying there is a problem?

 

If the tensioner has a bleed down valve, then this could be the problem. Usually nothing to worry about. But if you are under warranty, then have them start the car when it is cold. Have someone else start it and you and manager stand outside to hear it. I would pop the hood and make sure they didn't warm the engine before you get there. Been there before with a Datsun. They just didn't want to do the job and fix it. But after 2 months they got tired of me and put new parts in it.
Dann

 

I have an 04 C230 K and it has done it from day one. When It was under warranty they told me it was normal for these cars. I said ok. I knew the car had plenty of oil and I did my own regular oil changes so I know it wasn't low. It still does it to this day and now I have 73K on it.

 

That kind of a galuping noise is normal to all 272 and 273 engine. I have had a 06 E350, 07 E350, 06 ML350 and a 09 ML350. They all make that noise. You can not fix it. It is a normal characteristic of that engine!

 

i have a 09 c300 with 12k and it does the same thing as mentioned above. does anyone know if this could possibly result in something breaking, or know someone who has had to take their car in for repair becuase of this?

 

Hello every one, we own a 07 c280 and experienced the same issue. It started since day one but I didnt pay attention until a friend made fun of our car, he said it sounds like a diesel when started up.

I found out this happens only and only when ambient air is above 78 degree farenheit and engine was well driven for couple hours.

I took it to the dealer many time and they said nothing found, finally went MZB website and wrote 'em an email complaint about it.

They referred me back to the original dealer for Dx, except this time was with 2 master tech from MB.

After few days thay replace it with oil pump and called me to inform the car was done, I asked if you heard the noise? Both said yes just a small tickin noise (LOL). I told 'em the noise is so loud you can not miss it, it sounds like some one wackin the crank with a ball pin hammerand it lasted 2 to 3 seconds.

Another week went by and finally a call came in and said the problem is identified and parts has to be order.

The technicians informed us when we picked up our cars that they are aware of the noise and they will notify us if there are any changes. According to repair order the technicians removed right cylinder head for inspection, they found discoloration on cylinder walls ( means quenched area), replaced cylinder head, gasket, spark plugs, cam position sensor, retention cam chain, and some other sensor(BMAP?), and the final phrase was " we are aware of the noise, it is normal and will not harm your engine if you continue to operate. As soon as MB find a solution we will notify you for repair"

Now this was 2 years ago and I am still waiting, I think MBZ convince you to wait for solution and eventually your engine will blow up or you will trade in for another one. Personally I think we need to sen the Inglorious Basterds to Germany to fix this problem (LOL).

Tony, HB CA