Diesel knock noise? w211 220cdi

[haydar]

Hi guys

I need some help.

I've got a 220cdi w211 which has covered some 100k miles. Now when I start the car for a few seconds the engine note is perfect, but then it suddenly hardens and gets louder. It's almost as if there is a slight diesel knock.

Now over the last few months I've changed the following:-

i. New main drive pully
ii. New belt tensioner
iii. New auxiliary belt
iv. New water pump
v. New injectors
vi. New MAF
vii. New EGR valve
viii. New valve seals
ix. New turbo

I'm now kind of running out of ideas, what could be causing the problem. Once the car revs rise over about 2k rpm it all quietens down.

My question is does anyone know what could be causing the hardening of the engine note. Like I said, when the car is started for a few seconds the engine note is beautiful, but then suddenly it hardens!! Is there something that turns on at this time that can be causing this?

The cars performance is fantastic and it is noticeably quicker than other 220cdi here!!!

I'll try to record the sound tomorrow and post it onto the site.

Thanks for all advice.

 

[chelsw6]

Do you get the noise when its hot, cold, or every time you start it,

 

[greenfingers]

Are you sure it has the correct (fully synthetic?) engine oil?

 

[chelsw6]

I was thinking that if its only making a noise from cold maybe the oil on the cams is being flung off when it first starts and the oil at the bottom is not coming up then he gets the noise, when the revs rise to 2k its being forced up and when its warm the oil is thinner so would get up there more easy and flow as it should.

 

[Wezzel]

Try putting in some injector cleaner such as redex. I swear by it to stop diesel knock and as soon as I stop using it mine comes back.

The cleaner incorporates a cetane improver which helps the diesel ignite more quickly and prevent knock.

I put it in at EVERY fill up. Works out at something like £7.99 for 5 fill ups. Worth a try.

 

[haydar]

I've used my mobile to capture the sound of the engine. How do I post the sound to the forum? Also, the file is in .amr format, do I need to convert it to mp3? So so how?

Thanks for all advice.

 

[haydar]

Here is a wav file version sound.wav

This is the car starting first thing in the morning. The was was in a large garage and I was standing over the engine with the bonnet open.

The car changes note regardless of it being hot or cold, but it sounds more prevalent was cold. The oil used in the car is mobile 1 fully synthetic.

I guess my question is that the noise changes after a few seconds of startup. What could be making that happen.

Here is a wav file of the car when it's warmed up with the bonnet closed sound2.wav

 

[chelsw6]

I would look at the cams if i were you.

 

[Parrot of Doom]

Sounds rough to me, although a camera phone will always accentuate the mid-range frequencies so.

As a comparison, although I have a completely different engine, heres mine starting up:

http://homepage.ntlworld.com/tom.jeffs4/om606 engine running.wma

 

[mioba]

definately agree with earlier post, use redex, and switch to a premium fuel

 

[haydar]

Sounds rough to me, although a camera phone will always accentuate the mid-range frequencies so.

As a comparison, although I have a completely different engine, heres mine starting up:

http://homepage.ntlworld.com/tom.jeffs4/om606 engine running.wma

Link didn't seem to work?

 

[Captain Flack]

Is the a/c on. The change in sound could be the a/c compressor putting extra load on the engine a few seconds after starting, and in all honesty I don't think that it is abnormal. My C270 sounds similar.

Have you listened to any other C220's to see if they are the same?

 

[Parrot of Doom]

http://homepage.ntlworld.com/tom.jeffs4/om606 engine running.wma

 

[Captain Flack]

That sounds like a 320 as opposed to a 4 cylinder 220?

 

[Parrot of Doom]

Its an OM606 TD. I just posted it so the OP could have an idea of what a normal diesel engine may sound like.

 

[haydar]

Forgive my ignorance, but what is a OM606 TD??

 

[Parrot of Doom]

A 3.0 turbocharged straight 6 diesel Mercedes engine

 

[haydar]

OK

Took car to MB dealer today. All the mechanics gathered around to listen to the change in the engine note after the car is started. One by one different components were disconnected, such as the glow plugs switch, EGR, MAS, etc... Yet everytime the car was started, after a few seconds the engine note would change.

Putting the car on the diagnostic machine, I was there as they ran through ever test available, compression, egr, mas, boost pressure, idle speed, etc... everything checked out!! No issues at all!

They then decided the knocking noise must be coming from the timing chain. So they dismantled the head, but the chain looked OK. However they changed the timing chain tentioner, changed the hydraulic elements (lifters), resealed the injectors, put the car back together again and no joy. The car is still making the same noise.

They however observed that the inlet manifold seemed to be extremely carbonated (which may have happened when the turbo seals had leaked) and hence could have some kind of blockage. Hence tomorrow they are going to dismantle and clean this out. I believe there are some inlet valves that also may not be working properly.

Let's see what tomorrow brings.

 

[haydar]

OK

Took car to MB dealer today. All the mechanics gathered around to listen to the change in the engine note after the car is started. One by one different components were disconnected, such as the glow plugs switch, EGR, MAS, etc... Yet everytime the car was started, after a few seconds the engine note would change.

Putting the car on the diagnostic machine, I was there as they ran through ever test available, compression, egr, mas, boost pressure, idle speed, etc... everything checked out!! No issues at all!

They then decided the knocking noise must be coming from the timing chain. So they dismantled the head, but the chain looked OK. However they changed the timing chain tentioner, changed the hydraulic elements (lifters), resealed the injectors, put the car back together again and no joy. The car is still making the same noise.

They however observed that the inlet manifold seemed to be extremely carbonated (which may have happened when the turbo seals had leaked) and hence could have some kind of blockage. Hence tomorrow they are going to dismantle and clean this out. I believe there are some inlet valves that also may not be working properly.

Let's see what tomorrow brings.

 

[HelpThisDude]

I know its been almost 3years but...... I wish the Gent had updated his progress. Would have been interesting....