Diesel knock noise? w211 220cdi

[Dieselman]

It sounds like combustion knock.
Try revving the engine and letting it fall to idle. If the noise stops on over-run but comes back on as the fuelling comes back on near idle, then it has to be fuel related and the mechanical side of the engine is Ok.

Try disconnecting each of the injectors in turn and see if the noise stops, if so it's a dribbling injector.

Having listened to the noise I wonder if you are being a bit too picky..

 

[haydar]

I'll ask them to give it a try. The injectors are new and the MB guys tried the disconnecting job, all seemed fine.

It's not just the noise, there seems to be a roughness to the engine too.

 

[LastMinute]

You've been to Pakistan me thinks .

No - just trying to work out the economics of Dieselman's business plan...

 

[Dieselman]

Well, I'm probably wrong but if the taxation is very high often the basic vehicle price is set very low to compensate. If the vehicle is then exported the taxation isn't levied or is refunded thus making a cheap vehicle.

I don't see why the tax wouldn't be refunded to a non Pakistan resident.

Of course I could be wrong, do you have any information that would suggest that?

It was the above scenario that made cars from Denmark the cheapest in Europe.

 

[LastMinute]

Of course I could be wrong, do you have any information that would suggest that?

No - I just needed it explaining in short words...
I see now what you're getting at - but still I can't help thinking that there must be some obstacle to doing it.

 

[Dieselman]

I can think of something, the car wouldn't be CE marked so would require an SVA test, but other than that it would work if the base price was low enough.

I also wonder if the taxation is only so high on new vehicles being imported and whether it applies to 2nd hand ones.

Just a thought..

 

[Dieselman]

How about some reverse engineering. What in the engine could be making the knocking noise? The cams were checked and all seemed fine. Hydraulic lifters have been changed. The timing chain was not changed but seemed OK, although the chain tensioner was changed. The MB guys are convinced the noise is coming from the top end and not the bottom end.

Try using a stethoscope on the different parts of the engine. This will reveal any internal rattling.

A thought just occurred, it could be an external components which then rattles through the engine block.

 

[haydar]

Mercedes imported by the single main agent are very highly priced, even more so than if you bought one and imported it yourself! I know in Europe you guys see Mercs as German taxis but in Pakistan/India, they are reserved for the very rich (or the clinically insane like me).

As for the stethoscope, the MB guys tried this. Apparently it didn't matter where they put the bloody thing near the top of the engine, they hear the knocking. However it's not lower down in the engine. Basically, nothing conclusive.

We've changed the water pump, the tensioner pulley, the guide pulleys and the main drive pulley. I guess this leaves the power steering pump and alternator? But wouldn't these be on right from startup and not kick in 2-5 seconds later???

 

[haydar]

Update:

They've cleaned the car's intake and although it is now quieter, the knocking is still there. The car is now down on power, but smoother than before, which to be honest I can live with.

The next step would be to change the drive chain and pulley, now on order.

 

[haydar]

Haydar, the noise sounds like the timing is being advanced for cold start and after a short while is retarding again.
This is normal, although I'm not saying the noise is necessarily.

Dieselman, you were absolutely right. This is normal behaviour, by chance MB guys got another 220cdi in today and it did the same thing. However it was quieter afterwards compared to mine.

I had a question though, a engine is reving at 800rpm at idle. If there is a diesel knock due to fueling, wouldn't it have to happen 800 times per minute. How could you hear it? The knocking noise I'm talking about can be heard roughly twice a second.

 

[Dieselman]

The engine is rotating at 800rpm but it's a 4 stroke engine so it only fires alternate cycles.
Mechanical components that rotate slowly are cam and valve gear and fuel pump.

If the stethoscope says there is a knock then it's mechanical, check the tappets are not stuck.

 

[haydar]

The tappets have been serviced, but I guess it's possible that one or more is faulty. Although the CAMs seemed fine to visual examination, again there could be a very tiny intolerance that's causing the noise. Not sure if there is a sure fire way to test this stuff apart from by new ones .

Know anywhere I could by a complete new head off a low mileage 220cdi

 

[fredfloggle]

STOP !
Before they wreck what is left of it - there was not much the matter with it from the start - why does everyone assume that every engine has to sound the same , they don't . If a car hasn't been thrashed for 100K miles , sometimes the worst thing someone can do is to hammer it for a bit , to "give it a good clear out" - quickest way to break the top rings .

Sure , your engine isn't the sweetest I have every heard , but you have wasted loads on achieveing nothing , possibly the only thing done that was worthwhile was to clean out the manifold - the rest was fruitless - I firmly believe in not taking engines apart unless they really need it .

To clarify , 800 knocks(at idle) a minute is down to something crank related .
400 knocks per minute is something related to cam train , or combustion related .
Each cylinder fires once every second revolution .

If you get a constant rattling noise , you have either purchased a british car , or your wife is with you .

 

[haydar]

You know you are probably right. Like I said, I'm clinically insane!

Interesting comment about the british car (which of course it is), do MB UK build in the rattle for an additional charge or is it a no cost option.

 

[fredfloggle]

Paint dropping off , failing electrics and steering that pulls in alternate directions are non-cost options , you have to pay extra for the rattle .

British ?

 

[big x]

When I was in Pakistan I seem to remember poor quality fuel and pot marked roads.Check your engine mounts, they may be transmitting noise and vibration if leaking.
The best solution would be to buy a nice smooth running petrol engine.
To recoup your costs organize a little hunting trip to the North Warizstan region and claim the bounty on Bin Ladens head Trust me that's where he is hiding out.

adam

 

[haydar]

When I was in Pakistan I seem to remember poor quality fuel and pot marked roads.Check your engine mounts, they may be transmitting noise and vibration if leaking.
The best solution would be to buy a nice smooth running petrol engine.
To recoup your costs organize a little hunting trip to the North Warizstan region and claim the bounty on Bin Ladens head Trust me that's where he is hiding out.

adam

You seem to have an excessive knowledge about Bin Ladens whereabouts Adam, or is it Bin Adam . Anyway, my bet it you'll find Bin Laden at Camp David, dining with Bush as they split the billions they've both made from the Iraq war.

When were you last in Pakistan and whereabouts in Pakistan? Yes we've still got the pot holes and poor fuel, so not so disimilar to Somerset then. .

As for North Wariztan, there was a report in the news recently about a 10 man heavily armed police petrol who stopped a bus for a routine check, but decided to let it go when they realised the passengers had more and better guns than they did. .

The Soviet/Afgan war left Pakistan with 6 million Afgan refugees! (And UK thinks it has problems with respect to people from the old Eastern Block!) There is a chance that Bin Laden is hiding amongst these people, who now thanks to the US invasion are producing heroine like it's going out of fashion, so are extremely rich and better armed than the Pakistani army.

 

[big x]

Of course the other possibility is OBL has returned to Saudi. The Bin Laden family construction business certainly have the resources to shield him.
Dubya doesn't seem that interested in catching him perhaps because any trial would expose the kickbacks paid to the Bush family over many years in the oil construction industry by the Bin Laden companies.
I visited Pakistan's North west frontier region in the late 80's on my travels through Asia.


adam

 

[haydar]

Did you travel the Karakorum Highway (the old silk route). I've driven to China, past Gilgit in the late 90s. A humbling experience to see the
Himalayas in all their glory.
What is it about Mountains that it produces very hardy people. America's got the Hillbillies, UK's got the Scots and Pakistan's got the Patans! People who believe a casual look is excuse enough to kill someone!!!! Having said that they can be the friendliest of people too, willing to move mountain to help (if you pardon the pun).
OBL and Bush have both become the boogeymen for the opposing camps. It gives lunatics on both sides the excuse to commit insane acts against each other. It's hard for us mere motals to reconcile the aquisition of a couple of trillion dollars against the lives of thousands of Americans/Europeans and hundreds of thousands of Iraqis! I guess we're just not leadship material!

 

[big x]

What is it about Mountains that it produces very hardy people. America's got the Hillbillies

The Hillbillies are a bit to inbred to be called hardy !
Try and watch the excellent film "Deliverance" by the
British director John Boorman.Anyone who has visited the Blue ridge mountains in Virginia will recognize this.
Talk about inbreeding......

adam