I have this STRANGE noise with my 603, happens right around 1100 RPMs.
Its not injector or bearing knock.
Many times you have to gently play with the RPMs to irritate it.
Can happen in drive or park.
Car drives perfect.
BUT if your creeping in traffic at times or trodding up a parking lot it shows up.
Almost sounds like a bad belt driven accessory.
I recently replaced my Vacuum pump, a/c compressor, water pump, tensioner ,alternator, idler and fan clutch- all good!
I'm thinking its the injection pump, chain or a lifter. The sound is also like a slapping and rumbling sound - THEN it clears right up?!
Sometimes when the noise is really rock and rolling the engine runs just a bit rough - only to clear up in an instant.
Idle speed or above 1K-1100 RMPs and no issues at all.
I'm worried something could let loose at any time.
Ideas???

Mileage?

My 603 rocked around pretty really violently before I got the injectors rebuilt. I have a clack noise in mine, but I think it is lifters. How are your lifters?

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RenaissanceMan Labs: where the future is being made today.

Garage:

2017 Chevy Colorado Diesel (nanny state emissions)
2005 Volvo S40 T5 AWD, 77k
1987 Mercedes-Benz 300D turbodiesel, 4 sp auto, 156k - 28.7 mpg
1996 Tracker 4x4, 2 door, 16v, 3 sp auto. 113k - 28.6 mpg

WARNING: this post may contain dangerous free thinking.

How is your belt tensioner damper (shock)?

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Gone to the dark side

- Jeff

210K
Yes the belt shock is new too. Had the belt off for a test.
I'm not sure its a lifter issue. The noise does not seem to be in time with cam lobes.
Picture a loose crank damper balancer making that awful rumbling noise and then suddenly clears right up with a change in RPM.

How are the engine mounts? Maybe it's a resonance somewhere on the body at certain frequencies?

__________________
RenaissanceMan Labs: where the future is being made today.

Garage:

2017 Chevy Colorado Diesel (nanny state emissions)
2005 Volvo S40 T5 AWD, 77k
1987 Mercedes-Benz 300D turbodiesel, 4 sp auto, 156k - 28.7 mpg
1996 Tracker 4x4, 2 door, 16v, 3 sp auto. 113k - 28.6 mpg

WARNING: this post may contain dangerous free thinking.

Motor mounts are new too.

Along with the noise is also a kind of scraping sound.

I think I found a post about something like the 603 leaking oil into the combustion chamber, causing noise and sometimes smoke at certain times. Can't find it again.

A terrific tool for finding the source of the noise is a piece of rubber tubing about three feet long or so. Hold one end in your good ear, and CAREFULLY and SAFELY move the other end around and over the various suspect components (all the accessories run by the serpentine belt). If you cannot ID the source this way, then it is likely internal. You may be able to narrow down the source to front or back of the engine (if internal).

Another way: remove the serpentine belt and run the engine briefly to see if the noise persists or has gone away. Don't run the engine too long - the water pump is not circulating coolant and you don't want to overheat the engine.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Oil in combustion chamber cylinder one .
My 250D is smokin! - Mercedes-Benz Owners' Forums

And a bit more reading here, note there is no oil or water contamination when the head gasket weakens in this area on number one cylinder .. Only smoke eventually getting very bad with knocking on that cylinder.
Thick smoke under load after idle - Mercedes-Benz Owners' Forums

what brand belt tensioner did you install?

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

check for loose belt pulley at crankshaft,i had one that acted as you describe and did not find the source of the noise until it got worse and by then the bolt holes were worn badly.I had to replace the pulley(dealer had to get it from Germany) and all the bolts

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Red Green "This is only temporary,Unless it works!"

97 E300D 157000 miles
87 300TD ?141k? miles

I have same noise in my 87Tdt at the present time.

Do you lube your fuel with a diesel additive to reduce knocking, etc.? The original diesel fuels had lubrication in them that the injectors depended upon, but now there's none in the fuel so you need an additive in there now.

Hopefully not the case but make sure your crank pulley bolt isn't loose.

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Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k