Rattling noise on idle ('91 300 D Turbo)

One morning my `91 300 D Turbo (290K Km / 180 K miles) suddenly developed a terrible rattling noise on idle. The rattling disappears completely if the
rpm are raised to about 1000 and appear again on idle after that. It's sounds like the noise come from the front side of the engine. My guess was that it is the timing chain. However, I thing the chain starts to make noise more gradually, not from one day to the next. Therefore I thought that may be the timing chain tensioner was broken and I replaced with a new one, filled with oil as it was described in the manual. However, nothing changes.
Could it be that the sound comes not from the chain but something else or I should go directly for a new chain?
Thanks.
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oilchange oilchange oilchange oilchange oilchange oilchange oilchange oilchange
yes, oilchange. oilchange every 3000 kilometers.
but for this rattle do oilchange every 500 km 3 times.
dont forget the oilfilter - chance every time.
use a good synthetic oil on the last 500 km change
your engine is most likely dirty inside of it
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The oil is changed on the recommended intervals (10 000 km) or shorter allays together with the oil filter. I am using fully synthetic 0W40 over the last 60 000 km. The last oil and filter change was 2000 km ago. So, I could not agree with you. However, thank you for your opinion.
Dimi

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broken motor mount
the case, minus a few cans!
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My 190D 2.5 had a rattle like you mention. Just between 1000-1200 rpm. Annoying. I kept doing oilchanges as I believed my engine was dirty from prior owner. No more rattle after many oilchanges a year ago. Runs fine now.
If you dont do oilchanges yourself make sure you SEE it done you never know what those mechanics do. Maybe change oil yourself. And filter. Takes 15 minutes.
Theese engines are made to run and run and run.
Maybe add some diesel fuel treetment to your tank to clean your injectors. Do this very often.
Once your engine dont rattle then treament follows regularly.
Regards Niels
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Could it be that you mean the knocking noise that some times comes from the hydraulic valve lifters? If yes, it is clearly not my case. I know the sound of knocking lifters very well. My engine rattles and clatters much terribly.
However, I think that 60 000 km with regular oil change intervals using the best fully synthetic oils on the German market and only MB OEM oil filters, should prevent an excessive dirt deposition. Additionally the engine was flushed two times with engine flush and due to different reasons the oil was changed several times on very short intervals (500 to 2000 km). And yes, after some bad experience with the workshops years ago, I always do the routine maintains (all fluids and filter changes etc.) myself.

This is a good point. I have a diesel fuel treatment in the tank added ~1000 km ago (they claim that it should be active at least 2000 km) but will not harm to add some more. I can not exclude the injectors as a source of the rattling noise. The noise is to loud to localize it correctly.
Thanks
Dimi
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Your description of the noise, rattling is difficult to interpret. Does the noise increase in intensity with increased rpm or just frequency? Does the engine shake? Does it do it all the time, or after a cold start, or???
--

73
Hank WD5JFR
"Dimi" < snipped-for-privacy@nospam.noharm.ipk-gatersleben.de> wrote in message
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The noise level do not increase with the increasing rpm, just the frequency increase but only up to 900-1000 rpm. At higher rpm the engine sounds absolutely normal. The rattling noise is permanent at idle rpm, regardless the temperature of engine and the ambient temperature. I do not see an excessive shaking of the engine.
Dimi

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sounds just like what i had i'd say lifters or injectors
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On 2004-12-21 09:14:30 -0800, "Dimi"

Get a piece of hose and a screwdriver, move around the engine while it's running and listen with the hose. Locate where the noise is actually coming from first.
Could be serpentine belt tensioner, or alternator or waterpump most likely ...
Marty
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I had a similar problem on my 300E. It was caused by a worn out bushing at the top of the belt damper.
The damper looks like a small shock absorber, and only of the top of it is visible unless you stick your head in there and look closely. In my case. the top of the damper was visibly loose and rattling/knocking... mostly when I put it in gear at an idle.
said:

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I know what you mean - the small damper on the belt tensioner. It was replaced by me a year ago but I will check it. Thanks for the hint.
Dimi
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It is not that damper... it is your tensioner pulley... change it... only $30. Easy to tell... the damper rattles as you touch it...
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It was the crankshaft belt pulley. One of its bolts was broken, one was fallen down and all of the rest were loose. How this could happend? A week ago the car was in the workshop for A/C job. What should I think?
Dimi

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oh dear - a careless mechanic. mention it too the mechanic and try to make a joke of it and ask for a free oilchange
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I do not think that I will go to this workshop again even for an oil change. After two visits for several days each, my A/C is still empty. Every time they said that now the A/C is OK.
I case that some one from the region reads this - Autohaus Borgdorf GmbH (Mercedes-Benz Dealer), 06484 Quedlinburg, Germany. NOT Recommended!
Dimi

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