Strange Knocking Noise

mer500sel

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My 1993 500sel had the check engine light come on recently, so I went directly to the shop.
After a diagnostic Scan, I was told it's in the timing, however, when the chains were exposed it turned out NOT to be the problem.
Regardless, when the service tech had me start the car so he could listen to the knock, the knock became a bang, bang, bang and increased with revs.
I shut the car off and even the technician said there was a problem somewhere inside, yet everything looks, feels, tests fine. When we started the car after about 3 hours, the noise disappeared and we cannot get the noise to return. The car starts, idles, revs perfect, and all levels are right up. I've been told it's a blower pump problem ( not ) also a cracked or broken tappet/lifter/rocker arm. ( checked and not the problem ) Anyone have a suggestion that does not cost $200 an hr to find? I'm afraid to drive it. Check Engine light is still on.
.Garage stored in the winter months. Driven from BC to Palm Springs/return.
100,000 miles. Any ideas out there?
 

teddycatkin

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W107-SL W124-220te W123-230e W201 2.0
The noise sounds like a gummed up tappet increase with revs would fit ?--it would clear itself as you say noise has gone now.
But this would not cause the engine check light -I wonder if there is more than one fault here ?
 

kth286

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Your Mercedes
E320 Coupe 95
slack timing chain because the oil pressure in the chain tensioner has drained away.

the chain will slap against the guides when this happens.

the tensioner later filled up with oil because the engine was turning over.

on my 104 engine there is a one way oil valve which stops the oil from draining back from the tensioner - perhaps yours is faulty.

The engine light came on because the timing was out with the slack chain ? and that would affect the emissions.

I assume the light in the USA cars of that generation are only for emmisions.

Were any diagnostic fault codes revealed and what were they ?
 

matteb63

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Cl 500s & CLS500 with LPG conversions
I would check the Tensioner is in good condition...If it is jamming,sticking & or clogged it can cause erratic problems with the chain slapping..increasing with revs and occassionally working fine! As already suggested in this thread the engine light may be emanating from else where
 

Alex Crow

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Your Mercedes
W169, W124, w202, W203, KTM 250 EXC, VW T25 camper and a Polo in a pear tree
a diagnostic scan revealed cam timing faults? possible. also possible is a broken chain guide rail on these 119 engines. i have replaced a few and be warned, if a broken rail gets caught up between the chain and a sprocket/gear it could cause much damage.

also comments regarding chain tensioner problems are valid, chain slap can be very noisey and even break those plastic rails.
 
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mer500sel

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Full Scan turned up 17 faults, because the banging resulted in " max retardation " thus setting off all the sensors.
Slow process checking them all, but so far no problems.
Could the oil pump lose pressure for a moment through a piece of carbon falling off a piston and temporarily blocking the filter?
I was told the resulting noise would sound like a Rod about to be thrown.
This is the strangest experience I've ever had with a car, so me thinks once fixed, I'll give up the class comfort for practical operation.
 

meanie

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Is it possible that the noise you heard was unburnt fuel igniting in the cat/exhaust system?
Numerous faults could cause this including low compression, faulty coil, sender unit, wiring etc.
 

OlafMaxwell

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W210 E320 CDI Estate
Alexander Patient raised a point about the timing chain and tensioner. I am aware of this too and knowing the mileage and also the known problems if it were mine I would replace the chain and tensioner.
 
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mer500sel

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Well, after all is said and done, it appears there was a recall on the oil pump due to a faulty pump nozzle. It turns out the screen gets plugged periodically, and stops the flow of oil to the Cam oilers and Timing Chain. Albeit for just a few seconds, the banging causes the Tensioer to heat and go slack. Regardless, Tensioner, oilers, and while apart, the Cam adjuster need replacing.
After all is said and done....$2000 Cdn. Thanks for all your assistance. I'll stay in touch.
 
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mer500sel

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Sorry, forgot to mention the guides will be replaced also. Chain is like new, so mechanic says it's fine.
 
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mer500sel

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Back again. Still haven't got my car back from the timing issue. I'm beginning to think that Mercedes mechanics make **** up as they go along so they can try and justify their jobs.
Regardless, after the whole timing assembly was put back together, the instrument cluster doesn't work. Extensive ( expensive ) testing shows power to, but not out of the circuit board. Worked fine when it went in. Any suggestions other than try to purchase a new one? Did the mechanic screw up? Forgot a connection maybe?
 

television

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2002 SL500, 216 CL500, all fully loaded
I cannot see how this could mess up the cluster, unless he shorted or grounded any live sensors on the engine that go directly to the cluster,,if you open the cluster up,,with a continuity tester the PCB tracks can be checked out. I may have some info on these clusters but not today
 
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mer500sel

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Reset

The mechanic tells me the reset doesn't work on the instrument cluster, that is why it has to be replaced.
Do you, or does anyone know how to reset?
 


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