320 CDI engine knock

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W205 C250 CDI
I have a knock from the front of a w210 320 CDI engine (2000 & 110,000 miles). Sounds like no1 cylinder, have replaced 4 cam followers on no1 and have renewed the injector on this cyl also, all others have been cleaned. Still have the same knock. Have now stripped off the inlet manifold as I was told it may be one of the flaps broken off and now in the cyl, but all flaps intact! The EGR valve came up as a fault, but is only a year old and the car has done less than 10,000 since replaced, can I test this off the vehicle? The inlet manifold is full of a black tar like substance and there is a lot of it, it is also completely covering the flaps (although they are working correctly) is this normal?
 

Xtractorfan

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S class
I would suggest you put the car back together again and get someone who knows about CDI engines to have a look ..how severe would you say the knock was, did the engine run bad/rough or loose power.. at 110K the engine would have been barely run in..
 
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W205 C250 CDI
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Xtractorfan, I’m not a novice as I have been a mechanic for about 20 years, but am not that familiar with CDI and CAM BUS. It has been on STAR, which brought up the EGR valve fault. The Merc indi thought it was an injector, I thought injector or cam follower hence the change. The injectors were sent away for cleaning and I had to get one new one, (I think it was no1 that was bad). I would be interested to see if this tar like build up is normal, clearly I expected it to be black as inlet manifolds are, I just have not seen anything like this before and wondered if it was normal. Before the knocking it was smoking badly on acceleration more than a CDI should. It also had an air mass meter, again diagnosed on STAR. I just don’t work on Mercs very much other than my own, so looking for some advice from someone who does
 
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W205 C250 CDI
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Update to above. Symptoms are; knocking from front of engine, top rather than bottom, smoke (grey) from exhaust, lack of power but not flat, more smoke on acceleration, no code from STAR regards injectors or engine, but stuck ERG valve. Inlet manifold coated in oily black deposit, (like tar), stuck to everything.
Result: A 2mm hole in the edge of the piston on No1 cylinder!
 

Xtractorfan

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OOps kinda thing you dont wanna hear, I wonder did the missing bit fall down..then ok but if it went into the cylinder chamber then it could have peppered the valves and the inside of the chamber. I reckon a piston will cure your problem. tho have seen this on a BMW engine and when rebuilt did the same about 2000 miles later..
 


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