I just had the long block changed in my 300SD,And the motor has less than 6000 miles.But now there is a loud knock in the front of the motor and it seems to not be fireing on one cylinder.Could this be a valve train problem or something different?The motor was installed by a certified MB mechanic and the motor is a new long block from mercedes and is under warranty but the car will not make it to the place I had it installed.Plus I do not have a manual for this car with all the technical data.Can the forum help me?????

Does the knock seem 2b coming from the cylinder that is not firing? Try cracking open the line at the injector while it is running. If the noise goes away, most likely faulty injector. It could be other things, but I always start simple. Eliminate the easiest/cheapest items first. You could get lucky.

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1984 300D Turbo Sedan (Hilda) 272,115 miles.....
Anthracite Gray/Palamino Leather, I am 3rd owner

2001 Dodge Stratus (Silver) (wifes) 55814 miles...

1982 280TE Wagon Astral Silver Metallic/
Anthracite Velour
260,512 miles (Eva)

1969 230 Sedan Olive Green/Black MBTex
4 Speed Manual
84,213 miles ????
Haus Frau


2004 Boreem Ninja Pocket Bike
Highly Modified 49cc (Ling Ling)

Einigkeit und Recht und Freiheit

Call 1-800-FOR-MERC and ask them about having it towed in. The warranty should cover the towing and all labor costs involved in fixing the problem.

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

Here is a recent thread that is close to your question.

How do I distinguish between bearing knock and nailing?