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Euro Triad '84 280se '83 280e '85 500se
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Discussion Starter #1
Hey guys, my '77 300D has a knocking sound when it's cold and I apply moderate acceleration. It doesn't happen at idle, only when accelerating. It also goes away when it reaches operating temperature.
I adjusted the valves all to spec and I have no clue what it is. It's a pretty loud clacking sound that I can hear from inside the car. I haven't touched the injection timing nor have I really touched the injectors since I bought the car as it was running well. Any ideas? :confused:
 

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'86 W123 200, OM617 non-turbo, bastard 5-speed; '95 W202 C250 Diesel, OM605 non-turbo, 5-spd man
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That sounds exactly like a diesel.

I wouldn't worry too much. I'd have the injection timing checked to give myself peace of mind, then leave it there. Cold diesels are clattery when cold.
 

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Euro Triad '84 280se '83 280e '85 500se
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Discussion Starter #3
Yeah, I will definitely do an injection timing since I have no idea the last time it's been timed. The only thing that worries me is that I thought the knocking went away when it's warm but if I listen from the engine compartment I can still hear it very faintly when I rev up the engine. It's about 95% gone but it's still there.
 

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1984 300D
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Hey guys, my '77 300D has a knocking sound when it's cold and I apply moderate acceleration. It doesn't happen at idle, only when accelerating. It also goes away when it reaches operating temperature.
I adjusted the valves all to spec and I have no clue what it is. It's a pretty loud clacking sound that I can hear from inside the car. I haven't touched the injection timing nor have I really touched the injectors since I bought the car as it was running well. Any ideas? :confused:
Either or both.

If you have the Valve Cover off Check the Camshaft Timing.

If the Fuel Injection Pump has not been re-timed but the Timing Chain and Gears have continued to stretch/wear the Fuel Injection Pump Timing will be a little late.

As compression gets lower it will also cause nailing.

I am one of those people who lets the Car idle a bit to warm it up before I move; unless I am in a big hurry.
 

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1981 Mercedes-Benz 300TD
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I am one of those people who lets the Car idle a bit to warm it up before I move; unless I am in a big hurry.
I read in my TD's owner manual that Mercedes recommends you simply drive to warm it up. I've also read that diesels in particular produce a relatively small amount of heat while idling so they take a while to warm up. My TD will usually take at least 10 minutes to reach 80C idling. When I crank it up, I'll high idle it around 1100RPM, mostly to get the nailing to stop and because theres usually a lazy missing cylinder that a high idle smooths out. I'll do that for about 10 sec, check its 900RPM idle for a sec and start driving very easy ~15sec after start up.

PS: I explained in detail because everyone likes details AND so you all can clearly comment and share info. on what I post. I DO appreciate feedback!
 

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Timeship, see you yesterday, but you already knew that.
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Check the flywheel for cracks and make sure the torque converter bolts are all tight.


You wouldn't believe how many nuts and bolts a diesel will loosen with valves that are out of sync, due to vibration.
 

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Euro Triad '84 280se '83 280e '85 500se
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Discussion Starter #7
Thanks for all your help and input folks, I greatly appreciate it.
I went ahead and timed the injection pump today and it purrs like a kitten. The timing was about 10-12 degrees retarded so I'm glad that noise and your input led me to check it :thumbsup:
 

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1984 300D
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I read in my TD's owner manual that Mercedes recommends you simply drive to warm it up. I've also read that diesels in particular produce a relatively small amount of heat while idling so they take a while to warm up. My TD will usually take at least 10 minutes to reach 80C idling. When I crank it up, I'll high idle it around 1100RPM, mostly to get the nailing to stop and because theres usually a lazy missing cylinder that a high idle smooths out. I'll do that for about 10 sec, check its 900RPM idle for a sec and start driving very easy ~15sec after start up.

PS: I explained in detail because everyone likes details AND so you all can clearly comment and share info. on what I post. I DO appreciate feedback!
I guess I am a Rebel.

I also did not mean I idled the Car until it reached 80C. I am talking about allowing the Car to Idle 1-2 minutes.

If I thought I could remember to disconnect it before I drive off I would use the Block Heater.

I believe warming the Engine reduces upper Cylinder Wear and when you Car starts moving the Fuel burns better.
 
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