Hello Everybody,

Im new to the site, and just picked up a 1984 300 SD, my first Mercedes Diesel. Its pretty clean, runs, drives, stops etc...It does have 251K on it so I know I will be chasing some gremlins. I paid very little for it, so I don't mind putting money into it.

So I have some issues, but the major one at the moment pertains to the gray smoke and clanking noise when running, bought it this way, but the PO said it just started to do it, who knows. The last time the car was used was in 2009, so it has been sitting for a while. Allegedly the timing chain was just replaced, not sure if that means years ago before it was stopped being used,`or just recently.

Start the car, runs, gray smoke from tail pipe. Leave it run for a little, and a clanking noise starts to develop that is idle dependent. Step on the gas, smokes more, clanking noise speeds up. The car drives, but power is down, under load still smokes.

I pulled the intake boot to the turbo, and it spins quite freely, no movement front to back, and almost no movement side to side. Air filter is clean. The oil is dirty, and will be changed soon, but doesn't smell like diesel, just old dirty oil. The clear pre fuel filter is pretty clean, and fuel looks ok. I have about a 1/2 tank in it, and will be filling up with new fuel when I get a chance.

Reading up on the interweb, I heard about this lubro-moly diesel purge, figure I give it a shot. Ran the inlet and return lines into a bottle with the diesel purge, and ran it at different speeds. Didn't really do much.

What should my next steps be. I just bought a boost gauge that I plan to T into the line going from the back of the intake manifold to the ALDA, and a fuel pressure gauge to mount either before the pre filter, or after the main filter.

Any help would be appreciated. Im new to this diesel world, so any acronyms I may miss in the beginning. Thanks again.

Any chance there's water in the tank? Maybe try a fuel additive that dissolves moisture.

When it's clanking at idle, loosen each injector line to see if you can isolate it to a cylinder.

These engines turn the oil black within a few miles. Definitely change 7 year old oil ASAP but don't go by the color to check condition.

Sixto
83 300SD

I put some stanadyne fuel additive in to help with the old fuel. Going to crack some injector lines now.

It is real typical for the Air Filter Housing rubber insulated bolts to have issues as well as the air filter bracket to crack. When that happens they can make all kinds of noise. Easy to do a visual check once the air filter housing is removed.

From the description it is difficult to tell if you are speaking of a mechanical cause or what is called Nailing from the Injectors.

"Start the car, runs, gray smoke from tail pipe. Leave it run for a little, and a clanking noise starts to develop that is idle dependent." This makes is sound like when you first get the engine running the clacking is not their be then starts a bit later.
That makes me think it is nailing (caused by the fuel buring inproperly). When you pre-glow (use the glow plugs) the inital fuel burns well due to the heat from the glow plugs. Then as the engine runs a bit if there is an issue that causes it the nailing can start.

However, you want to listen to the Vacuum Pump with a long Screwdriver applied to the Pump and the other end on your ear to see if the noise is coming from the vacuum pump. Other choices are a piece of broom stick (the one I like) or a mechanics stethoscope.

Other stuff.
If the timing chain really was changed that could possibly change the timing of the Fuel Injection Pump. So that could be re-timed. That is one of the items that can cause the smoke you are speaking of and also the nailing

The valves on these engines need to be adjusted. Lots of prior owners never have that done.

As mentioned if there is old fuel in the tank that can cause smoke.

The nailing can also be caused by the Injector Nozzles being worn out and having low pop pressures.

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84 300D, 82 Volvo 244Gl Diesel

Diesel911, I have a mechanics stethoscope, where is the vacuum pump located? I cracked each injector line, and each one caused a stumble along the way. The air filter bracket and rubber mounts are ok, one is missing closest to the passenger side, and isn't making any sounds.

I think its definitely mechanical.

If one of your rubber mounts is missing on the air cleaner bracket, you are probably getting some metallic chatter from it.

Its not from the air cleaner bracket, I held it tight and no noise is emanating from it. I was able to locate the vacuum pump, I did give it a listen too, and I could hear something moving in there, but don't really believe thats where the clanking is coming from...

It kinda sounds like this, but not as bad..https://www.youtube.com/watch?v=xRAVJTJzxJs

I located the vacuum pump, took a listen, and I can hear movement in there, but don't believe it the source of the sound.

Held tight to the air cleaner assembly, no sound coming from there.

go 6 minutes into this video, and it almost sounds like this, but not as bad.

https://youtu.be/xRAVJTJzxJs

keep probing around with the mechanics Stethoscope and see if you can locate the source of the sound. Of course watch out for hot or moving parts.

Also listen to the Alternator, Power Steering Pump and the Starter while the engine is running.

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84 300D, 82 Volvo 244Gl Diesel

I probed around quite a bit, and it really seems like it is coming from the top end of the motor the the center cylinders. Are the cylinders numbered from front to back, if so, near cyclinder 3

Hello Everybody,

Here are two short videos i took of the noise, the first one at start up, and the second a couple of minutes after running.

https://youtu.be/zPCX2OedVrY


https://youtu.be/Fl9xXYxfIbk

Maybe it's my speakers but I hear a healthy 617 and a squeaky belt or pulley.

Sixto
83 300SD

Well there is something as the last owner mentioned it started not that long ago. In other words it was not there before. Plus you believe you hear something.

I thought that during the first video I did hear something. I am at a loss to identify it though. The engine sounds good in general otherwise.

I think if there were a mechanic in your area that has over the years worked on many of these. I might just get him to listen to it. There is usually nothing better than a person with a lot of experience on an item.

Do you get a clang when shutting down the engine?

In the first video it sounds to me like a slight bit of cold start nailing, which is something they apparently all have as they age. I've only heard one quiet one in real life (sounds like a sewing machine) and it's apparently toast. So I guess I'll take my clattering heap.

I do hear a squeaking, but other than that I don't hear anything catastrophic like in the other video you posted of someone else's car.

-Rog