Ok, I was recently driving my 85 300TDT down the road and I noticed that there was an extreme vibration coming from the car. At first I thought that one of my tires had bencome unbalanced since there were new tires put on recently. I slowed down, pulled over and the noise continued, but only in a certain RPM range (2000-3000 RPM with the noise mostly at 2300). When I pulled over, the engine idled terribly. I revved it up, and the noise returned (sounded like extreme diesel chatter). When the engine sat and idled for a while, the idle finally smoothed. Now, I am worried because the previous owner had told me that the oil had been drained once and the filter replaced, but the engine was started without oil. It only ran for about 30 seconds, but it had been revved up during that time. It was shut off and oil was IMMEDIATELY put in the engine and was started immediately after that to get oil circulating. The compression checks out great (or did at that time), and the engine is still powerful enough to climb hills @ 70mph with the a/c on. Does anyone have any ideas in what may be the cause? If anyone is thinking that it's the crank bearings in the motor, you might as well just tell me to go vomit out of disgust and save me the hardship of having to read it...LOL

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1983 300TD 315k miles - Work "truck"
1983 300SD 431k miles
1998 VW Jetta TDi 194k miles
Heartless Libertarian

If it comes and goes my first guess is a fuel problem. I'd say you're due for new fileters and maybe a strainer.

Sixto
95 S420
87 300SDL

The filters are fairly new on the car, but I didn't change the strainer. Do you think that this will cause the car to have that very mechanical sounding knock? Thanks!

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1983 300TD 315k miles - Work "truck"
1983 300SD 431k miles
1998 VW Jetta TDi 194k miles
Heartless Libertarian

I was going on 'extreme Diesel clatter,' not 'very mechanical sounding knock.' It's surprising what kinds of noises fuel system problems can conjur (sp?). When it's making the noise, put your fingers on each injector line and each injector to see if there's a stronger pulse in one injector or through one line. Then loosen the injector fittings one at a time to see if you can isolate the noise to a cylinder.

It's also worth checking valve adjustment and the condition of the adjustment mechanisms before going deeper into the engine.

How's the oil pressure at operating temp idle? Does the noise get worse if you apply throttle with the transmission in D while holding the car with the brakes? Do this for only a couple of seconds and idle a minute before you try again or you'll overheat the AT/ATF. If the noise gets worse then chances are it's rod knock.

Sixto
95 S420
87 300SDL

How long have you run since that oil change, and how long have you run since the fuel filter change?

If your engine was run with zero oil, and oil pressure, for 30 seconds, reved or otherwise, I would doubt that would be enough time to heat rod bearings up enough to cook, not in 30 seconds, and cold to start with!

Injectors can rap pretty loudly, also known as nailing.

story is strange. if it was done and all was well then why would he even mention it? i am suspicious by nature i suppose. bad stories give me the willies.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I thought the story was a bit fishy too, but it ran just fine at the time of purchase and I drove it 300 miles since then (trip back to Colorado and driving around town). The filters were changed 100 miles ago and the fuel is clear. I only fill up at a high volume diesel pump that has a filter on the pump. As for the sound it isn't a normal sound I would associate with injector nailing. Of course, the only injector nailing I have ever heard was on a 6.2 Chevy diesel. Just to find out, how big of a deal is it to replace rod bearings on this Mercedes? I've never really majorly torn into one of these because I never have had a need to. In the mean time, I'll take off the valve cover and inspect the cam and adjust the valves to see if that makes any difference. Anyway, thanks for all of the help thus far. Just in case I'll also replace the filters once again.

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1983 300TD 315k miles - Work "truck"
1983 300SD 431k miles
1998 VW Jetta TDi 194k miles
Heartless Libertarian

Ok, also, my oil pressure is normal, and the noise doesn't even appear when I put it in drive and rev with the brake on. However, I went under the hood and held down the air cleaner to make sure it wasn't that rattle that I was hearing, and I revved it up from under the hood. The engine got around 2100 rpm and I hear this whack (almost like a hammer hitting cement at full force) in what sounded like the #5 cylinder. The engine then sputtered, and returned to about 2100 rpm. The noise scared the crap out of me because it was very loud. Once again, I'll check the cam and adjust the valves to see if that made a difference.

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1983 300TD 315k miles - Work "truck"
1983 300SD 431k miles
1998 VW Jetta TDi 194k miles
Heartless Libertarian

Hmm it almost sounds like nailing. If your oil pressure is fine I would not suspect the rod bearings. They don't heal if you spin a rod bearing you will know it!

Crack the injector lines as it is running and see if you can make that sound go away.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I highly doubt rod bearings.
I put a thread on here somewhere titled "reason to change your motor mounts" or something to that effect.
Check it out.
I drove my car with the oil cooler line spraying out my oil starting at about 4 miles from home...
My rod bearings are fine and I still have good oil pressure.
Remember, when you drain the oil you are only draining the sump, not white-washing the inside of the engine.
Residiual oil can do a lot

I would look into timing/fuel/injectors.
Maybe pull #5's Glowplug and see whats up..