Strange sound pops up every so often. 1983 300SD. I am driving along and all of a sudden I am hearing a crackling noise sounding like it is coming from under the car in the front.. When I slow down (under 30 mph) it stops. Does not happen all the time and does not seem to affect anything. Has anyone had any experience with this? Only happens when I am moving.

Does it do it with the car sitting still, but revving the engine to about the same RPM's?
If not, maybe something's loose that starts flopping around from the wind when moving? A wire, hose, or some kind of cover?

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past MB rides:
'68 220D
'68 220D(another one)
'67 230
'84 SD
Current rides:
'06 Lexus RX330
'93 Ford F-250
'96 Corvette
'99 Polaris 700 RMK sled
2011 Polaris Assault
'86 Yamaha TT350(good 'ol thumper)

Only occurs when I am driving. It sounds like drops of liquid hitting the interior of the engine compartment but nothing is leaking.

any resolution on this? my 80 300d non turbo just started doing this....perplexing!!

You might try sliding the transmission into neutral when you first notice it. At least that might separate the engine and accessories from other things. This noise may be a common defect that I have just never heard of before. Since there are two of you with it at this time I expect someone knows.

Thanks I'll try that.


Any input from anyone else?

seems more prominent upon acceleration...I tried with ac on and off and no noticeable difference


any thoughts?

I believe bearings should get noisier the slower you go, so I'm not sure what you have there.
Belts tight? Fender liners fastened?

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1982 300CD Petrol/Black Leather

Had the same thing once, sounded like a plastic bag was caught in the tranny hump of my car. Ended up being a leaking exhaust manifold gasket. Only sounded under certain load/engine speed conditions.

Its difficult to define a noise with written words... you might peruse my post on diesel pre-ignition to see if there are any tidbits of wisdom there. Is the noise like what you get when you throw 87 octane ( or bad gas) in the blown Miata?

Sure fire way to see is to add some cetane boost to the fuel, or add bio. I have a heavy mix (16 ozs to 20 gals) of cetane boost in the car now, as well as reconnecting the EGR and the issue is mitigated, but not gone. Biofuel ( with a cetane north of 50) is the next step.

If its an pre-ignition engine noise, try cetane boost and see if it helps.

I'm also going to see if I can richen the mixture at part throttle by adjusting that "hat" thingy. When I figure out exactly what that " hat thingy" on top of the IP actually does.

It could be something as simple as an exhuast leak, which even at idle, with a 3' small rubber tube ( winshield washer size) in your ear as a stethoscope, you'll be able to discern.

That "hat thingy" is the ALDA,,, it richens the mixture when you get turbo boost. Lot's 'O folks adjust it to the point the car emits black smoke on hard acceleration, then turn it back a little. It can really improve your acceleration.

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Sir, I have the "hat thingy" but no turbo. Can I assume its there for mid throttle enrichment even in an N/A motor?

I believe you can do the same to the ADA (N/A version).
Yours just compensates for atmospheric pressure.

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1982 300CD Petrol/Black Leather

do NOT listen to this post. ALDA is a fuel control module. it controls how much fuel is provided to the turbo in ACCELERATION ONLY. Meaning if tuned correctly it will lessen fuel injected from dead stops. meaning not so much overfuel and no black smoke. it does you no good anyways to have the black smoke if you want black smoke simply turn the alda up or remove it. it does NOT remove from performance if it is TUNED correctly.

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Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

Yeah anyway, mine doesnt adjust. The threaded screw opened up when I tried. I left the damn thing alone, plugged the resonators back in while I had the upper intake off, and put the EGR back on.

Sorry to tread on this post. My 606 is pinging like heck, and I'm trying to find the cause/solution.