Today I took delivery of a '87 300TD, a one owner wagon with 122K. Bought it on ebay, had it shipped from NJ to Portland, OR. I already have one, an excellent example with 102K, so I guess I'm starting to hoard them .

The car has the typical misrepresentations / omissions that you get from buying on ebay but what concerns me most is a low rpm knocking sound. I brought it by my MB mechanic, he thought I had a noisy injector or pump. Being a Friday afternoon, he recommended running a bottle of injector cleaner through the tank and seeing if it helps.

The noise has a fairly irregular pattern at idle, a metallic rapping, it increases at tip-in and then gets lost among the general engine noise above 3K rpm. The background sound from the valvetrain is nice- sweet and smooth, just like my other wagon. Seems to run and drive just as well as my other, same smooth powerband, throttle response, balanced idle, etc. Not a bad running car at all, just a noisy one. Any thoughts?

Bob

Run a tank of B-100, and be ready to change the fuel filters. The B-100 should help clean out the entire system, and also quieten the pump. Probably would not hurt to get out on the road and really cruise for a while.

These diesels are not meant to sit still....

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87 300SDL - 215K Miles !!
99 F-350CC Dually PSD - 190K
86 300SDL - 189K
All on B-100

Sounds like a lifter.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

You'll need to explain "metallic rapping" in a bit more detail or provide a sound clip.

The engine can suffer from an "injector knock" which will have a soft metallic sound and emanate from the top of the engine.

Or it can suffer from a lifter which will have a hard ticking sound and you'll really hear it at the back of the tires in the fenderwells.

Both sounds disappear with increasing engine speed.

Here's a link to the audio clip....

http://www.cascadiaclassic.com/300TD.WAV

Hey Bob

The 87 that I bought from you in Nov 2005 has been great. I would love to come by and see your two new ones sometime - just to check them out. Who is your mechanic? I have nothing of value to add re the noise unfortunately. Good audio though.

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1987 300TD 231,000
#22, afterglow, plastic fan, euro lights, alternator upgrade, cluster housing update

That is the way my 86300sdl sounds until it warms up. The clacking disappears after driving about 10 miles.

After my drive to work or home after work, that noise will be completely gone.

John

Sounds like a bad injector and/or prechamber.

Its not a lifter, a lifter has more of a metallic edge to it.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I sent you a PM aersloat, good to hear from you. The audio btw was from my Nikon D2x's built in mic!

I agree. Additionally, the noise is not steady. A lifter is a steady metallic tapping that doesn't vary until the oil pressure comes up with increased rpm's.

Sounds like my car. At least I think it does.

Call it a super hijack, but here is a video and sound file of a clacking noise. This sounds the same to me as the file cascadia put up. Is it injectors/prechambers? Maybe we could start a reference library of bad sounds for people to play match that sound?

video is here:

http://www.pauldrayton.com/uploadfiles/merc/nailing/nailing2.html

If this is prechambers, how do I find which prechamber it is that is the problem? The noise doesn't go away when I undo the injector lines individually.

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1983 240D Silver/Blue "Sadie", unknown miles. 100k miles on WVO single tank, converted to 2 tank about 10k miles ago, FPHE, Injector Heaters, Aux Fuel pump. Alcohol/Water injection. Frantz oil bypass filter
1992 300D 2.5 Turbo Green/Tan "Jade" 267K miles Stock.
1992 300D 2.5 tan/tan "Rocky" on 2 tank WVO. Pressure actuated Turbo "rat's nest" surgery completed. 197k miles

Since your mechanic guessed injection pump I might take the load off the vacuum pump by creating a very large vacuum leak and see if there is any difference.
That noise certainly sounds irregular. The vacuum pump is on the nose basically of the injection pump and that may have lead the mechanic to the pump. A fairly easy test to do. Probably meaningless yet still. Usually hard to determine from a sound blurb.
As for the gentleman that loosened all his injector lines off and still had a simular noise. You eliminated the prechambers and injectors totally in my opinion as the possible contributor to your noise.

The vacuum pump looks fairly new, still, I took your advice and created a big leak, no difference. Here's an update though....I had a bottle of Lubro-Moly diesel purge run through the pump and the noise went away in about 30 seconds. Unfortunately it returned soon after the treatment. The next day I ran 2 bottles of diesel purge through the pump, varying the rpms, a good 30 minutes of cleaning. As before, the noise went right away, and then returned after about a minute of driving.

Another weird side effect is that in the morning, the first start of the day, it doesn't make the noise, however it smokes quite a bit, blue smoke, lots of it. As the car warms up the noise returns and the smoke disappears. Any opinions?

Yep just like I said before its a bad injector/prechamber. Yank them and have them tested.

Don't ignore it to long.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Hello Cascadia,

Welcome to the forum. You are a brave man to buy a car without seeing it in person. When I heard the ticking sound your engine is making I was waiting for the Salsa Band to start playing. Good luck diagnosing your problem. May it be simple and cheap to fix.

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Doug

1987 300TD x 3
2005 E320CDI