Hi Guys,

My '87 300D turbo has a new LOUD growly rattle at idle. It quiets down at higher rpm, but at idle, it really gets your attention. Checked power steering fluid level. A friend said it might be the vacuum pump. Before I tear into it, I'd appreciate any other thoughts you might have. Thanks!

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1987 300D with 201k miles.
1985 F350 Ford dually 6.9 diesel
1988 F250 Ford utiilty truck 7.3 diesel

i think those engines have a reputation for losing their vacuum pumps catastrophically.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Might check your exhaust system, make sure it's not hitting anything.

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I had a real nasty rattle that developed a while ago...it would be real loud at idle but would disappear at higher speeds. I couldnt figure it out, and with loud engine noise, I couldnt pinpoint the exact source.

Then one day when I was removing the air cleaner housing, I found the blue plastic cap to the low pressure port for the AC system that I had lost a while ago. After removing the cap, I never heard the rattle again!!

THis is probably more common than you think because most of us set down bolts, sockets etc. in the little "tray" at the air intake and end up "losing" something.

Mark

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

Don't forget heat shields, fan shroud, loose drive belts and motor mounts.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Check your Air Cleaner.....it is attached to a bracket with 3 rubber mounting "screws", Phil has a photo of them in parts......those are known to break over time........whole air cleaner dances around, makes a decent racket.....

SB

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Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

.......he's got the 603..........the air cleaner is not an issue.

If air con is on while you have the rattle, might check the clutch on the compressor. It can make a hell of a noise.

Regards

Run-em

I'm actually in the middle of installing a new ring gear on the 240. It developed a crazy rattle...which I've narrowed down to the bell housing. Since the rattle started exactly when the started started 'missing' - I'm fairly certain that the a couple of broken teeth are being thrown around in there. It sounds terrible.

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1973 280 - Current Project Car
1979 240d - 100% Stock
1982 380sl - 100% Stock
1985 190e 2.3 - Heavily Modified

I have a brand new a/c compressor on it, so I doubt it's that. I guess I could remove the fan belt and start the car. The vacuum pump doesn't run off the fan belt. If the noise stops, is that conclusive it's the vacuum pump? Or is this a bad idea for reasons I haven't thought of?

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1987 300D with 201k miles.
1985 F350 Ford dually 6.9 diesel
1988 F250 Ford utiilty truck 7.3 diesel

IIRC, on your car, removing the belt also stops the water pump from turning. Don't overheat it...should be ok for a minute or so.

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1973 280 - Current Project Car
1979 240d - 100% Stock
1982 380sl - 100% Stock
1985 190e 2.3 - Heavily Modified

Check the belt shock. Press it to the side (carefully) when the engine is idling. If it quiets down, you've found the problem.

Good idea,

I will try the shock before doing anything else. Thanks!

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1987 300D with 201k miles.
1985 F350 Ford dually 6.9 diesel
1988 F250 Ford utiilty truck 7.3 diesel

Do the simple air cleaner check first as this is very easy & cheap to fix.
Mine made the housing hit the wheel well at idle and sounded like a Godzilla diesel knock or very bent dirve shaft. PO thought it was exhaust. I think I paid $4 each. Verify which style you have.

Thanks for all the input and the nice email from Billybob about this. I've looked at it and here's what I found:

1. Bottom of tensioner shock absorber contributes to the noise. When pushed with a stick sideways while engine is running, it quiets down some.
2. Serpentine belt (very new) has about 1 inch of slack when pushed downward (engine off). With engine on, it bounces quite a bit at idle.
3. I did the hammer-handle listening trick with the end of the handle resting on the vacuum pump. While I did hear something, it didn't appear to be either loud or obnoxious.
4. With the engine at idle, the lower shock absorber bolt is vibrating. I assume this is normal.

I assume all this points to installing a new tensioner shock absorber. Any ideas about the serpentine belt slack? Is my spring worn out, too?

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1987 300D with 201k miles.
1985 F350 Ford dually 6.9 diesel
1988 F250 Ford utiilty truck 7.3 diesel