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Old 04-10-2015, 03:04 PM
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Join Date: Apr 2015
Posts: 7
240d "can of bolts" sound - SOLVED: alt housing bolt loose

Hi all - long time lurker (usually in the Porsche section, got a 928 also) but I just purchased a '83 240d a month ago and have run into a new issue that I don't quite know what it might be yet.

In general the car is an automatic that has been in ok running condition. Flattened motor mounts make the car shake fairly violently when parked, but the idle is steady if not exactly smooth. Shifting is also rough but workable, hard but not feeling like it's going to break anything. Other issues have seemed to be either cosmetic or obvious and fixable (wheel bearing on one wheel, minor oil leaks, etc.)

However, after taking a quick jaunt for lunch and fuel today, we got an ugly noise. The drive was ~40 miles total with the stop in the middle for fuel and food. As we got within about three blocks of the house we heard a metallic clang/rattle. At the time it sounded to me like something dragging, exhaust hanger or such. BUT, when we stopped, we still heard the noise. Not unlike a tin can full of bolts. It is *irregular* not lined up exactly with the tempo of the idle, but it does increase if you rev the engine in park. Nothing jumped out at me when I took a quick look under the hood when we got home.

So - I'm hoping it's not something horrible (piston skirts rattling in the oil pan) and maybe something easier like a chain tensioner? No idea where to start looking. I was planning on doing the motor mounts this weekend, but don't want to spend the time if I've got a live grenade on my hands.

These symptoms sound familiar to anyone?

thanks in advance,

Last edited by uncre8tv; 04-10-2015 at 05:11 PM.
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Old 04-10-2015, 03:14 PM
dude99's Avatar
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Join Date: Nov 2009
Location: Vancouver, BC
Posts: 1,492
Check the air cleaner mounts. They are rubber and known to sheer off and let the air cleaner rattle around. The air cleaner mounting bracket is also a known failure item.
1998 Ford F150 -My current Daily
1989 J-spec 420SEL Wife's Daily
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above, an amazingly comfortable car to drive, great drivetrain, but the rust, oh my god the rust
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold
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Old 04-10-2015, 03:26 PM
dkr dkr is offline
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Join Date: Oct 2009
Posts: 649
Diesels generate a lot of vibration. One possibility is you could have something that should be bolted down that is not. I would try pushing everything under the hood back and forth -- alternator, A/C, power steering reservoir, oil filter housing, etc. and see if anything has substantially more play than it should have.

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Old 04-10-2015, 03:33 PM
Diesel Preferred
Join Date: Oct 2007
Location: Charleston SC
Posts: 2,778
I really have good success with a length of rubber tube, hold one end to my good ear and move the other around to find the source of the noise.
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC
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Old 04-10-2015, 03:36 PM
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Thanks guys. Will take another gander when I can finish up work for the day (the joy/curse of working from home.)
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Old 04-10-2015, 04:22 PM
t walgamuth's Avatar
Join Date: Apr 2005
Location: Lafayette Indiana
Posts: 37,990
Better fix your motor mounts...they are simple to do and don't cost too much. All sorts of bad things happen when they collapse.
[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.
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Old 04-10-2015, 05:01 PM
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Join Date: Apr 2015
Posts: 7
Yep, we bought it and that was the first thing we ordered. Trans mount just got here this week. On the shelf ready to go on:
Front wheel bearings
front rotors
front pads
motor mounts
trans mount

HOWEVER - SOLVED the issue today. A housing bolt on the alternator had worked itself loose (mounts!) and was bouncing against the alternator fan. chirp chirp chirp smack smack smack.

So, yeah, lots of things can go bad with bad mounts!

Sprayed a bunch of engine degreaser, didn't let it sit too long, and then hosed the whole thing off. This allowed me to see the alternator fan as a distinct part instead of just a piece of the great greaseball mess. Now to button that bolt up and powerwash the whole engine bay. Any tips there? (cover the battery and fuse box... anything else?)

Thanks everyone!

edit: Just noticed your signature, t walgamuth - you've got good taste! My garage:
'03 Dodge Cummins 2500 (6spd, 4dr, long bed, laramie) (daily)
'83 240d (auto) (runs, mostly)
'89 928 S4 (5spd) (runs, usually)
'77 Scout II Terra (196 4cyl, 4spd) (not running at the moment)
'00 TJ (4cyl 5spd) (sunny days and snow storms only)
'15 Golf TDi (6spd) (her daily)
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Old 04-10-2015, 09:50 PM
TnBob's Avatar
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Join Date: Dec 2009
Location: Shelbyville, Tn
Posts: 1,907
A running motor is much warmer than it off.
Warm grease comes off much easier.
Purple Power sure works nicely too.
1985 300D 198K sold
1982 300D 202K
1989 300E 125K
1992 940T

"If you dont have time to do it safely, you dont have time to do it"

"The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."
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Old 04-10-2015, 11:46 PM
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Join Date: Apr 2003
Location: Phoenix Arizona. Ex Durban R.S.A.
Posts: 5,849
If you can remove the air cleaner housing and seal the air intake hole int he manifold beneath it when you do the power wash. I'm int he process of cleaning my engine bay and you can get to a lot of stuff much better with the air cleaner out of the way.

And yes, purple power is fantastic. I'm in the process of doing incredible things with it to my 240D's engine bay and interior. I'll post a thread on it in the near future when I'm finished.

- Peter.
2021 Chevrolet Spark
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S
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Old 04-11-2015, 08:57 AM
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Join Date: Mar 2006
Location: Mount Holly, NC
Posts: 26,471
Vacuum pump failure could make rattling noises...
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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Old 04-11-2015, 11:25 AM
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Join Date: May 2007
Location: Out in the Boonies of Hot, Dry, Dusty, Windy Nevada
Posts: 9,634
Originally Posted by vstech View Post
Vacuum pump failure could make rattling noises...

Just starting a 240D could make a rattling noise. LOL

there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works
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Old 04-11-2015, 09:13 PM
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Join Date: Jan 2001
Location: Alexandria, Virginia
Posts: 5,477
Nine years ago, my first alarming rattle on my first 240D was a loose alternator. So bad it had chewed the bottom alternator bolt in two!
But that was much better than the alternative ideas that went through my mind.

Happy Motoring, Mark
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Old 04-12-2015, 07:25 AM
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Join Date: Aug 2011
Location: Carolina
Posts: 1,471
Make sure that bolt has the proper nut AND washer on the back side or you'll be tightening it up again and again and again.
Current fleet
2006 E320 CDI
1992 300D "IceBerg"
1984 300D "Blues Mobile"

1978 300CD "El Toro" Gone on to be born again
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Old 04-12-2015, 11:01 AM
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Join Date: Jan 2012
Posts: 450
Originally Posted by charmalu View Post
Just starting a 240D could make a rattling noise. LOL

Thanks Charlie, that made my day...


83 240D - 4 speed manual - Manilla Beige
189K miles, Tachometer mod, cool wooden shift knob from PeachParts, CocoMats, Original factory paint, manual windows, manual sunroof. Starting to add AudioWrap to this car too!
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