Good Morning all,
This is on my 86 300sdl, a little heads up for everyone. My idler tension pulley started squeaking last week. Thought it was the shock absorber going bad. I ordered a new pulley, tensioner arm and shock last Saturday from Pelican. The squeak wasn't that bad, I figured I could continue to drive it. On the way to work yesterday morning, I heard loud shrieking and some clanging sounds when I turned a corner about one mile from the house. I stopped, opened the hood and my serpentine belt was flopping around and hitting the fan at times. The tensioner arm was jumping up and down. I limped back home and parked it. No damage done. A new belt will also be installed when my parts come in ( which should be today).
Moral of the story: Listen to your car. It is telling you of imminent failure.

This could have been a lot worse. Loss of belt, overheat, crack of #14 head

__________________
John
1986 300sdl
1985 380se

Glad to hear it didn't do any damage. Good luck with the repairs. I found iy way easier to access everything with the radiator removed.

__________________
Chad
2006 Nissan Pathfinder LE
1998 Acura 3.0 CL
OBK#44
"Pleasure in the job puts perfection in the work." - Aristotle (384-322 B.C.)

SOLD
1985 300TD - Red Dragon
1986 300SDL - Coda
1991 - 300TE
1995 - E320
1985 300CD - Gladys

Two positives: first, you got on top of it promptly and ordered the parts to do the job (as opposed to the "I'll ignore it until I can't drown it out with the stereo" approach). Second, it gave up close to home.

Not all stories go that way.

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I have the parts to do this repair.....and my "rattle" noise seems to be getting louder. Wish you lived closer brandlj, I could assist in the repair. Then you could assist in the 87 Champagne work.

Do you remember when I did my initial diagnosis of my serpentine belt wobble and tensioner damper? Yikes! Back on February 16th!! Bought some 1987 Champagne

Here's the video that I posted on February 16th --- must click on the pic to start it. I can hear it at work; wonder if it sounds a lot different now.

__________________
daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
Cluster Needles Paint
New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

Hey David, Yes my tensioner arm is now bouncing around more than that. In fact there is a glob of very black goo, directly under the shock absorber, which made me think that the shock let go and spilled its guts. I was just going to replace the shock but decided to order everything associated with the shock. Hey, it is 26 years old. My car made a squeaking at idle, loud enough to hear with the hood closed, sitting in the driver's seat. Luckily I have another car to drive because I don't have a day off til l next Thursday.
It will be a tight fit working on this with the radiator still in the car, but I just replaced said radiator, hoses etc... earlier this spring. Once I get the fan off the water pump pulley, I plan on putting a nice big piece of cardboard over the beautiful, undamaged fins of the radiator and then I should have enough room.

__________________
John
1986 300sdl
1985 380se

Believe me, I learned my lesson with that a long time ago.

__________________
John
1986 300sdl
1985 380se

I agree, but I just replaced the radiator and hoses earlier this spring. See David's post as to my plans.

__________________
John
1986 300sdl
1985 380se

I just went through this on 1987 300TD

Any of the devices on the serpentine belt can squeak. It is very hard for humans to locate the source of high frequency sounds especially when there is a clacking engine nearby.

On my car,
- the alternator bearings were bad (rebuilt by motor shop $50)
- water pump pulley hub not parallel to flange, rim hitting harmonic balancer, PO just replaced water pump (put pulley in press, straightened hub $0)
- tensioner hub and pulley bad (replaced hub, pulley, spring and shock $200)
- air conditioner pulley bad sliding back and forth on clutch ($500 for compressor, misc parts and ac recharge)
- and of course a new belt $25

Car is quiet as a mouse now...but my wallet is dead.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

So true. When I started to hear a squeak last Saturday, I removed the serpentine belt and played with all of the suspects mentioned in your post. All were just fine except for the tensioner arm and shock. I put it back together and used a long tire iron to slowly lift the tensioner arm and the squeak disappeared. I had to be very careful of the moving fan. Hopefully this Thursday will be a very successful and rewarding day when I replace the offending parts. My wallet is not too dead though. The whole thing will end up costing around $120.

__________________
John
1986 300sdl
1985 380se

My parts arrived today from Pelican. I really enjoy the online ordering and the fast free delivery. Parts quality looks excellent. Thanks to the guys at Pelican Parts.

__________________
John
1986 300sdl
1985 380se

I just leaned this. Mine was alternator pulley. Came right off on my 606. I was wondering what that chirping was under hood. Better to check sooner than later.

__________________
What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius