Hey all,

I did some reading on the subject but haven't come to a conclusion yet: I've got a terrible sounding chirp and rattle in my 300. They're both on the passenger side of the engine, sounds like it's between the alternator and the turbo. I poured some water on the alternator belts last night and both noises went away, only to return in a minute after the water was slung off. Easy, tighten up the (new) belts.

No dice. Chirping is slightly better, but not the rattle. Thoughts before I visit my indy on Monday?

https://youtu.be/rAezI2-eHf8

Pull off belt, see if your pulleys are worn out.

The rattle could be bad bearings.

The rattle is obviously something worn out. Pull the belts off completely and start shaking and spinning things until you find what's loose. Most likely the alternator.

Also....it's not a great idea to be dumping water that's splashing around in front of an open turbo inlet while the engine's running!

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Check the bolts 6 IIRC that hold the crankshaft pulley to the balancer, they loosen and break. Also check for broken air cleaner mounts and/or bracket.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

I'm thinking you're probably right.

I replaced the alternator this time last year, but I believe I had to reuse the old pulley from the original so, probably not far off.

Yes, good catch on the water near the turbo statement. D'oh!

Will have the indy check it out! I ended up wasting too much time over the weekend to play much with it so, to Blue Ridge Mercedes we go!

Update: Diagnosis- failed alternator. New Bosch unit coming in this afternoon and being installed later on today.

Also looking for a KNOWN GOOD fan clutch for the 617. Both of the used ones I've purchased had lots of play in the shaft and wobble in the blades. PM me if you've gotone.

Some good rebuild vids here.

Rebuilder in a box

I bought a kit for my Dodge and they sent OE parts - Denso in my case. Vids apply to most/many alternators.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

my SD would chirp 2nd,and 3rd gear

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

I always squirt water on my belts when they start to chirp. I don't think the air inlet is anywhere near any of the belts, is it? It's up front near front of hood on my '85. More chance of getting water in when driving in rain?

I had that chirp last year. Water stopped it temporarily. I applied some belt dressing and the chirping went away. As it happens, the chirp came back again yesterday. Again water made it go away. Now all I have to do is find that belt dressing in my shop

Got a feeling chirping happens in Spring because car is stored for winter and rust develops on pulley surfaces.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

The OP had the intake tube off the turbo and was pouring water on the belts right in front of it in his video.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

OK sorry - I didn't watch the video.

Just looked at my intake - The flat air inlet just under the hood must pick up quite a bit of water when it rains. That would go into air cleaner. What happens to it from there? Does it just evaporate or get sucked through the filter?

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5

To update with the remedy for anyone finding the same problem: I swapped in the new Bosch alternator and all is well. Good timing, too. As I was returning home from picking the alt up at my indy's shop, my exisiting alternator was crapping out at idle and throwing dash lights. FWIW, it was an Autozone/Advance reman unit.

I got the new unit in a did a long diesel purge, the car is almost as quiet and smooth at my old 350SDL now.