1985 300D Chirping and Rattling
 

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!

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!!!

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.

my SD would chirp 2nd,and 3rd gear

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.

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

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?

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.