99 OM606 Knock - PeachParts Mercedes-Benz Forum

treetops · #1 12-01-2015, 07:01 PM

Hi guys n gal(s), Hope you all had a great TGD or 11/27/15 in your relative parts o the world. My DD has developed a serious, to me, knock all of a sudden. I am hoping it is an external part rather than internal. Regular maintenance been done; oil fluids...etc.

Last night I had to give is good stomp to get on the highway and when I got off I noticed a tick tick ticking louder and different then normal. Got some gas checked the oil, added a 1/2 qt thinking it couldnt hurt. Noise went away briefly at idle for about 2-3 minutes. Drove another 15 minutes, some uphill and then it got way worse, louder. LSS I pulled over and got a tow home.

I just had a chance to check the engine over and see that there is new wear, cut metal, on the alternator where the pulley meets the housing. Also noticed that the tensioner was rocking a lot more than last time I looked...so Im thinking its either or both. Been meaning to replace the tensioner for about a month or two.

Started the car, knock still very much there(see youtube link), turned it off checked the alt again. It turns easily then gets really tight, then easy again. Too boot, looks like the battery died(11.2V after glow cycle) and now it start and wont turn over, like a dead battery.

Please take a look at the video and if this seems familiar to you, let me know your thoughts....good and bad.

https://youtu.be/L-7J6ur3Y7M

Also pic of the alt with the near wear marks.

mannys9130 · #2 12-01-2015, 07:21 PM

Remove the belt and start the engine.

Does it still make the noise?

nelbur · #3 12-01-2015, 07:24 PM

I think I would start it up BRIEFLY with the belt off to see if the knock is still present. This should give an idea as to the source of the knock.

mannys9130 · #4 12-01-2015, 07:27 PM

A cold engine will be fine for a minute or two to see if it's still knocking and where it's coming from. Diesels don't create much heat at idle.

KarTek · #5 12-01-2015, 07:28 PM

I have not heard this before but my instant gut response is that it's the alternator overrun pulley.

Reasons:

1. Sounds like it's coming from alternator area.
2. Poor charging of the battery.
3. Fresh wear marks on alternator.
4. My friends Golf just had the same problem and it sounded similar.

I would loosen the belt/remove it from the alternator and start the engine to see if the noise continues. If you do this, make sure the belt is loose from the crank pulley, otherwise, it can get pulled in, slung around, wrapped up in the accessories, take a finger off, etc...

Another thing you can try is to take your finger and touch the top of the alternator to see if the knocking is local to that area. Again, no body parts or loose clothing should come in contact with the moving belt obviously...

Finally, and you should probably try this first, remove the belt from the alternator and try to wiggle the pulley to check for looseness.

In the end, if you need to replace the pulley, I have the fancy tool set that some of these things require. (it was required on the Golf) I can send you the kit if it helps.

treetops · #6 12-01-2015, 09:13 PM

Hey thanks Gents, Yup its the alt. Took the belt off....everything...and no more knock. Whew, thats a load off my mind as I did start to imagine all kinds of sources of this knock inside the engine.

I tried to spin the alt pulley and it is tight, no easy spinning with a little lateral play. I could rock it a tad.

Now getting the old unit out does not look too easy. I will see if there is a how to here or somewhere and I do recall someone just did this on a 95 to change the pulley to a over run type(?)

If anyone has a FSM procedue on RnR the alt, that would be great.

EDIT: Found a write up so getting out should be straight forward. This for others if they need it: http://www.peachparts.com/shopforum/diesel-discussion/213992-w210-om606-turbo-alternator-removal.html

Now, how can I tell if the alt is bad or its just the pulley? Take it to a shop and have them test it? Thanks in advance

KarTek · #7 12-01-2015, 10:01 PM

Pretty sure it's just the pulley, the engine vibration hammers them pretty badly. They will slip under load which causes charging anomalies. You should be able to get the pulley off without removing the alternator. I'll give it a look tomorrow morning in the light to see if it's possible.

mannys9130 · #8 12-01-2015, 10:49 PM

Awesome.

Whenever someone says they have a noise that sounds like the front of the engine, I say take the belt off and start it up. If it's a belt drive issue, it won't be noisy.

I actually took the belt off my engine and drive down the street and back real quick to see if it was a belt drive noise. It wasn't. The engine did not overheat.

tjts1 · #9 12-02-2015, 01:15 AM

I just installed a 150a W220 alternator + VW OAP into my 97 OM606 to replace the 90a bosch remanufactured alternator the previous owner installed with a solid pulley. I don't know if the 97 had a solid or OAP originally but sweet murciful silence, the engine is so much quieter. The solid pulley caused the belt tensioner to rattle like a can full of bolts even after replacing all the tensioner components. I was really scratching my head until I learned about OAPs. The pulley was $28 (INA brand) and another $8 for the 33 spline tool. I'll installing the same setup in my 87 soon.

If you are removing the alternator you might consider also replacing the voltage regulator and inspecting the slip ring.

Mölyapina · #10 12-02-2015, 01:44 AM

Quote:

Originally Posted by tjts1

I just installed a 150a W220 alternator + VW OAP into my 97 OM606 to replace the 90a bosch remanufactured alternator the previous owner installed with a solid pulley. I don't know if the 97 had a solid or OAP originally but sweet murciful silence, the engine is so much quieter. The solid pulley caused the belt tensioner to rattle like a can full of bolts even after replacing all the tensioner components. I was really scratching my head until I learned about OAPs. The pulley was $28 (INA brand) and another $8 for the 33 spline tool. I'll installing the same setup in my 87 soon.

If you are removing the alternator you might consider also replacing the voltage regulator and inspecting the slip ring.

What's the advantage with a higher-output alternator? Are you running a lot of accessories?

mannys9130 · #11 12-02-2015, 02:14 AM

A higher output alternator charges the battery quicker and more thoroughly. A higher output alternator also prevents power from being drawn out of the battery when you have the electrical system maxed out. If you have high beams on, air conditioning on full blast, aux fan on, stereo turned up loud, etc all of those loads make it hard for the alternator to keep the battery charging or charged.

KarTek · #12 12-02-2015, 07:43 AM

I checked this morning and it looks like there's enough room to get the small version of the tool in place without removing the alternator from the car.

Let me know if I can help out by sending it to you.

treetops · #13 12-02-2015, 08:15 AM

KArTek-sending you a pm

tjts1 · #14 12-02-2015, 09:21 AM

Quote:

Originally Posted by Mölyapina

What's the advantage with a higher-output alternator? Are you running a lot of accessories?

If I drove long trips lets say 15 minutes or more everything was fine. But if I did a short trip lets say the minutes it takes me to get to work, the next time I tried to start it the battery was flat. Replaced the battery, cleaned all the terminals grounds etc, even tried an 80a alternator I had from another MB, no change after a cold start + short trip The battery was dead or barely able to crank the engine.

Turns out the w210/om606 can afterglow the plugs for up to 3 minutes after cold start depending on the temp. The GPs draw 10-12a x 6 = 60-72a. At idle the 90a alternator is outputting 50a. So if you cold start then do some city driving where you're idling a lot, it can take a long time before you recharge the battery enough to handle another cold start in a few hours. With the 90a alternator, the voltage would rise very slowly from 10.5v immediately after start up then 12v after more than a minute and I never really idled it long enough to see it touch 14v.

The 150a alternator outputs 90a at idle. It has 12.5v instantly after cold start with the GPs still on and 14v the moment the GPs shut off. As soon as that happens the car is ready for another cold start.

The 87 300d which doesn't afterglow gets by just fine with its ancient 70a alternator. I just want to replace it with something newer.

EDIT: Forgot to mention that I also installed a 4awg cable between the alternator and the big + terminal on the driver's side inner fender in parallel to the existing wire. The existing 6awg or 8awg (can't remember) was too thin for 150a.

treetops · #15 12-04-2015, 05:18 PM

Welp an update of sorts. I got the tool, Thank You KarTek, took off the pulley with Alt still on the engine. Not too hard. a 7/8ths box wrench on the spline tool and a 12mm socket w/breaker bar on the torx. Mine was very tight so I used the socket side to break it free pulling itCW

Put the new one on, belted up and the knocking is still there.

I did confirm no knock sound with the belt off again.

The old pulley was definitely seized because when I inserted the spline tool into the new one it did indeed free spin CCW, while the old one locked up both ways.

Now to the knock, I came across this vid, quite informative, that to me indicates the net effect of the seized pulley trashed the tensioner or hastened its death.

https://www.youtube.com/watch?v=fyosuYbPxr4

I now have the Alt off to have it checked out, why not, and next up is the tensioner....arggghh.

One thing I noted is that the new pulley sits out a bit as compared to the old one. I'm pretty sure I tightened it down securely. There is a difference which I do not think is right.

All thoughts appreciated, thanks.

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