Research - Why so many OM61X balancer failures?
 

G'day All,

Some thing's been puzzling me for some time - why do so many of these OM617 balancers fail? By failure I mean balancers "spinning" on the crankshaft - which then leads on to people wanting to drill new holes or weld the balancer onto the crankshaft...

How come so many people have suffered from problems with the front balancer on these engines and those little dowel pins?

How can all those 27mm bolts just fall out? It is a high torque bolt - it shouldn't happen.

For those that don't know - the balancer on an OM615 / 616 / 617 engine is held in place by two dowel pins in cut outs on the crankshaft and the balancer.


http://www.peachparts.com/shopforum/...6&d=1299751189



This design is used on other Mercedes engines but I haven't heard of it happening on other engines...


...it seems to be a Diesel thing – and we all know they can shake with the best of them!


A list of engines that uses this system is given in this thread => http://www.peachparts.com/shopforum/mercedes-parts-reference-library/192083-000007008244-dowel-harmonic-balancer-large-engine-application-list.html



So I've come up with this research list which I've turned into a poll to see if we can figure out what is going on.


It seems to me to be possible that the engines fitted with the longer pulley used to power the air conditioning are more susceptible to this problem. But I don't know if this is true. So I need your help to see if this hunch of mine could be right or not.


If you are willing to give more information that would be useful to hear about too.


For example:-


Do you know if “the previous owner” or “the previous owner's mechanic” was in the habit of

1. Turning the engine backwards
2. Not torquing up the 27mm bolt correctly because it is difficult to stop the crank from turning without a flywheel clamp
3. Running the engine with damaged pulleys
4. Fitting the thrust washers the wrong way round
5. Tightening V belts so much you could tune them to twang like high octave violin strings
6. Not paying any attention to the car – only very reluctantly putting in fuel

My 83 300D turbo with 300K miles has no issues with the harmonic balancer being loose. I think it's never been touched maybe that's why? What is the torque spec for that bolt? Is it a one time use bolt? My guess is they only come loose after it's been messed with.

The specification in chapter 03-340 is 270 - 330 Nm

The fly wheel lock special tool is 110 589 00 40 00

http://www.startekinfo.de/etools/dat...n/image003.jpg

http://www.startekinfo.de/etools/content/tool.jsp?toolno=110%20589%2000%2040%2000

It isn't a one time use bolt as far as I can make out.

That is my thinking also. No problem until someone takes it off, and then they fail for a number of reasons, but most probably from improper installation. I hope I never have to do the job - I would probably have to find a really good mechanic and that is hard to do. Maybe the stealer is the best place for this job.

Well if the total issue is the bolt backing off after so many heating and cooling cycles.I now suspect the problem is really the bolt backing off by itself in some fashion.

If any slop at all occurs to let the dowel pins work the impact loading from each cylinder firing will finish the job.

These cars where old prior to most of them being aquired by members. It is easily concievable many had the balancers pulled to put new front engine seals in as well.

It should be possible to fit an impact socket on the bolt and run a small bead of weld out front between the socket and the balancer. Or some tabs welded to the socket properly and welded to the face of the balancer I personally would preffer. . This should provide positive bolt locking.

In the odd case where a new front seal was eventually needed. Just using a hole saw or whatever to clear the weld would let you get into the bolt after you pulled the locking socket or used it for loosening the bolt as well. Install the socket again and close the welds in the cut area the holesaw left when finished.

. . This is preventative in nature and would have to be done well before a failure. You would have to pull the rad to do this properly. It should be quite possible in my opinion.

The bolt feels no heat for practical purposes from the socket being welded on the balancer and there is no way using a reasonable mind that the actual balance of the balancer will be impacted either.

There is a slight possibility it is a combination fault. On the other hand no proof it is either. You could also drill and tap holes in the balancer for machine screw threads through tabs welded to the socket. As long as they are at 180 degrees the balance is exactly the same.

I am not aware of anyone doing this yet but really also see no potential harm. For sure in my opinion the bolt just cannot back out then.

I really preffer the face weld that can be ground off if required as it actually improves the integrety of the crankshaft to balancer bonding. You have improved the factory setup then in my opinion.

I would insist on a really tight socket to bolt head fit. I have dealt with impact loading as the cause by advancing volkswagon injection pumps on the indirect injection models and having to deal with loose balancers as a result.

Wasn't there a TSB on the first turbos in the W116 regarding the balancer? I'm pretty sure I've read that there was but I've never seen the actual bulletin.

It is a relatively common problem. We have never had a real discussion of exactly why it happens to my knowledge but plenty on the aftermath of it.

It may be time to implement a preventor method. My own theory is it really revolves around the original fit of those dowel pins. Or they somehow get distorted or the holes elongated somehow from the impulse loads.

This though is impossible to prove. If it is just the bolt backing off over time we can really prevent it. Or at least totally eliminate that as a possibility over time.

This failure for all practical purposes is the end of many engines .It seems it was never adressed by the factory over all the years of production.

Hunter has pointed out
 

That the OM602 series Engine's Crankshaft Bolt's Brinnel (Hardness Rating) was
REDUCED from 10.9 to 8.8.[the OM602 is the "Improved" OM617 (???) ]
Explanation was that the Bolt Heads were Breaking Off due a combination of the High Torque exerted on the Bolt head;
and the "Crystalline Like Nature" of the 10.9 metal.

[ Kestas (?) ]

(Sounds like Mercedes explanation of the "Rod Bender" OM603 being attributable to the LOW Cetane ratings available in N.A.)

Let's back up a step and look at the Drive Sprocket for the Double Roller Chain
on both engines...
Any problems with them?
'Follow my Drift?
IS the H.B. (With it's drive Pulley)Just Kinda "Tacked Onto" the End of the Crank like some afterthought?
(Granted,Historically;It Do Seem that if it's not messed with,It won't mess with you...)

Age of the "Fastener" BOLT
Walter Mitty type "Pins" for Drive Security???
Etc.,Etc.

What if the Crankshaft HAD Four Keyways inset into it to secure and Drive
the H.B./Pulley system?[Like the single Keyway in for the Sprocket]
('Assumption would be that this would not significantly weaken the crank nose,OR if it did the nose would be strengthened.)

Then there's the Kinda unspoken regimen of using a Puller/Installer to seat the current H.B./Pulley onto the Crankshaft to AVOID stress to the Crank Bolt. (Was the bolt designed to "Pull In" the Balancer ???)

Then there's the "Kabuki Dance Marathon" in Tightening the Crank Bolt to
Specs without Displacing the "Pins" OR "Buggering" the "Pin" recesses in the
Balancer.
[Every time you tighten the Bolt, the Balancer tries to "Torque" the "Pins"
sideways]

I'd not be willing to entrust this Current Scheme to a Mercedes Tech of Less
than 30-40 years experience.

Here's a quote from another list confirming the recall on the balancer:

Date: Mon, 16 Sep 2002 14:42:09 -0400
From: David Bruckmann <dbruckmann@canadianliving.com>
Subject: Re: [DIESEL] Main pulley blows up

There was a recall for this on the W116. You may be able to get the
dealer to handle it for you.

At 9:55 AM -0400 Steve MacSween wrote:
>
>The harmonic balancer on my 116 300sd came apart, breaking the keyways and
>resulting in the front pulley more or less coming off.
>
>The engine still runs fine, so the crank is okay inside. Whether a
>replacement assembly can be bolted on will be seen tomorrow, when we take
>the parts off my wrecked 126 and try fitting them. Most of the betting right
>now is that the bolt will not back in properly. Another shop I spoke to also
>expressed concern that this stuff may also have damaged the sprocket.
>
>Anyone else had something similar happen, or have any advice?
>
>Also, anyone got a parts engine that I can get a pulley and balancer from?
>
>TKS
>
>Steve

Off the Charts II
 

'Worst Case" the Heat Necessary to Force "Red Loctite"
(Their current "MOST Adhesive") to release, damages the Front Crank Seal.

Would it be a Partial solution/You be willing to use it on your Bolt?

H.B. QC is the Problem ?
 

Kerry,

Is the Suggestion that the H.B. Self Destructing "THE" problem or one of many?

Not sure. I'm thinking if someone could find the details of that recall, it might have some information relevant to repairs today, either on those models or other 617's.

The Harmonic Balancers
 

were a problem on some of the CONUS produced SUV Chassis (Tuscaloosa)

EDIT/Clarification:
The Engines Were Imported from Deutschland.

Did "They" ever find a "Fix" ,Might it be the same causation?

Side Inquiry: Does Diamler Benz "Trust'" the Tuscaloosa Plant with Engine Assembly???
OR
Are all the Motors Still Treated to an Ocean Voyage from Hamburg?

I have found only two reasons for the balancers to come off on the turbo 617.


Well two to three LOL number one is being in a wreck where the bolt snaps and need to be redone like with my mentors old 85 wagon. The second it a failing water pump that make the top water pump pully touch the balancer. The 3rd is improper install on rebuilt motors. A very nice3 friend of mine on her got a high mile wagon for cheap because the balancer came off.....after i looked at his car and ran some numbers i found out he had a rebuilt w116 turb 617.950 motor with a wagon head on it and thus why the balancer cam off so easy....it wasnt put on correctly to start with. Army, 10fords and myself all got pins from the dealer that were actually too long. They can be cut, but they should have to.


Id love to rip Mercedes a new one for all the hassle, but it is just a 5 dollar part so not much one can do.

I have heard from more than one retired benz tech that the 240Ds in the w123s had more of an actual problem with them "just falling off".


The correct way to replace the bolt is with a new bolt, pins and spring washers.

Used will do for the pins and sometimes the washer but why chance it?

No failures on any of ours, and they've done many tens of thousands of miles. We've put probably about 225k or so on our 4 617's.....never a balancer issue.