They Said it Can't be Fixed - A Journey to the Inside of a Mercedes Bluetec

There is something about our parish festival that kills my car.  Last year, it was a flat tire, this year it's something probably expensive and hard to get to.

2012 GL350 with the OM642 Bluetec diesel.  It started making a light ticking noise when coasting down a steep hill this weekend and on Monday it escalated to a full on brutal tick o' death at all RPMs.  The noise is directly related with engine speed, not road speed.  I put my stethoscope on it and it seems loudest on the right side valve cover and fuel rail as well as the pipe connecting the turbo to the DPF.  The noise is present on the timing covers, but significantly quieter than on the right side.  I've been listening for the infamous timing chain stretch noise -- ticking noise at startup that goes away pretty quickly -- and haven't heard it.  That doesn't necessarily rule out the timing chain, of course, but everything I've read seems to indicate that it comes on gradually.  My guess right now is collapsed lifter since it sounds a lot like my old van would sound when the oil got old, thin, and a little low.  Don't have a way to check oil pressure at this moment, but I wouldn't rule that out.  Oil level is good, oil is about 2000-3000 miles old and is the right oil spec from Pentosin.  It sounds like this:  https://youtu.be/kAOI3RRWVUo

Guesses?

EDIT

21NOV2018 - I've asked to go ahead and move this to the build thread forum.  Originally, I was looking to for help to remotely diagnose the noise, but I've since employed the services of two different shops here in town and while neither has torn the engine down, they both say it's something internal that has "let loose" and the only option would be to get a reman engine from Mercedes.  That's a $20k repair on a vehicle that *might* be worth $18k.  Not gonna happen.  

Instead of being a cry for help to try to figure out what the noise is, this has now officially become the documentation of my journey into the inner workings of the OM642 Bluetec engine.  I've head the head covers off already, and that's covered in the first couple pages of the thread, but it sounds like the next step is to get the heads off and then, very likely, to pull the engine.  Pull up a chair and the soothing beverage of your choice, and join me as I jump down the rabbit hole.

Sounds like an injector making the noise.. 

Did you fuel anyplace different before this started?

Can you disable injectors one by one by unplugging them? 

In reply to No Time :

No, I hadn't fueled up in a little while and it's got about a half a tank in it now if memory serves.  I thought about injectors -- I unplugged the first two on that side (one at a time) and didn't get any change in the noise.  When I go out there again tomorrow, I was going to pull the air intake pipe off so I could get to the other injector plugs and do the same thing to the other 4 to see if the noise goes away.  That would be a valid test, right?  Nothing that weird about diesel injectors?

Unplugging the injectors one at a time should work to diagnose if it’s injector related  

I used to loosen the lines to turn off injectors on mechanical systems, but unplugging should of work for modern systems. 

I unplugged each injector one-by-one and there was no change to the sound.  When I first started it up, though, it sounded like a bag of wrenches for a second before settling in to tickticktickticltick.  I'm thinking timing chain stretch.  Of course I can't see the tensioner since they apparently installed a baffle under the oil fill which covers the tensioner and chain.  I guess I'll have to order a chain and hope.

How does the tensioner work on these? Spring loaded? Hydraulic? Probably doesn't matter since you need to go in anyway, but it would be interesting. Does the motor have any other "while you're in there" things? I obviously haven't taken apart an MB six, but the V8 I took apart had about 30 different very specific O rings under the timing cover and MB specified a very particular sealant. 

In reply to mazdeuce - Seth :

It's hydraulic and I'll replace it when I do the chain.  I don't think there's really anything else major -- I need to put in a new intake-tube-to-turbo seal, and the injectors should get new o-rings and washers.  There is a specific Loctite sealant specified to use as the gasket for the valve cover, but I don't need to take the timing covers off -- the chain is split, attached to the new one, and pulled through the engine.

In reply to No Time :

Yeah, absolutely do not disconnect the line from a modern injector.  It runs an extremely high and constant pressure (23,500 psi, yes twenty-three thousand psi) to the feed side of all of the injectors, then switches them on/off like a gas engine.  Unscrewing one is a great way to get an injection injury.

In reply to wae :

Good news about the split chain. The original writing of the service CD for the R63 referenced a split chain, but when they built it they said nah and made you take the whole damn thing apart. Not a huge deal for me what with the heads needing to come off, but....... 

I looked at a parts diagram and the system looks about 99% like the Mercedes V8's. They don't recommend replacing the guides with the chain? 

In reply to Matthew Kennedy :

Even mechanical injection systems use pressures high enough to cause injury if you aren't careful.

That why on mechanical systems you only back off the nut on the line just enough to break the seal (fuel will start to leak at the connection), and don’t disconnect them. 

In reply to mazdeuce - Seth :

Most of what I've read indicated that the guides were fine and they just pulled it through without taking off the front of the engine.  

I'm seriously considering just throwing in the towel on this one.  Between the parts and the special tools that I'd need to buy, I'm already at about $700 and I haven't turned a single wrench, so if the indy MB shop up the road can do it for under challenge budget I may just have them do it.  In fact, the more I think about it, I have to wonder if the tensioner failed -- it went from "hmm, I think I hear a little bit of a noise" to "holy crap something is seriously wrong with this thing!" in about 20 miles, maybe fewer.  Even Mercedes couldn't build a chain so poorly that it would stretch that much in 20 miles!

I was in a pretty foul mood about this, but I had this epiphany last night and I'm in a much better place.  A friend of mine texted me with a book suggestion to which I responded that the timing was good and I could use a little bit of calm.  When she asked what was up and I started to reply, it occurred to me how ridiculous I sounded that my worst problem was that my Mercedes was broken down.  In fact, I started laughing at myself so hard I had actual tears.  So after taking a step back (and not having heard back with an estimate from the shop I called who claimed to have some experience with doing this job) I don't think this is so bad after all.  For the first special tool, I need to adapt a slide hammer to be able to thread onto the injectors and some studs in the valve cover.  I have a slide hammer, a great hardware store, and a welder, so what am I whining about?  Tonight, I'll move the car into the workshop and tomorrow I'll build the tool and tear off the valve cover to verify that it is slack in the chain making the noise.  If it is, great - on to the chain replacement and more special tool building.  If not, then more diagnosing!

Heck, maybe I'll go ahead and fix the O2 sensor and the M55 motor (again) while I'm at it since the car will be down for a bit anyway.

(And yes, I do recognize that this is a pattern.  I guess I need my own logo: bitch twice, wrench once?)

I got a hot tip last night from a guy that really knows these motors and he recommended an overnight seafoam bath.  I drove the car over to the workshop last night to go ahead and put the seafoam in and let it idle for a while and about halfway there it started running really rough and throwing a cyl 2 misfire code.  I gave it the seafoam treatment anyway and double checked that the injector electric was connected.  This morning I went back over and no change.  My next step is to mlclear the codes and move the injector to a different cylinder to see if the misfire follows it.  In order to do that, I needed a special tool - basically a slide hammer with a female 14x1.5 thread.  I have an old slide hammer and $8 later at the hardware store I welded up this:

Off to go check it out.

So weird: the side hammer adapter worked perfectly and I swapped injectors 1 & 2 but now the misfire is just gone entirely.  The ticking is still there so at least I'm just back where I started.  Interesting fact: it took a couple cranks to get the fuel back in to the fuel lines before it would start and when the starter is turning the engine over there is no unusual noise.  Kind of weird.

I got it apart and when I turn the crank by hand I think I can hear a noise coming from the valve train.  I'm guessing stuck lifter maybe.

I think the tensioner looks okay

I'd be more nervous about putting it back together without pulling the cams than I would be about putting it together without replacing the chain. That's my way of saying I'd pull the cams next. Any reported lifter issues on these? 

In reply to mazdeuce - Seth :

Yeah, the lifters are my primary suspect and I'm getting ready to pull the cams now.  I'm not aware of it being a known problem, but our friends in Stuttgart recommended a 10k oil change interval so some nastiness in there wouldn't surprise me.  I left the cams in so I could perform the "official" timing chain measurement check and I have way fewer than 11 degrees atdc movement on the crank pulley when I lock the cam, so that should rule out a stretched chain.  

I know that when a lifter makes a squish noise it means that the check valve is failed.  Should a hydraulic tensioner make that noise?  Mine is which could...  Oh..   hum.  That could make the chain slap around if it's gaining and losing tension.  Time to do some research.

Just got the tensioner on the bench.  I can compress it with one hand and it won't hold its oil.  Sounds fatal to me.

I'd replace it on general principle, but that's me. It it's thaaaaaat bad you can always just stab a new one in and see if that fixes it. Half day to reassemble. Five minutes to reevaluate if the sound is there and then maybe half a day to get back where you are?

In reply to mazdeuce - Seth :

That's what I'm thinking.  I'm getting pretty good at tearing into the valve train so it won't take that long to get back in if I'm wrong.  But it's where the noise was loudest and it takes almost no effort to collapse the tensioner so I think it's a bet worth taking.  While I wait on parts I can go ahead and pull the cams and check the lifters just to make sure.

The stack of parts from pelican arrived two days before schedule so I'm getting back in to it.  I planned to spend tonight cleaning up the head an the valve cover surfaces and taking care of the burnt wires.  Since the parts are here, I'll see how far I can get!

Crispy!

Wait what happened to the wires?  

In reply to dean1484 :

When I bought it, it turned out that for some reason the exhaust had been disconnected from the turbo and never actually reconnected.  I discovered this when I got a MIL for the swirl motor and for the fuel pressure sensor failure.  Turned out that the swirl motor and the sensor were literally melted.  Apparently there were also some wires that got burned up in that event as well and I found them when I was taking the valve cover off.

It blows my mind that a modern Mercedes can even operate without going into some sort of electronic seizure with those wires like that.