In reply to mazdeuce - Seth :
I'll admit that I find it hard to believe that the car that tracks and reports on the temperature of the freaking steering wheel is cool with basically all these wires rubbing their nasty bits against each other. I'm hoping that this solves the O2 sensor heater shorted to positive code that it popped at some point.
Following the think twice wrench once philosophy, I may have found the problem? Two of the rockers on the exhaust cam looked like this:
The retaining clip that holds the lifter into the rocker arm is loose and there's a ton of play between the top of the lifter and the arm. Could it be that simple?
I crimped that clip back and put the cams back in. Fun fact: they have two sets of timing marks on the sprockets! So hopefully I chose the right ones and I'm not 180 degrees off.
Good news: I got the cams back in correctly.
Bad news: the problem was neither those clips nor the tensioner.
Took the belt off to rule out the water pump, compressor, power steering, and alternator. Still ticking.
Bear with me while I think out loud a bit here. Here's what I've been able to test and verify so far:
Here's what I think might be true:
Here's what is unsure:
And finally, wild theories:
If I was dealing with a Chevy, I might be a little more willing to put a giant magazine into my parts cannon and start firing, but apparently the German rounds are a bit more expensive so I hesitate to open fire just yet. I'm tempted to throw a chain at it, but between buying the special chain tool and a chain, that's a pretty big nut to risk on a guess. I guess the upside is that if it is the bottom end, I'd want to put a new chain on it anyway as part of the rebuild. Right now I'm pretty stumped, but I think my next steps are:
EDIT: Another 2 thoughts: First off, I bet I could thread my stethoscope down through the oil fill to try to get a better listen at things. Also, I wonder if I took the head cover off I would find that those clips on the rocker arms were loose again. I'm really thinking it's timing chain, lifter, or The Bottom End.
Primed and reinstalled the tensioner. No joy. Still can't really tell where the noise is originating. I'm completely out of ideas at this point and beyond frustrated. I guess I'll either put a new timing chain on it or take it somewhere and have them perform a walletectomy.
This sure seems valvetrain related. Did you take the cams out of both heads or just the one that the noise seems louder from? I'm guessing it's a complete bitch to get back in there and redo any of it but if you're still willing to throw time and effort at a fishing expedition you could just swap the entire set of lifters/rockers between the heads and carefully inspect all the rockers in the process. If you don't find any rocker problems but the noise follows the lifters, buy one head worth of lifters and voila. 20hrs later it will be fixed! Or stare at every lifter in that head until you come up with a way to narrow down the culprit. That's a very labor intensive guess so I won't blame you for ignoring this idea!!
Is there anyway to shut off the injectors and have some one crank the engine while you look for the sound? I am assuming the normal rattle of the diesel is making it hard to find. It sounds like a slap to me. If not in the valve train then maybe a wrist pin.
In reply to Vigo :
Well, you bring up an interesting point. I only poked around on the side that I think probably sounds loudest. Also, the right side is much easier to get in to than the left side. So this might be like the drunk guy looking under the streetlight for his keys because the place he dropped them is just too dark. At a bare minimum, I should open up the right side again and see if the retaining clips on the rockers have come apart again. Lifters are about $12 each and the rockers are $16, so I could replace all of those plus the chain for just under a grand. I imagine that would either fix it or rule out the top end of the engine. Unless it's the diesel pump.
In reply to pjbgravely :
That's one of the weird things: When it was re-filling the fuel filter, fuel rail, and injectors, it cranked without firing for 4 or 5 intervals. It doesn't make that noise when it's just cranking. Only once it starts. Maybe it's just too quiet at 300 RPM or whatever to hear it from the side of the car. I do know that when I turned the crank by hand with the head cover off, I heard an intermittent clicking/snapping/metal-on-metal sound that was coming probably from somewhere in the right valvetrain.
I'm getting pretty fast at opening up this valvetrain. The right side, at least.
It looks like the clips on the rocker arms are still in place. I was hoping against hope that it might be that simple. I do need to verify that I have the exhaust cam in place. When I took it apart, I didn't realize that each cam had two timing marks 180 degrees away from each other. Why would they do that!? I don't hear any piston-valve banging (and it is an interference engine) but it is running poorly so it's possible the exhaust is out of time.
Not that it had anything to do with the ticking, of course.
720 degrees of crankshaft rotation which actuates every single valve once. And I'm picking up an audible click every time the cam is at one certain point. I can't tell where that click is coming from, but I get it every single cam rotation at exactly the same spot.
Here's a tech tip for the solo wannabe mechanic: I set up my GoPro to record as I turned the crank a few times and then cranked up the volume on my laptop and played it back. Those metallic sounds seem to really jump out on playback, more than to my actual ears and then I could play it back to see exactly where the cam was each time.
EDIT: I'm 99.9% sure that the noise is coming from the left bank of the valvetrain. I pulled the diesel injection pump off the head to see if it was the source, but no change in the noise and the pump turns smoothly. The problem now is that they put everything on top of the left side head cover. Like, everything. So, plenty of work to do to get everything off the cover so I can get the cover off the cams.
I'm not ready to dance the dance of joy just yet, but I took out the lifters and rockers on the left bank intake cam. Still getting a tap when I turn the crank pulley. Took out the lifters and rockers on the exhaust cam, left bank.
No.
berkeleying.
Tap.
So one of six lifters, rockers, valves, or valve springs. I'd say that narrows it down a bit, eh?
Seth, thank you for continuing to remind me that even if it's from Stuttgart it's still just an engine. And diesels just clatter a lot and don't have spark plugs.
Vigo, your direction appears to be spot on, thank you!
I'm not doing a victory lap just yet: just because I was hearing this noise with the engine turned by hand doesn't mean it's the noise I was hearing with the thing running. There's a light at the end of the tunnel that stands a decent chance of not being a train, though and I'll take that!
Put the intake rockers/lifters into the exhaust side. The first couple rotations, there was a click but after that, no noise.
So, put all the rockers/lifters back in but swapped the ones for cyl 4 and 6. If the noise happens at a different time, it's one of those. Otherwise, it's cyl 5. Probably. Except now the noise is gone.
Plan: buy 6 new lifters and replace all the left bank exhaust lifters, put it back together, and see if that takes care of it.
Sounds like progress! I can't give myself much credit for my suggestion because all it was was a grueling path down the road of process of elimination. If i was able to come up with something that would have saved you the 10-20hrs i'd be proud!
Either way, you like the car enough to fix it, you rejected defeatism, and you are closer to success of your own making than you were yesterday. So far so good!
Lifters came in on Monday, but I didn't get too far that night because I wound up not spending the time I should have cleaning and prepping everything else over the weekend. Because of that, I spent Monday night doing all of that work and actually dropping the new lifters in and re-installing the cams on the left side.
I was a little confounded by the right side, however, since it doesn't look like the timing is where it "should" be. Basically, they have two sets of dots on each cam gear which are situated 180 degrees from each other. One is a mark at the tip of the tooth and the other is at the valley. In the center, where the two gears meet, the tip mark for one cam is supposed to match up with the valley mark from the other. Because there is a locating pin on the intake cam for the timing sprocket, I can be certain that the intake cam is not 180 off. The other mark on each cam is supposed to be basically level with the surface of the head. The left side marks are all spot-on. The right side, however, is a little bit higher. To the point that it almost looks like it's a tooth off. When I had the timing sprocket off initially I was unaware that there were two sets of marks so I only verified that the tip-valley meshing marks were lined up before removing the cams - so I have no idea if that position has changed at all. I did secure the chain to the sprocket to prevent the chain from moving so, in theory, because of the locator pin, the intake came could only have gone back to where it was before, right?
Last night, Tim came over and helped me work through that exercise: We pulled the cams again, popped the timing sprocket off, marked the chain & sprocket, and moved the chain over one tooth on the timing sprocket - working under the possibility that the chain jumped a tooth because I didn't have it tied down enough. After putting it back together, it was pretty far off (by at least a tooth and a half in the other direction, possibly two teeth), so the operating theory now is that it's where it needs to be. But I still don't know for absolute certain. Guessing that we got it right, I put the Loctite on the head covers and put them back on the heads and got the left side injectors greased up and re-installed.
Another variable is that I do not have the "special tool" for holding down the cams -- instead of using cam caps like the rest of the world, they deviated from the normal plan of "why use one good part when we could engineer fifteen precision-fit parts" and incorporated the cam caps into what any other car would call the valve covers. There are little hold-downs on each cam, but when the lobes are sitting on valves, it takes a bit of pushing and levering to get the cam low enough to hook the hold-down into place and thread its bolt. So, it is possible that with the special tool, I'd be able to set the cams perfectly and the slack would come out of the correct side of the timing chain path? I alternate between belief that is absolutely what's going on and belief that it is absolute crazy talk and physics don't work that way. I did get a sample of Trex decking, though, that I originally planned to use a hole saw to put a cam-sized hole in, cut in half, and then drill bolt holes through so that I would have my very own special tool that wouldn't risk scratching up the cam. Maybe the idea of building that isn't so nutty after all.
At this point, though, you're thinking: "But, Bill! You've already put the thing back together. It's too late to go building that tool, you fool!" But, see, that's where you're wrong. You've fallen victim to one of the classic blunders, the most famous of which is never get involved in a land war in Asia. But only slightly less well-known is this: Never underestimate my ability to screw something up in a new, exciting, and utterly inconvenient way! As I was putting injectors in, I came across three small bolts sitting with the injectors. Strangely, those bolts looked just like the ones that I installed back into the timing sprocket, fastening it to the camshaft. Oh, berkeley. I mean, those bolts that I was supposed to have installed back into the timing sprocket.
So, I am going to have to take the head cover off again, clean it up again, install those bolts, and then put it all back together. Again. The good news, of course, is that without those bolts, the sprocket would come off and almost assuredly completely grenade the engine so I'm really glad I found it now. In fact, I'm chalking that up to the results of prayers for the intercession of St. Eloi (the patron saint of mechanics) and would be willing to consider that a literal miracle. That said, I do now have an opportunity to assuage my neurosis and build the special tool to hold down the cam and try, yet again, to see if I can set the cams and then get the timing sprocket to attach and hold the cams closer to the relative position of the left side and what WIS seems to indicate I should be seeing.
I'm not going to lie: This thing where Mercedes uses Loctite 5970 instead of a head cover gasket is getting on my nerves in a big way. I suppose it's not so bad if you only ever have to do it one time in your life, but with the third re-installation of the right side head cover it's starting to get old. First, you've got to use a slide hammer to pull the cover off which isn't that big of a deal, but it requires the manufacture of yet another special tool. Once it's off, there's goo on both faces that needs to be scraped and brushed off which means acetone, rags, a brass brush, and a Formica sample chip to use as a scraper. Once that's done, you've gotten particles of dried sealant and potentially bits of brass bristles all over the place, so you've got to wipe all that down and vacuum it all out. Then, when putting things back together you have to coat the cams and their bearings in oil, but the mating surfaces have to be absolutely clean and free of oil, so more rags and acetone. The Loctite is expensive stuff and has to be applied with a caulk gun in a specific pattern across the head cover. And finally, the cover has to be dropped straight down onto the head within 10 minutes of the application of the sealant, being very careful not to smear the bead of Loctite. And then there's the three-step torque process to install the 30 bolts.
So yeah, I went ahead and pulled everything apart again the other night after I spent about 3 hours making a new special tool. This tool is the equivalent of Baum tools 642-0031 which seems to retail for about $50. Their tool is much better than mine, make no mistake, but I'm some combination of stubborn and stupid (stubbid?) so I went off to make this thing. To be a little more fair to myself, when I decided to make the tool, I wasn't aware that it was available at a reasonable(ish) price.
Knowing that this was going to be a one-time use tool, I wanted something that was easy to work with and wouldn't run the risk of putting any scratches or whatever into the cam or head. I settled on using a bit of Trex decking since I figured the composite material would give before the metal of the cam and I can work it with saws and drill presses that I've already got around. Turns out that at my local Home Depot, they have a whole bunch of scraps of composite decking in their lumber cutting station that they give out at no cost as samples so the material cost was $0.
After setting up my radial arm saw to be an inverted table saw, I cut the decking down thusly:
Having never actually worked with this stuff before I learned my first lesson: Most of the strength is found in the outer layer which peels off kind of like a sticker. I guess it's some sort of chummed-up plastic fill encased in a plastic laminate? Again, never touched this stuff before, so didn't know what to expect.
Anyhow, I went ahead measured up where the bolt holes needed to be and used the drill press to put those in.
Putting the holes for the cams was more challenging than I expected. First of all, despite measuring about 8 different times, I still managed to get them off a bit, plus the hole saw was burning and melting more than cutting so I went in multiple stages, taking my time to push the hole saw through.
I ran that through the saw again to cut it in what was supposed to be half, but again, despite multiple measurements I must have set my fence wrong and wound up a little too much to the left on my cut. Whatever.
It took a little bit of work with a sanding drum, but eventually:
These would not measure up to any type of daily use. I suspect that they will be good for about 5 uses before they crack, split, and have to be thrown out. But I was able to use them to rotate the cams to where the marks were right on the edge of the head and then pull the cam to the valves by tightening the head cover bolts through the hold downs. The way that I made them, they need to be used with a slightly longer bolt than the head cover uses, but the important part is that they worked! Previously, I had to sort of lever the cams into place a bit to get the little hold down clamps in place, but this time they were simply pushed down through the clamping force. Once the cams were in place, I put the hold down clamps on (easily, I might add) and then got the timing sprocket re-attached and put the tensioner back in.
After all of that, I am actually not sure if it made any difference at all. I thought I had "before" pictures of how Tim and I had it lined up, but I guess I was only thinking about getting pictures, not actually taking them. Here's where it is now:
(And with this post I have now increased the number of pictures of OM642 timing marks on the Internet by about 100%)
I think that it looks slightly closer than it was before, but that might just be me not wanting to admit that I spent four hours to just get right back to where I started.
Now I just need to get everything buttoned back up and see what, if anything, I've managed to accomplish.
Good news! It's timed correctly and the idle is very smooth.
But it's still ticking.
In reply to wae :
I'm an a-hole for laughing at that, but I did.
I agree with the loctite as well. Horrible stuff.
So it's all apart nothing ticks, but when it's running, not starting, tick? These are hydraulic lifters, yes? They're pumped up by oil passages in the head? What if the lifters are fine and you have an oiling issue?
Just spitballing here, I really have no idea.
In reply to mazdeuce - Seth :
No, it really is just funny at this point and I actually was rather relieved that at a bare minimum I haven't made it worse!
There was a noise on the left bank that seemed unusual, and it's not making that noise anymore. But I can only assume that whatever that was it was inconsequential. With the six new lifters, it took just a second to get them pumped up on the initial start and that noise was much quieter than the ticking that I'm trying to solve. So that's interesting.
I won't rule out an oiling issue - I'm not 100% sure how all that works. I'm not getting any sludging or anything like that; the oil actually looks really good.
The next thing I'm going to check is to do another, more thorough search for exhaust leaks.
Can't find any exhaust leaks. I counted the rate of the ticking and I'm coming up with a pretty solid half-engine-speed rate. Screams valvetrain to me, but berkeley if I know. I guess I'm going to have to give up and take it somewhere.
Can the valves themselves make noise? A broken spring or something? I'm just throwing stuff out there because honestly I have no idea. You should drive it to the Challenge so we can all stand around and listen to it.
I suppose taking it on an 800 mile road trip to the challenge would likely solve the mystery - but likely because it would grenade itself on the way there :)
The valvetrain noises that I hear when I turn the engine by hand are not staying consistent right now. Previously, there was an audible click from the left bank every time the #1 intake cam lobe got below the edge of the head. But that noise is gone now, with an occasional click that sounds like it's from the right side now. I checked every rocker arm and didn't find anything that looked loose or broken. I looked at each valve spring to see if any were broken, but they all looked and felt fine. I'm not saying that none of those things are broken, but at this point the only way I can see to troubleshoot them would be to just replace all the valves, springs, keepers, rockers, and lifters and that's a pretty expensive shotgun shot.
Well, I have officially thrown up the white flag. I have an appointment to drop the car off at the local M-B dealer at 1530 today. I spent last night with a giant sheet of paper on the wall and a Sharpie, writing out everything that I thought could possibly be causing the problem and so on. Didn't come up with any new ideas.
Irritating backstory: When this first happened, my initial guess was stretched timing chain. That's like "the" issue with these motors. So, I called the local independent shop and explained that the car was making a ticking sound, I suspected the timing chain, most likely (at the time) didn't want to buy the special tools to do it myself, did they have experience with the OM642, and could they give me a rough order of magnitude estimate for what a basic timing chain replacement would run me. "Oh yeah", they said, "the owner's wife drives one of those and he just did the timing chain in her car, so we can do that." I was promised a call back with an estimate.
The next time I talked to them was about a month later when I called them this morning. I explained what I had and that it was making a ticking sound. This time, though, I wasn't 100% sure that it was the timing chain since it seems a little slower than the typical timing chain sound that I've heard, but I was hoping they could tear into it and find out what was making it tick. After a little back-and-forth they presented a plan wherein I would take the car to the dealer, have them diagnose it, and then I could call the indy shop back with the Official Gold Plated Mercedes Diagnosis that they would then use to give me a competitive quote on the work to actually fix it. As a bonus, maybe they'll finally have the replacement airbag(s) that they can install for me while they have the car.
Which, is basically what I asked them for once before and never heard back.
I realize that I'm probably the biggest nightmare customer for any shop, so I can get why they probably don't want to deal with me. But knowing that and liking it are two wholly separate things :)
Apparently the dealer has lost my car. I'm assuming this is a rather temporary situation, however, I called them at about 0900 today and they said they were going to send out a search party. Still haven't heard back... (A) They didn't bother looking for it, (B) They found it and didn't bother to call me back, or (C) They have now also lost one or more of their service employees.
I did have it sent in on a flatbed instead of risking driving it, so I assume that the guy didn't drive directly past that dealership and go all the way the heck up to West Chester... I assume that if he had forgotten to drop it off he would have had another call-out by now and realized that something was on his flatbed.
I always get the weird ones...
This is the best mystery on the internet and it just got better. I love this thread.
Hooray! It took them 24 hours (and me giving them the VIN. Again), but they found my car!
But now they've lost the key.
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