I've spent hours searching these forums trying to figure out what might be making this sound, but I've run out of ideas and haven't found anything similar here or anywhere else on the Internet. I drive an '03 c320 coupe with just over 115,000 miles. This forum has been immensely helpful to me in the past ~2 years of owning the car, from helping me recognize the signs of my Valeo radiator failing just in time to save the transmission (dealership glycol test showed 400ppm+ glycol contamination in transmission fluid, torque converter lockup clutch makes droning noise and shifts kind of clumsy but works), to replacing the Crankshaft position sensor, along with a few other problems, so I'm hoping someone here recognizes this sound or can help direct me to some possibilities.

Anyway, now that I've gotten my introduction out of the way, here's what's happening with my car. Lately I've noticed a fairly quiet rattling/ticking sound coming from somewhere in the engine bay (more of a rapid and repetitive tapping sound which follows a definite cycle before repeating). I first noticed it after replacing my Crankshaft position sensor a month or two ago, but because it is so quiet, it could have been going on for quite a bit before I heard it. It's definitely not the EVAP purge valve, and I don't think it's the faulty A/C stepper motor because from my understanding, that sound seems to originate inside the car or dash. The sound is present from startup to shutdown, hot or cold, regardless of distance driven, and I THINK it may increase proportionately with engine speed (hard to tell listening from the drivers seat). It is quieter and more rapid than the videos I've watched for weak hydraulic lifters and other valvetrain noises, and doesn't seem to be injector noise. I've ruled out any loose plastic connections or other common sources of rattles and the only other thing I've noticed is that one of the belt rollers (not sure what to call them) seems to wobble slightly almost in time with the tapping. I'm going to try to take the belt off and run it for a minute without to see if it's one of the accessories being driven by the belt in the morning when I get off work, but in the meantime, does anybody recognize this sound? I love this car but as a college student working two jobs, I would like to figure out this sound before it becomes a major (expensive) problem.

Here's a link to a recording I took last night, I'll try to get a picture of the wobbling belt roller sometime tonight or in the morning as well:

http://vocaroo.com/i/s0IQzE2CiTvy

 

Try to wiggle the water pump. If it is loose at all it needs to be replaced. It is an job, but time consuming because of all the bolts.

 

My car made that sound or one very similar. See if it makes the noise with belt off.
If it doesn't record it again as I bet it is the same thing. Mine made it from around 120k (maybe before without being noticed) till I sold the car with 215k. I think it was a loose timing chain/tensioner on my car but the labor to fix was not cost effective so I was waiting for it to cause a serious issue.

 

Alright, so I finally had a chance to look at the engine again last night. Following Samaritrey's advice I took the belt off and made another recording, the sound was still present with the belt removed. Am I correct in assuming that I can rule out problems with the water pump since the noise was still there with the belt off? Here's the sound clip (Skip to 0:24):

Voice 012.wav

I'm fairly sure that the sound is coming from the timing chain/chain tensioner/chain guides, so I also pulled the passenger side valve cover to try and take a look at the chain. I didn't see anything that seemed terribly out of the ordinary, I wasn't able to manipulate the chain at all and the small portion of the chain that I could see didn't appear to be sagging. Is there a better way to get a look at the TC, without having to tear the whole engine apart?

Seeing as the m112/m113 engines have the double-row timing chain, should I be concerned about chain stretch? I can see how a single chain may eventually stretch, but the double-row chain on these engines seems pretty robust. Assuming that chain stretch isn't the issue that I am having, will a bad timing chain tensioner cause a similar sound? I've already gone ahead and ordered a new tensioner since they are fairly inexpensive and easy to R&R, but are there any other parts I should be looking at in case the new tensioner doesn't help? I really don't want to have to pay a shop to replace the chain or guides, is it feasible for these to be a DIY job?

Here are a few pictures I took while I had the valve cover off (please ignore the filthy, oil covered spark plug wires and engine, my valve cover breather gasket has been seeping oil for a year or two now):







Here's a close up of the chain, I couldn't see much further down than this, but the chain doesn't look like it is sagging to me, and I wasn't able to push it up or down where it leaves its gear and moves further down the engine.

 

Yeah its not the water pump sadly even though it sort of sounds like one.

There are a few of us around with this noise and I believe one person was thinking lifters (might have been something else it was a few months ago.) It sounds like a sloppy timing chain to me but who am I to say. I would check for stretch as even with double chains they can stretch..... Sadly my e320 with the om642 diesel just had to have its dual chain replaced due to stretch and making some really nasty sounds on start up that the tensioner could no longer account for.

Listing to your clip that sounds exactly like mine but mine might have been a tad louder than yours but its hard to say from a recording. As I mentioned before I drove my c320 extremely hard for around 100k with this issue and even put a tune on it lol and it never did fail. I figured that a timing chain job would be $2,000 at least and if it was something more serious it could be even more. So my plan was if it ever did fail I would get a junk yard motor with half the miles of the original and keep on going.

 

I guess I'll just have to see how it sounds once the new tensioner comes in and I get a chance to change it then, though it is a little bit relieving to know that your c320 made a very similar sound and didn't have any additional issues for so long. I tend to drive my car pretty hard as well, especially since having my secondary cats and resonator deleted. I haven't noticed any issues with hesitation or anything other than the occasional trouble with my torque converter lock-up clutch locking/unlocking abruptly since having the Valeo radiator issue last year. I was originally thinking lifters, but I figured the sound would be a bit less rapid than what I am getting from my car. I have also noticed that twice in the last week I was getting a very loud ticking sound on startup that seemed to repeat 8-10 times and was much slower than the current sound, but that goes away after about 10 seconds. That noise was far more like a bad hydraulic lifter needing a few seconds to get to proper oil pressure, but being intermittent it's hard to say exactly.

I also recently found out that my oil was 2.5 quarts low when I finally had a chance to check it on a flat surface. I had added a quart a week earlier, and another quart about a month prior, when the car requested it through the OSD in the instrument cluster and, not having a nearby level surface to accurately check the oil level, assumed that it was at or near enough to the proper level since it only asked for a quart, but I guess it was running quite a bit low for at least a month. I was a bit surprised to see how low it was actually getting to be, every other time in the past that I went below a quart low, the computer would warn me and tell me how much it needed. I guess I got too comfortable trusting the car's electronic oil level sensor to alert me when it needed oil, I'll be looking into purchasing an oil dipstick for this car soon if for no other reason than it being easier to check than finding a level area and waiting 30+ minutes for the oil reading to be accurate (not to mention the peace of mind knowing that I'm not just getting a funky reading from a bad sensor). Hopefully the oil wasn't low enough for long enough to cause any serious damage, but I'll definitely be looking for any metal flakes or other signs of damage when I get the chance to change the oil later this week.

 

Oh you're from NOVA what part? If you ever need star let me know.

My car also used/leaked oil anywhere from 1 quart every 1k to 5k and was sort of random. My rear main seal was leaking but obviously keeping some oil on hand was much cheaper than the repairs would have been.
I had a few members suggest that it was hydraulic lifters taking a minute to pressure up but as I said I never worried about it. I have heard some people have tons of issues with the electronic oil level/quality sensor but my 01 never had an issue. Also do you use dyno mode to read exact amount of oil? I have verified the readings and they were surprisingly accurate.

 

I live in Stafford, just a little bit north of Fredericksburg. I'll have to look into some information on Star programming, I remember reading about some cool features that could be enabled a long time ago. I do make sure to always check the oil level using the readout in dyno mode, it's too bad they didn't decide to make the regular oil level check as precise. I've been tracking my oil consumption/leak for the last week now since I saw how low it had gotten. When parking in the same mostly level spot at work, I've gone from a reading of 7.6 quarts to 7.1 quarts in 7 days/~400 miles (I can't say I've gone through exactly half a quart since the spot isn't totally flat and I don't park at the exact same angle each time, but having checked each night, I've been able to see the level drop from one day to the next). You're right about it being easier to just keep some extra oil in the car in case you need to top off, I can't say that it will be much more cost effective in the long run, but it's far more affordable for me to live with an oil leak than to fix it right now; my car has a funny habit of running fine when I'm broke, but having some kind of problem as soon as I get any extra money.

I just got an email last night from AutohausAZ, who I ordered the new tensioner from, stating that my order would be delayed by one day. I paid for the two-day overnight shipping hoping to have the part here today, but now it looks like I'll have to wait until Tuesday. When I do get the tensioner I plan to look for any other oil leaks besides the valve covers and valve cover breathers. From what I read, I plan to try and check for leaks at the oil pressure test cover, oil filter housing, camshaft expansion plugs, and rear oil level sender, as these seem to be the most common spots to leak on m112/m113 engines. At the risk of getting too off topic, are there any other common oil leaks that I should check for?

 

If I remember correctly (may want to check this) MB says 1L/1000km or roughly 1 quart every 621 miles.
If so then you are above that lol but something is not right as most don't use/leak anywhere near that much oil.

Oh the fun of Stafford got to love that traffic!!! I am just inside the beltway near Tysons.

 

Just a quick update, the new tensioner arrived on Tuesday, and everything following the arrival of the new part has gone entirely wrong.

Wednesday morning 12am to 6 am (July 1st)
To begin with, while removing the alternator to get access to the tensioner, I managed to break my finger by crushing it with the alternator when it pivoted down from the bottom bolt onto my ring finger (at 3am). Thinking that the alternator was going to be the last major hurdle and that I was on the home stretch, I soldiered on and removed the old tensioner without much issue. With the old tensioner out, I then attempted to install the new part, but found out after 2 hours of trying to install the new tensioner that the threads on the new tensioner were about 1mm further down the tensioner body than the threads on the original part. Being nearly 6am that morning, I decided to get some sleep and come back to it, but instead spent my morning at the emergency room because of the smashed finger.

Thursday afternoon (July 2nd)
Spent another hour trying to install the new tensioner, but ultimately ended up putting the old tensioner back in, however, the old tensioner was also extremely difficult to reinstall. Fearing that it may have crossthreaded, I backed it out and tried again with the same result 3 times, it required a ton of leverage to thread it all the way back in and I wasn't able to do it myself with just one good hand. I assumed that the pressure from the tensioner's spring pushing back against the threads was the reason that I was having such a hard time reinstalling it since it was the same each time after I backed the part out and then tried it again.

Saturday Afternoon (July 4th)
I had my dad come by and help to get the old tensioner reinstalled. I figured that since the tensioner body was so wide, if it had crossthreaded, it would have siezed up once it began to really dig into the aluminum timing cover, rather than continue to turn, but with great difficulty. Anyway, with my dad's help, the old tensioner was once again flush with its space on the timing cover, the alternator, belt, passenger side air intake duct, battery, airbox, everything else, was reconnected properly, and I was ready to start the car and see if by some miracle the old tensioner hadn't cross-threaded or anything. I guess there weren't any miracles left that day though, because as soon as I started the car I heard a spurting sound and the engine sprayed at least three quarts of oil out from around the tensioner in the 20 or so seconds it had been running. So much for the power of positive thinking. I should have known with all the misfortune I had already had with this part that things weren't going to suddenly work out for me.

Anyway, long story short, in the effort to preemptively prevent a potentially minor/potentially major problem, I crushed and broke my finger with the alternator, received a poorly machined/flawed replacement tensioner (OEM), and managed to completely crossthread the timing cover when reinstalling the original tensioner.

I read another thread on this or possibly one of the other Mercedes Benz forums about a mechanic who managed to do just about the same thing I did when trying to replace the tensioner on another members car with I believe the m271/m272 engine, but from what I read, it sounds like the m27x engines use a multi-piece tensioner which must be installed in a specific order, but the m112/113 engines use a single piece direct fit tensioner so I can't imagine why mine crossthreaded so badly immediately, unless the WIS was incorrect and I needed to disassemble the tensioner before installing.

Now I'm just wondering what my options are going to be. I'm going to have to have it towed somewhere, but I'm not sure what they will be able to do. Does anybody think it could be possible to retap the threads in the timing cover, or possibly even heli-coil the thing? I've found new timing covers for around $375, but I'm sure labor to replace the timing cover will be pretty high. The car has been pretty much rock solid up to this point, only really requiring repairs for parts that are well known to fail on the m112, still getting around 30mpg highway, and just running strong in general so I would really like to just get it repaired, but I'm working with a budget of just about $800-$900 and the new timing cover is going to eat up nearly half of that. I will not be taking it to the dealership for this work, since historically their estimates have been about 2.5x higher than a decent indy I've found in the area (plus they swirled my paint really badly about a week after I had spent 6 hours buffing/polishing my car when they provided me with a complimentary car wash during pollen season last year while testing for glycol contamination). I'm pretty disappointed in myself for letting this happen, especially since the car was running fine before I got all ambitious and decided to start fixing things that weren't necessarily broken, but I was enjoying learning what all the little parts of this engine do and how to fix them on my own when they go bad.

Luckily, I had requested all of next week off from both my jobs a few weeks ago to drive up to Michigan for a family reunion, so at least I'll have plenty of time to get everything sorted and get a couple of estimates. I'll keep this thread updated throughout the week as I get everything figured out, seems I'm the only one online who has personally managed to really mess up their timing cover/tensioner like this so maybe it'll help save someone else from making the same mistakes.

 

Hi. I know I'm over a year late on asking this, but, did you had any success on this case after that? Did the new tensioner solved the problem after all?
Any info will be greatly appreciated.