OM602 Periodic, Precisely-Cycling Knock/Tick. Has anyone experienced this before?
 

I looked/searched and couldn't find anything for this specific issue- feel free to redirect me if I missed it. I'm hoping someone has seen or heard of this before and can at least help me narrow down where to look so I can track it down. It's odd.

My 1991 300D, OM602, 130k, runs beautifully, but has a very precise, periodic tick that cycles at nearly perfect 18-second intervals. From the moment the tick becomes barely audible, it spends almost exactly 10 seconds building in volume/intensity, then goes silent for 8 seconds

Stick with me here, I know it's sometimes futile to describe sounds over 'net, but I'm giving it a go anyway: So it's not audible, becomes softly audible, then "tick-tick-tick-tick-Tick-Tick-Tick-Tick-TICK-TICK-TICK-TICK-TAK-TAK-TAK-TAK-TAK," then suddenly silent again for 8 seconds. The interval is about 3-per-second at idle. After the 8-second silence, the noise builds again for 10 seconds, goes silent, and so on. Happens cold or hot. I'm clueless

If it were an injector, or maybe valve noise, it would be pretty much constant, correct? What the heck would cause a periodic cycling knock/tick?

Sounds pretty much like my lifter tick on my 87 300d. Does the noise go away when you increase rpm with a warmed up engine?

Difficult to say with all the elevated noise at higher RPM. Seems to diminish, though, yes.

EDIT: If it were lifter noise- why would it be so precisely-timed? I mean, I can sit there with a stopwatch over a period of minutes and it doesn't change. 10-8, 10-8, etc.

The first thing I'd do is remove the serpentine belt. Start the engine and run it for a minute or so (don't worry, it will take awhile to overheat). If the noise goes away, it's related to the belt, tensioner, or rotating components.

If the noise is still present, then remove the two hoses from the vacuum pump and run the car again. If the noise goes away, replace the pump pronto.

If the noise is still present after removing the belt and vacuum fittings, then my money is on a lifter. Perhaps it's periodic because the lifter is rotating.

I like this, Mxfrank. It's logical and has a good process of elimination. Thanks!

The Vacuum pump had occurred to me. The noise, at least to my way of thinking (which is admittedly not always on-target) could be associated with something building--->releasing vacuum, maybe? Hopefully not, as it seems the rebuilt pumps or rebuild parts are becoming very hard to find. Seems like it's better to just throw $$$$ at a new pump if problems arise with the old one.

Will proceed this weekend and report back.

A video or sound clip of something like this would be VERY beneficial in trying to diagnose what and where to look for!

Indeed. :) Just got back into town last night, and will probably record it while running Mxfrank's procedure today.

I plan on running a diesel purge today as well to see if that affects anything.

1991 timing chain/sprocket issue?
 

1991 300D 2.5 Turbo cars are covered by the TSB detailing the defective/sub-standard timing chains and the eventual premature sprocket wear. A careful examination of the chain and the cam sprocket would be in order particularly if no other obvious source of this noise is not readily identified.

If it persists after checking the hother belt drive, loosen the injector lines one at a time to see if you can isolate the ticking to a cylinder.

Sixto
83 300SD
98 E320 wagon

I don't think that's correct (unless there's a second TSB of which I'm unaware). The TSB on defective timing chains on that engine affected a certain range of serial numbers in 1993.

See posts 14 and 15 of this thread for details.

http://www.peachparts.com/shopforum/diesel-discussion/56836-93-2-5-turbo-timing-chain-replacement-interval.html

Video is Up!
 

I ran a can of Diesel Purge through it and changed the primary fuel filter. Seems to have dampened the noise maybe a bit, but that could just be psychological after the purge, etc.

Anyway, video of me noise is here.

You can hear it pretty clearly at starting at this timestamp.

Could be that I was incorrect remembering exactly what model years and range of individual cars that TSB covers. According to the post you've referencedit would be cars built in 92 and 93 July 92-July 93, not just 1993 cars.

But I would point out that the TSB info in that thread is at least 13 years old since it was posted on the forum so there might be another TSB that has come out in the intervening years since that was done.

I would also put forth the other pertinent info from a few posts earlier than the TSB info.

post # 5:

"I just today looked at a "'91 300D Turbo - Blue, 178K mi, 40K on reblt eng, CD, sunroof, maintd, all rec. $7500".
Nice car, but the reason for the engine rebuild was the timing chain broke. "

post # 8:

"I have a 91 300D 2.5 with only 77K original mileage. I checked the chain for stretch a couple of weeks ago and was astonished to find that it currently has 5 degrees of stretch. This measurment was taken using the factory procedure at 2mm of valve lift, not the old "line up the marks" approach. I'm really surprised at this amount of stretch since the car came with records indicating oil changes every 4-5K miles.

I did look up the factory recall on the 602 chains - it was in a Star issue a couple of years ago. As I recall it applied to early versions of the 602.962. My 91 model was NOT in the recall so I can say that maybe you should at least check the chain for stretch since it would appear that at least some examples of this engine DO seem to have chain stretch issues. I also agree with Sixto, I have heard (second and third hand) about some chain failures with 602 engines.

I'll be doing the chain in my car as soon as I can get the time.

Tim "

So I wouldn't put all too much faith that no cars except those covered by that TSB might experience such a problem!

My point was that these 602 engines in some cases have been known to exhibit timing chain problems, being that the original poster was looking for information about what could cause the noises he described it seemed prudent to mention the possibility of a timing chain issue.

You can get a cheap "Mechanic's Stethoscope" at Harbor Freight that will allow you to listen to individual engine components and isolate just where a particular noise is emanating from. You can touch the tubular probe to a particular component and hear the difference between that location and others.

You can do things like touch each injector and hear them to find a noisy one, place the probe against the intake and exhaust manifold openings and hear any difference between one and the other valves opening and closing.

You can use the same technique to listen to the various pulleys driven by the serpentine belt to find a noisy accessory's bearing noise such as an alternator or AC compressor, as well. The Stethoscope only cost 3 or 4$ last time I bought one.

well, my 93 had a tick like that, I can't remember how intermittent it was though, I think it was worse hot. But in the end it was lifter tick due to oil pressure to the head. I replaced all my lifters and it still ticked after that (I don't think they needed replaced). I kept driving it with the tick. Eventually my head gasket blew, the gaskets on theses engine will push over and block the oil port that feeds the head and block oil flow thus lowering oil pressure to hyd lifters. They push between the number 1 and oil galley. I would tend to bet it could be this. If this is indeed happening you want to catch it before it blows because it can damage the aluminum head by gouging it at that point, that's what happened to mine. Anyways if you think it is an internal knock like that and not a fueling knock I would just do a head gasket. I believe there are other post on this problem try searching it.

There was another case of OM602 noise on this forum years ago that was solved by changing the two o-rings on the oil filter tube. Very strange. I don't think that noise cycled like yours, however. Cheap and easy enough to try.

Update
 

Well, I found this thread, which seems to match my noise exactly.

Still a bit of trouble shooting to do, but I suspect strongly that I have hydraulic lifter noise. I have to pull the valve cover to check timing chain stretch, anyhoo, so will check lifters/cam at the same time.

Now, the big question, what is the root cause of the lifter wear, if it turns out to be lifter wear?

I'm starting to lean towards the idea that jltcasper3 brought up. Might just be the head gasket beginning to fail and obstructing oil passage/passages.

There is a bunch of stuff I plan on doing anyway (fuel filter, coolant flush, another oil change, probably will do the pressure-wastegate mod, thermostat, preventative vacuum pump renewal), so I think I may just pull the head and change the gasket as a preventative, as it does leak a bit of oil, and it seems gaskets on this vintage of M-B are sort of notorious for ****ting the bed at regular intervals (I had a '93 190E that needed a new head gasket about every 60k).

Will photograph stuff and report any findings.

Something else to check: inspect the camshaft, gear, and timing chain carefully. There was another case of a camshaft key missing that allowed the camshaft to float fore and aft, with some weird noise I think.

Wouldn't a compression check reveal if weak / oil starved lifters were not fully opening and allowing full compression?

Pulling the head just to diagnose a noise is a bit extreme.

Pulled the Valve Cover
 

... and checked timing chain stretch. That can be a little nitpicky. Thanks to good help from threads here, I figured it out, and discovered that I only have about 1.5-2.0 degrees of stretch. Seems fine there.

Warmed the engine and then turned through per FSM procedure to check hydraulic valve actuators. 5 of the 10 showed noticeable movement/drop. So it now sounds like I have to inspect passages feeding the hydraulic actuators for contamination. And I guess replace the actuators while I'm at it. So off comes the cam soon. Lobes seem fine, with what I'd consider normal wear for a 130k car. No gouging, grooves, or oddly uneven wear that I could see.

I think I read somewhere that there is a plug on the rear of the head you can pull and then blow compressed air through the passages feeding the valve actuators in order to clear them. Will have to search for that again- unless anyone knows off hand where to find it.

Unfortunately, from what I read here, I may have a failing head gasket, as noted in previous posts. What else could clog up those actuator galleries?

Additionally, I noted a good bit of blowby while running the engine (had the breather pipe disconnected during warmup) and there is a noticeable flow of crankcase gasses under pressure coming from the breather. That's a little off-putting. How much is normal?

Which hydraulic actuators were weak? If the back cylinders, than yes I would also lean toward a clogged oil passage. If they are random, then maybe not.

When I installed a head on my OM603, I left the camshaft off, and all of the hydraulic actuators removed. I suspended the timing chain on the camshaft gear with a 1/2 inch drive extension (or maybe it was 3/8?). I think all the injectors were also out, so no compression. I stuffed a rag at the first camshaft bearing oil feed under the drive extension to block that oil "leak", and then used the starter to rotate the engine and pressurize the oil galleries. After a good few seconds of flow at each hydraulic actuator hole, I installed them from #1 to #6, waiting at each hole for pressure to build and oil to flow so that I could verify good flow and flush out the oil passages.

You could do something like that to check the flow / pressure at each hole.

It is also possible to take apart and clean the hydraulic actuators, and avoid the expense of purchasing new. Number them by location so you can put them back in their original holes.

If your blowby is severe and random actuators are flat, that may point to poor maintenance - too long between oil changes - which leads me to believe that carbon clogging of the rings and the actuators is the issue, NOT a failed head gasket.

In answer to your question regarding blowing compressed air through the plug at the rear of the head to clear the oil passages yes it can be seen in the picture of this link.

https://www.google.ca/search?q=mercedes+602+head+pictures&prmd=isvn&tbm=isch&tbo=u&source=univ&fir=4QUMuIoih6_hMM%253A%252 CVlKZNX3xCS-6uM%252C_%253BAJedEYW4ggObPM%253A%252CVlKZNX3xCS-6uM%252C_%253BMcbEYWUYFrKHDM%253A%252CrdU5ywV_12JHAM%252C_%253BmwO_VWaAvDT_4M%253A%252CH_oc5Pcvae-c3M%252C_%253B7FCw3oCTSaWUuM%253A%252CbsZTnJ0CCY6o1M%252C_%253BEr-Cx_BYV3M2UM%253A%252C8ijr1iYSKH8WkM%252C_%253BcxGWnCrIiNxGmM%253A%252CxvhEBki8hPZPtM%252C_%253BnoOVJ v_CMB_FeM%253A%252CabQb3Srs0y6KqM%252C_%253BTnAXtd1bdDXxqM%253A%252Ckykl1XjALW3iUM%252C_%253B2Jwy8kV BBJ-qsM%253A%252CxvhEBki8hPZPtM%252C_%253B9P3NwHtuCjpJaM%253A%252C4jUgwTeLCp_-4M%252C_%253BbgSGq7c9tXHr4M%253A%252CIPn8bsihCZEcpM%252C_&usg=__YNi0Edk9WSfiyy9lYkVXyhRn3HI%3D&sa=X& ved=0ahUKEwj8iJOOle_SAhVE-mMKHTjVAAMQ7AkINg&biw=589&bih=371#imgrc=C6C2Hzj7o9snnM:

I believe the head needs to be removed limited room to acess the plug and the cam also needs to be removed to allow any contamination to fllow out.

Maybe time for a compression and leak down tests.

Collapsed hydraulic lifters are fairly common. Before pulling the head and putting at ton of extra work into this engine that you don't need to, try disassembling them and simply cleaning them. Keep them marked which positions they go back into so you don't ruin your cam.

While it's all out, the port to blow out the oil galleries is in the rear corner on the driver's side. I believe it's an 8mm bolt point directly back at the firewall. Very limited clearance. On my 603 (with 12 collapsed lifters) nothing but air came out of any of the oiling ports when I pressurized that passage. The lifters WERE full of varnish and muck though. Cleaned them out and have several thousand miles on them and they're all silent.

ALL diesel engines have blowby (all engines in general have blowby, but diesels have a bit more than their gasoline counterparts). The higher the compression and the higher the miles (or wear), the more they have. With the engine hot and at operating temperature, the general "test" is to loosen the oil filler cap and let it sit on the filler hole. If it's bouncing you have excessive blowby (not to say it's time to rebuild the engine just yet). If it blows off the hole or is dancing around on the valve cover, it's just about time to do a rebuild.

ticking noise OM602 engine
 

have also a W124.128 with about 135K. Engine made the same or a very similar noise at idle. Timing chain was changed when cyl.head gasket was replaced and I also installed the upgraded vac. pump. Therefore I also suspected the hyd. lifters. Stetoscope confirmed noise was coming from the top, middle of the engine. Bought new lifters but did not fancy the job and they are still in my basement. Switched engine oil to Shell Rottela T6 and after driving a couple of thousand miles ticking disappeared. Just my experience.
Did use 15-40W regular Rottela before with shorter than recommended oil change intervals.
Cheers

Ordering/numbering the 10 actuators from front to rear they were: 1, 3, 7, 8, a teeny little wiggle on 9, and 10. 10 was the worst of the bunch.


Saw some info on that. May give it a whirl. Cost isn't too much of a factor, though, and using new may save time. I'm on the fence.

That's certainly good news. 2nd owner didn't change oil as regularly as the first. But then again the car was only driven ~7k miles over a period of about 10 years by the second owner. It seems to have sat quite a bit, which isn't good either. On that note- what's a good way to try to clear possibly-stuck rings? I'm in agreement that a compression/leakdown test may be required soon.

Perfect, thanks. Fortunately, front and rear clearance with the 5-cyl engine is pretty darned good. I think I can reach that plug without much issue, hopefully.

So, stupid question time: Would that quick test be performed with all the breather apparatus still connected (breather tube still feeding the turbo inlet)? Or would I need to remove/block the tube for a correct assessment? With everything connected, I can observe blowby gasses when I peek into the valve cover, but the pressure doesn't seem to be enough to push the oil filler cap around when it's just loose in the hole. When I had the tube disconnected from the turbo inlet and briefly plugged it with my finger, there was definitely enough pressure to immediately push the cap off the hole.

The breather tube should still be connected when checking for blowby pressure. There will ALWAYS be positive blowby pressure in the crankcase, so if you block the breather, you will pressurize the crankcase (these cars don't have a flow-through PCV system like the gas engines).

My SDL has enough blowby to fill the valve cover with mist/smoke, but not enough to move the cap.

If you car sat a lot, you may have varnish/sludge issues on top of what you already know about with the car. I certainly had some NASTY garbage come out of my engine (sat for 10 years in a field). Oil filter housing was full of something akin to pie filling, bottom of the sump had something similar to jello in it. Nasty, nasty, nasty. After 3 oil changes and an engine "flush", the oil is back to being oil again and the engine is much happier. Oil consumption went from 1.5 quarts every 500 miles to less than 1/2 quart ever 2000 miles and still improving.

I'd suggest just cleaning out the lifters you have (you may be surprised [and repulsed] by what you find in there [the smell is truly appalling]) and running synthetic oil for a couple of short-duration oil changes to clean out all the "crap" that's likely collected in there.

Easy: Switch to Mobil 1 synthetic oil, give it some time to clean up the carbon (thousands of miles).

A little harder: fill each cylinder with Marvel Mystery Oil, let that soak for at least a day, change oil before driving.

Compression tests before and after may help confirm that you're making progress.

Personally, I just use the M1 oil and stop worrying about it.

any update?

As for me mine did this tick, especially after a hot freeway drive, and then sitting in a drive-through. When I got around to it, I adjusted the "too soft of a shift(s)" at my transmission modulator due to flaring, and not only did the shifts tighten up, but the throttle response and the tick disappeared to. It's almost as if when you have a vacuum source hogging the pressure, that it makes other things go weird as they are all tied in somehow.

Freak thing, not sure if coincidence, but that's a lot of symptoms to go away suddenly.

My 2 Euro cents...

1: Find the source of noise with mechanics stethoscope before disassembling anything.

2: if it does end up being tappets don’t bother cleaning them. Get a new set. They are inexpensive.