Strange sounds coming from on603 - PeachParts Mercedes-Benz Forum

Mt2385 · #1 01-26-2022, 11:33 AM

https://youtube.com/shorts/sAGV2PCzxf4?feature=share

Does anybody happen to know what the intermittent strange sound is coming from this engine? It’s coming from the front of the engine where the timing chain is. Only does it at idle. Runs great

JHZR2 · #2 01-26-2022, 11:50 AM

That is a strange one. Sounds like something shaking around.

Id look for loose bolts. I have a bolt with nut that is at the intake round side connector. It spins in the bore. It can make a shaking sound sometime.

Is the radiator fan shroud multiple parts? If its two parts, are all the nibs pushed and locked in?

Are any fuel lines hitting the intake?

What is the status of the tensioner? The shock (be careful, it can get super hot) and the spring can break. If the shock is good, the spring might break and rattle. Ditto for the status of the tensioner pulley and idler pulley?

Have you used a mechanics stethescope, or a screwdriver, or dowel, and tried to listen to the vacuum pump? The bearings an go bad in there and rattle around. One thing recommended to me was to run with the belt off for a short time to see if noise is coming from something belt driven. This was before GP replacement, tensioner shock replacement, etc., so now the engine is much smoother and quieter, even at stone cold frigid weather (which was the condition for this video):

https://youtu.be/8_0kdJ0oySI

oldsinner111 · #3 01-26-2022, 12:18 PM

try crank pulley bolt, more like damage vac pump

JHZR2 · #4 01-26-2022, 02:05 PM

Quote:

Originally Posted by oldsinner111

try crank pulley bolt, more like damage vac pump

Agree that is the biggest concern, thus the need to run with belt off and see. The tensioner and all can make a lot of racket...

87tdwagen · #5 01-26-2022, 07:19 PM

Try getting a mechanics stethoscope scope or long screwdriver to help pinpoint the source. It could be a timing chain guide loose or ovaled, or any of the aforementioned suggestions above. An oddbal one you can check may be a cracked EGR accordion tube also in that same general area. Really hard to guess at this one. Good luck

JHZR2 · #6 01-27-2022, 09:59 AM

Quote:

Originally Posted by 87tdwagen

Try getting a mechanics stethoscope scope or long screwdriver to help pinpoint the source. It could be a timing chain guide loose or ovaled, or any of the aforementioned suggestions above. An oddbal one you can check may be a cracked EGR accordion tube also in that same general area. Really hard to guess at this one. Good luck

Have you had luck with a stethoscope on these engines? There are so many clicks and clacks and noises that its hard even when something is noisy, to pinpoint.

I like the recommendation by Barry to remove the belt. That helped me a lot....

87tdwagen · #7 01-27-2022, 10:10 AM

Quote:

Originally Posted by JHZR2

Have you had luck with a stethoscope on these engines? There are so many clicks and clacks and noises that its hard even when something is noisy, to pinpoint.

I like the recommendation by Barry to remove the belt. That helped me a lot....

I think removing the belt to isolate any belt driven components is a good suggestion.

Regarding the mechanics stethoscope, I think it is invaluable, you can check individual injectors for nailing, delivery valves, even helps find ticking lifters, helps locate noise to specific areas by comparing against other areas. Once you become accustomed to how things should sound, pinpointing the odd sounds become easier. Cheap investment that saves time in diagnostics. Get the stethoscope rather than a long screwdriver, it is more precise and by having your ears plugged you are really only hearing what the stethoscope is touching.

Mt2385 · #8 01-27-2022, 10:44 PM

Thanks to everyone who have suggestions. I basically checked everything mentioned and more and started to think it was coming from the motor. Then I discovered it was the shock side of the tensioner. Intially, I only checked was the spring side, which was good. Thank god. 😅

Appreciate all the input

87tdwagen · #9 01-28-2022, 09:40 AM

Good that you found it and it was the tensioner shock. Now remember that sound, because it will be back again soon. A known downside is that the shock bushings fail fairly quickly, some outfits you can source just the bushings as they fail exceedingly fast as compared to the shock itself which can last quite a long time.

JHZR2 · #10 01-28-2022, 10:32 AM

Quote:

Originally Posted by 87tdwagen

Good that you found it and it was the tensioner shock. Now remember that sound, because it will be back again soon. A known downside is that the shock bushings fail fairly quickly, some outfits you can source just the bushings as they fail exceedingly fast as compared to the shock itself which can last quite a long time.

Does anybody else’s shock get super hot to the touch, like burning hot, even when new?

I recall learning this the hard way on my 91 w126 a few years back. But the shock was done for.

On my 93 I just replaced the shock with a new stabilus one, and the tensioner is silent and works great. But it also gets burning hot to the touch because of the dampening and the vibration rate.

Is this normal? Engine is smooth and quiet.

87tdwagen · #11 01-28-2022, 04:35 PM

Quote:

Originally Posted by JHZR2

Does anybody else’s shock get super hot to the touch, like burning hot, even when new?

I recall learning this the hard way on my 91 w126 a few years back. But the shock was done for.

On my 93 I just replaced the shock with a new stabilus one, and the tensioner is silent and works great. But it also gets burning hot to the touch because of the dampening and the vibration rate.

Is this normal? Engine is smooth and quiet.

Yes, effectively it is mounted to the cylinder head and the timing cover via the tensioner, so it will be at engine temp in short order. I have found that the top bushing tends to fail the soonest, it is also the one closest to the head/engine and likely gets cooked a little sooner than the lower. Sometimes wrapping a split rubber hose around the body of the shock so as to contact the head will keep it from rattling quite a bit and extend its usable life.

cmac2012 · #12 01-28-2022, 09:22 PM

It’s a little depressing how much more user-friendly the serpentine belt tensioner is on my ‘89 Chevy van, 5.0.

The OM603 tensioner does work and is an interesting piece of engineering but...

83w126 · #13 01-31-2022, 12:17 AM

Quote:

Originally Posted by JHZR2

Does anybody else’s shock get super hot to the touch, like burning hot, even when new?

I recall learning this the hard way on my 91 w126 a few years back. But the shock was done for.

On my 93 I just replaced the shock with a new stabilus one, and the tensioner is silent and works great. But it also gets burning hot to the touch because of the dampening and the vibration rate.

Is this normal? Engine is smooth and quiet.

Is the bearing in the tensioner (where it's bolted to the timing cover) still good? I believe installing a one way alternator pulley would help also.

compu_85 · #14 01-31-2022, 10:53 AM

I had the *identical* sound coming from my 350SDL. I thought it was the vacuum pump or timing chain. Spend hours trying to figure it out.

The problem ended up being the bearing in the belt tensioner arm. Several of the balls had fallen out, and that sound was the tensioner arm knocking against the timing cover.

The shock should not get burning hot - but they tend to. I had 2 shocks get so hot on my SDL that they'd puke their oil out.

I'd highly recommend you install a clutched pulley on your alternator. Get the one specified for an OM606. I installed one on my 350 (along with a larger alternator) and the difference is dramatic.

https://www.youtube.com/watch?v=DGI9XLuhaYY

EDIT: Found an old video I'd taken which shows the sound: https://www.youtube.com/watch?v=puFCqJbIk3k

-J

JHZR2 · #15 01-31-2022, 11:37 PM

Quote:

Originally Posted by compu_85

I had the *identical* sound coming from my 350SDL. I thought it was the vacuum pump or timing chain. Spend hours trying to figure it out.

The problem ended up being the bearing in the belt tensioner arm. Several of the balls had fallen out, and that sound was the tensioner arm knocking against the timing cover.

The shock should not get burning hot - but they tend to. I had 2 shocks get so hot on my SDL that they'd puke their oil out.

I'd highly recommend you install a clutched pulley on your alternator. Get the one specified for an OM606. I installed one on my 350 (along with a larger alternator) and the difference is dramatic.

https://www.youtube.com/watch?v=DGI9XLuhaYY

EDIT: Found an old video I'd taken which shows the sound: https://www.youtube.com/watch?v=puFCqJbIk3k

-J

The brand new stabil us shock on a very smooth 603.971 gets super hot. Never seen them lose oil though…