The engine has done 107,000 km. It starts, idles and performs perfectly. Since about 90,000km I started noticing a ticking sound from the engine bay. During cruise at around 1500-1900 rpm at very light throttle openings it is a soft, constant ticking that does not seem to increase or decrease in volume regardless of throttle position. When I take my foot off the throttle, it goes away.
When the engine is cold, it is barely perceptible, and only really heard when the engine reaches full operating temperature at 90 degrees C. On a hot day once the engine is fully heat soaked on a fast cruise, it is a clear prominent tick that is heard above the radio.
The ticking is also through all the gears during acceleration, especially between 1500 - 2500 rpm which is the normal rev range.
It cannot be detected at idle and revving the engine with no load. It needs some load to appear.
Troubleshooting: I have removed All glow plugs to check for leaks. All ok and tight.
An independent trained Mercedes expert had the car for 2 days and checked the exhaust manifolds for possible leaks. He also checked the injectors on the testbook for correct fuel delivery. All found ok and within specs. He put the ticking down to 'combustion noise'.
I took the car to a second independent tuning and repair centre with good experience on the V6 diesel. They suspected a gasket leak on No. 6 injector. Nothing was found. They swapped no. 5 and 6 injectors and it made no difference. They returned the car with no fault found but admitted it to be abnormal.
I am servicing the car myself for the past 2 years after the maintenance plan has expired, but am using the MB oil from the dealers and GUD oil filters.
Please help - the car drives like a dream, but the ticking is really irritating, especially at night on a quiet highway when sound carries more.
My e-mail: AndreOberholster@gmail.com
Kempton Park, South Africa.
Tel: +27832996083

 

2012 GL350. 65000 miles. Same ticking happened like situation you described, under load (uphill) is obvious, low load (flat to down hill) is barely noticeable. All happened between 1500 - 1900 rpm. Chain adjusted by dealer 20,000miles/2 years ago. Wonder if it's engine knocking sensor kicks in and shut off incomplete burning cycle. or carbon buildup in cylinder well,and top. Any knowledgeable guru would shed the light? Thanks in advance

 

Hi komi999, my engine is a diesel - so there is no knocking sensor that can kick in. I have taken the car for a third opinion at an experienced large dealer , and after some very confused looks their suggestion is maybe a turbo shaft that could have excessive play (which I very much doubt) or, the swirl motor flaps, also known as the inlet manifold shut off motor flap that could have play. I have no engine warnings and the engine is very smooth right through the rev range.
I am not sure if your GL350 petrol has the same manifold flap system. Any other ideas from the forum? Thanks guys!

 

Hello guys, just some info on the ticking noise from the 642 engine (Diesel).

The ticking noise that you're hearing is most likely coming from the poly V belt or the big end bearing shells.... One extreme to the other!

Best way to determine this is to remove the belt first and run the engine briefly and see if the noise is gone or not.

If not then its most likely the shell, I think its on number 1 or 2 cylinder/piston.

As bad as it sounds it will not effect the engine/blow the engine up or cause any damage, its just really annoying to listen to!

​​​If you're wanting more info on this issue (or what I'm sure you're talking about) ask your main dealer to check for a TIPS document referencing the ticking noise.
PS its a mega expensive repair/rectification for a ticking noise.

Hope this helps
Jay

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That bill (end bearing) if not cures my OM642, it can definitely silence my ear and mouth... First diesel engine, but no luck to find similar discussion elsewhere, most of the talks in W164/X164/Sprinter are serious knocking than ticking under load. Thanks Andy, now I know there is no knocking sensor in diesel car. I am still trying to pint point the source of sounds. Going to remove combustion potential issue first, meaning easy fuel additive to see how it works. Under 2nd liquid moly purge treatment consecutively, seems better than 1st treatment. Will see if that's my problem after thousand miles.
So, Jay... the v-belt side of stuffs, how long those wheel bearing, idler pulley, tension pulley normally last? 80k, 120k? Thanks!

 

The idlers/pullys aren't serviceable parts, literally a case of replacing them! Tell tale signs are squeaking noises or squealing if they're seized (haven't seen any seize). I've replaced the belt tensioner on a 651 (220/250 Diesel) as it actually chucked the belt off it was that worn. You can check for play on the pullys if you remove the belt and pull up and down on them (like checking for play through a wheel) but even if there is no play, the component could still be defective.

Honestly though id just remove the belt and start the engine up, let it idle and see if the noise has gone away, will save you loads of time mucking about with additives etc and driving 1K to hope the noise goes.
If the noise has gone then replace the belt!

Start diagnosing with the easy possibilities first 😁

Cheers

 

Did the OP figure this out yet? I'm having EXACTILY the same issue. Almost sounds like the classic 'hole in a muffler' noise, but it's audible when brake torquing from the engine bay and certainly coming from the engine. It's not audible unless a load is applied: IE: not when free reving.

Only audible after engine has reached full operating temperature.

It's very annoying to listen to, bit doesn't seem to effect performance or drivability whatsoever.

First showed up after I removed and resealed all injectors due to black death.

I've already reset all adaptation data using DAS as well as check to make sure all injectors are programmed in correctly.

 

Hello guys. I have and Mercedes ML 350 Bluetec (Mercedes-Benz OM 642 LS DE 30 LA engine) and I experience the same noise. Only on load (especially uphill), between 1500 - 2500 RPM . Do you guys found what is causing this noise?