Hi folks. I have a 1993 W140 with the M104 engine. When the engine reaches the rpm for the cam advance magnet to be energized, I get a loud rattle, almost like when a lifter sticks (like marbles in a can). When I lift off the throttle, the noise goes away. I unplugged the cam advance magnet and the noise goes away. I also have poor idle and a running rich condition (however, this may be due to a bad O2 sensor...I am getting a code 22 on pin 4 (02 sensor heater open/short circuit) along with a code 24 (left camshaft solenoid open or short circuit) on pin 4 (38 pin test port)). I believe code 24 is because the fuse was blown for this circuit on the CAN BUS module. I tested again after I replaced the fuse and still get the same code, which is confusing because there is power going to the cam magnet. I have driven the car a couple of days and need to retest to see if the code is still there. Bottom line, plugged in it the noise appears when the cam magnet operates (around 1,500 rpm under load, and 3,000 rpm when the engine is revved at idle, which is correct), and when unplugged, there is no noise, the car idles rough but drives smooth, although sluggish, obviously.

I've replaced the plugs, wires, cap, rotor and coil, and I replaced the cam magnet solenoid.

Any ideas on what's causing this noise? I don't believe I have a timing chain issue. The car runs fine (other than being a little sluggish due to no advanced timing, and the rough idle problem) and drives very smooth down the road.

I'm really at a loss as to what to check or how to diagnose. I thought about pulling the cam magnet off of the car, starting the car and manually pulling the cam sleeve that the magnet would normally pull forward to see if the noise presents itself. I believe this sleeve is pulled to allow oil flow to change, advancing the left camshaft.

Finally, the only other thing I can think of is replacing the cam position sensor on the side of the head as I have read this can affect how the ECM causes the cam magnet to operate. I've always though the cam position sensor either works or doesn't with no in between, but I had a Ford Ranger act up where it would cut out under heavy load and it was the CPS. I hate to keep throwing money and parts to a car but I'm completely at a loss.

I hope someone else has an idea! I've posted on two other MB forums with no response at all.

Thanks!

Here is a recording of the sound. You can hear me getting in and off of the throttle...the noise mimicks a machine gun. When I’m in the throttle you can hear the noise.

https://youtube.com/shorts/0_AE4fayOwU?feature=shared

Sounds like the engine ain't running Post a link to a youtube video.

Working on the early M104's can be a *****. It was available in just three models and only from 1991 till '93. Parts are expensive and hard to find.

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).

Was the head gasket replaced recently? Maybe the timing timing is incorrectly set and what your hearing is valves hitting the piston slightly

Was the head off recently? Maybe cam adjuster set incorrect and what your hearing is pistons lightly hitting the valves

No, I do not believe the head was off, but I am not certain. I guess I'm going to have to pull the timing cover (I believe it's leaking anyway...something is leaking oil pretty consistently) and check the timing. The car just runs so well (other than the idle) and it cranks evenly I just can't believe the timing is off, but I'm out of ideas.

Doesn't sound like metal on metal to me and the frequency is to high, I've heard solenoids make that kind of sound.

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).

Kind of sounds like metal on metal in person, but I’m not sure. It’s a brand new solenoid from Mercedes and makes the same exact noise that it did with the old solenoid on it so I don’t know. I’ll post another video with hopefully a little better example of the sound.

Here is a longer video where you can hear the tap/noise as I accelerate. The noise stops around 11 seconds into the video when I let off the throttle a bit and maintain cruising speed.

https://youtube.com/shorts/dqJqdkndMsE

And here’s a link from the garage tonight. I guess there’s something off with the timing. I’ve looked all over the internet and I guess I’m the only one that’s ever had this problem.

The little rattle you hear at the beginning is the tensioner making a little noise. It’s definitely a metallic sound when I rev the engine and the solenoid is energized. So I guess I need to check the timing chain to see what’s going on. Thing is I don’t know what I’m doing with these so I’m not sure what I’m looking for. Could be something wrong with the advance sprocket or system. Again not sure I know what to look for.

https://youtube.com/shorts/8IkQ288Pbsw?feature=shared

If anyone has any further ideas please let me know.

Don't worry about it, its the sound of the cam actually advancing. They are not terribly quiet engines.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

When your putting the chain on the adjuster for the intake cam the adjuster must be rotated fully right (clockwise)and your marks (o lined up with the top of the head-------) as per assembly instructions, if your timing is off it will rattle on acceleration, I'm a mb tech 36 years

This is beyond just a slightly noisy engine. The noise is very loud and the engine boggs down when the solenoid is energized.

So if someone had the timing chain off and didn’t set the intake cam advance correctly to the retard position it would cause this noise? So sounds like I need to pull the timing cover, tensioner, loosen the chain, set all to TDC with dowels on both cams lining up with the machined surface, turn advance section of intake cam to the right, and reinstall the chain with slack towards the tensioner side and then reinstall the tensioner. Is this all correct?

Also, for resealing the timing cover, I need the U shaped green gasket and some copper Permatex for the gasket ends. I assume I will also need the O-ring for the cover as well, correct?

Finally, I am unsure how to reinstall the tensioner, but I am sure there are directions as it doesn't sound hard. Any advice is appreciated.

Is there anything else that could be causing this noise? I thought about pulling the solenoid, starting the car and pulling the adjuster shaft forward on the cam to see if the noise is present. But, I’m sure it’s not the solenoid making the noise as it’s new from Mercedes and the old one did the same thing.

Nulu, I received an email notification that you responded, but when I come to the forum your response isn't here. Nevertheless, I posted video clips of the noise above, but here they are again. I appreciate your help. I plan on tearing into the timing cover this weekend and check to see if the timing portion is in the correct retard position at TDC, and if not, reset it and see how it goes.

First video in my garage: The rattle you hear at the very beginning is the tensioner that I need to replace. The loud noise that I posted about is heard when I rev the engine to 3K RPM and back off slightly: https://youtube.com/shorts/8IkQ288Pbsw?feature=shared

Second video while driving: You can hear the noise as I accelerate and when I let off the throttle the noise stops and the engine sounds normal: https://youtube.com/shorts/0_AE4fayOwU

Once again, when I unplug the cam advance magnet solenoid, the engine is very quiet and smooth (other than at idle) and runs "ok" on the road other than being a little sluggish obviously.