Whining - Timing Chain? M104.098 1993 300CE

[johnathan1]

My first M104, and I noticed that when idling and driving it has a pronounced whine coming from the front of the engine. I tried changing the belt, tensioner assembly etc, but the noise persists. Gets louder when I remove the oil cap.

I know this car has an intake timing cam advance mechanism, but I've never had it apart and don't really know how it works. Is there something in this area that could cause a whining sound of this nature that wouldn't warrant replacing the timing chain etc?

I also should say that I have a Check engine light on and its giving me a code 18: Intake camshaft adjuster Circuit. The car also hiccups sometimes and loses power for no reason. Every part (literally) of the ignition and fuel system is brand new, except for the fuel distributor. Very well maintained car, with all maintenance up to date.

I realize that a worn chain and/or sprockets could cause this problem, but is there anything that could cause an issue like this that has to do with the intake cam adjuster?

Thanks

[oldsinner111]

I would examine motor first for metal flakes,probably oil filter.Whine can change because of loss of vacuum with oil cap off.Use a sethescope to pin point problem or long screw driver held to ear.Whine can come from alternator bear,pulleys,and acessories

[Rick76]

Sounds like it is a recent purchase? You say it is a very well maintained car but that doesn't mean that work was done properly. Do you have any records showing that the engine has been opened? Maybe the chain tensioner wasn't reset properly and the timing chain is too tight. Maybe the cam adjuster wasn't set properly.

Do you still have the original engine wiring harness?

[97 SL320]

Pull the drive belt and listen for the noise.

The cam adjuster is an engine oil fed piston that drives an inner / outer helical spline that allows the cam sprocket to rotate relative to the camshaft. Oil flow is controlled by an electromagnet on the front of the cam housing.

I'd at least pull the valve cover and look at the tensioner rails.

[johnathan1]

Yes, it was a recent purchase. I have brought it completely up to date maintenance wise. The engine harness is original and in decent shape. Car runs well, but "hiccups" every once in a while when trying to accelerate and has a flat spot about 50% of the time. Other times it runs perfectly.

I took a closer look and it looks like the timing cover was off recently, as it is very clean and it looks like silicone was gooped up on the right side where they often leak. I took the drive belt off and ran the engine and the noise persists. So it is definitely and internal engine noise.

Very strange

[duxthe1]

The only whine I've seen in these engines is an improperly installed timing chain tensioner. You can't just screw it out and then back in. The recent timing cover job sounds like a smoking gun.

You need to immediately pull the tensioner out and reset it before running the engine any further.

With the entire tensioner removed you remove its cap and push the plunger all the way out. Notice the circlip on the plunger. You want to insert the plunger back into the body until the circlip engages the first notch in the tensioner body. You then reinstall the tensioner body in the timing cover and torque it. You can now push the plunger in as far as it will go taking the slack out of the chain. Don't worry if there is a little slack in the chain still, oil pressure will make up the difference. Install the spring and cap last. Its tricky. I use an allen bit on a ratchet with a shortie ratchet wrench on the bit. You only use the ratchet to hold the cap in position and the ratchet wrench to turn it. Do pay attention to the soft aluminum seals, its easy to have them slip out of position and ruin them before even realizing it.

[johnathan1]

I've never improperly installed a timing chain tensioner so I had no idea a timing chain could make that noise. It made sense once I thought about it. Going to do the job tomorrow and get back to let you guys know what happened.

[Ferdman]

It's also possible the timing chain tensioner is faulty and needs to be replaced. That was the case with our 1992 300CE. To properly seal the timing chain cover it's best to use the MB black sealant that comes in a tube that works like a caulk tube. It's a great product.

The engine hesitation could be due to a faulty Oxygen sensor. When was it replaced last?

[Rick76]

When you have the tensioner apart, inspect the ring that does the ratcheting for wear. If worn replacement is 103 052 01 93. Also check the coil spring as sometimes it wears on one side and can become weak.
Good idea to change the closing plug aluminum seal ring as well especially if tensioner has been removed previously, 007603 020100.

Seals on the cam cover bolts tend to go hard as rock. You might want to add them to your shopping list if they are.

[johnathan1]

Oxygen sensor was replaced less than a week ago. Made no difference at all.

On a side note, I pulled out the injectors that apparently had been replaced about a month or two before I bought the car and I'm pretty sure they're original. -__- Terrible spray pattern and leaking like crazy on the bench tester. So I'm sure that's contributing! I've replaced every other part myself so I know it was done.

[johnathan1]

I should mention that I have also replaced the intake cam position sensor as well as the adjuster magnet and the check engine light and code persist. Any ideas? I'm out of them as far as that goes.

[johnathan1]

Reset the chain tensioner, much much quieter. I do believe that it was not reet last time and was far overextended. Amazing that it ran like that!

[johnathan1]

Should I expect damage from this mishap? It was driven about 250 miles before being discovered.

[97 SL320]

Inspect the timing chain rails, these are plastic / rubber and the first item to wear. The chain and sprockets are long term wear items.

Any idea why the tensioner was installed in a locked / extended position? Sometimes problems are induced when another repair is in process so finding the original problem is critical.

[johnathan1]

No, so far I do not know. I talked to the previous owner and she said that the car wouldn't run so she took it to a mechanic (who knows who) and they started "testing things". It looks to me like they only took the timing cover off, the air pump and the timing chain tensioner (who knows why)??? They then slapped it all back together and told her it was a bad EZL module.