Over the weekend, the engine light came on in my C300.

This morning, I took it to the dealer to find out that it had something to do with magnets on the cams (of which there are 4 of) that control the valve timing. Apparantly 3 of the 4 of these magnets were replaced. I asked why they didn't replace the 4th one as it was pretty obvious that its time is short, and the service rep didn't know. I guess they're not allowed to replace what's not yet failed.

The CSR said that these magnets have something to do with valve timing which causes either a lean or rich mixture to occur if the magnets don't work.

Does anybody have any idea how that system works? diagrams maybe?

Also, I don't abuse my car. Why would these magnets go bad?

 

How many miles? At just over 20K miles, I had to have the Exhaust Cam Sensor replaced. Sounds a lot like the problem you had ... magnets.

I don't know why they would go wrong. If they're permanent magnets, they should be fine, unless something is reversing the polarity?

 

You probably had a code for continuous camshaft adjustment. The cam adjuster solenoids (magnets) become oil fouled. There are 4 of them, 2 intake and 2 exhaust. MB is replacing them with a new part number. They will only replace the magnets that set a fault code.

 

jstaneff,

Around 30,000 miles

 

is there a TSB for this?

 

skinny,

Since MB is replacing them with a new part number, can we presume that they know they have a problem and are replacing them with something better?

 

Yes they are, this is a pretty common fault on the 272 and 275 engine.

 

What vic said

 

So all those millions of miles of testing and this slipped past them?

 

The cars that are shipped arnt always a 100% replica of the test cars, subcontractors makes small changes and adjustments all the time, it would be impossible to predict all errors that can occur.

 

Vic,

Is it very likely that all three magnets would go out at the same time?

I'm wondering if it took the third one going out to get the engine problem dash light to illuminate. If that's the case, I'm concerned that the 4th magnet will go out and not activated the engine problem light.

 

They are cam position sensors and I would think that one going bad would give you a check engine light. one would throw a code. And I'm surprised that one wouldn't effect driveability if not cause the engine to stall.
Maybe they are redundant and you only use one intake/exhaust? Somebody know this?

 

The engine light might come on with only one faulty magnet as well, the engine light is based on the "severity" of the problem, for instance a specific number of misfires etc.

 

Only one time about a month ago when I exited the interstate and came to a stop at the bottom of the exit ramp, the engine loped, but when I got moving again it disappeared not to be seen of again. Otherwise, once the engine warms up its always been very smooth.

Does this provide any clues?

 

Very hard to tell, but a technician would be able to see in the cars fault memory what that was back then, if its not deleted that is.

 

Thanks vic

 

I would press the point of replacing three out of four.

 

Okay, I'm a wee bit confused. When the CEL came on, the manual (I stopped and looked it up, sitting in a forest glade ... ) said that I should drive the car to the nearest MB dealership for repairs.

Well, here's the confusion: what does this sensor control (ECS or ?)? Does it have anything to do with something that would cause great damage inside the engine? Or is it strictly fuel mixture, etc.? The manual said something about fuel quality, or the catalytic converter. I know the CC can be expensive, but I'm worried about damaging the inside of the engine.

And, does the CEL serve double duty? Is there ever a time when what it indicates should cause you to have the car towed?

 

I've just run into the same Cam Magnet problem. The diagnosis so far has them replacing the ECU, the wiring harness, the Oxygen Sensor and the Catalytic Converter for about $7000. My research has produced one document of interest regarding emissions related parts in the US: http://www.epa.gov/OMS/consumer/warr95fs.txt. The EPA requires warranty repair of all emissions related systems for 2 years/24000 miles and major systems (ECU, CC) for 8 years/80000 miles.

 

I just left the dealership today, had to drop mine off for the CEL, come to find out that this problem is an actual recall from Mercedes-Benz. So for those not tracking this, might wanna get yours replaced. the Cam Sensor Magnets, that is.

 

Mine is in right now because the CEL came on. Haven't heard from the SA yet so I don't know what the cause is. Got a 2010 as a loner, don't really like the new side mirrors they are so small.

 

At high speeds, pre-2010 mirrors are pretty noisy. In fact, I remember reading an article which stated that mercedes engineers admitted that it was the source of most wind noise.

I bet this fixed that

edit: I do admit I like the big mirrors though. Drove the e coupe for a few days this week and despite the lack of a b-pillar, I couldn't help feeling like the blind spot was huge.

 

My CEL was from a bad seal on the air filter box. The tech must have screwed up when he changed it at my B service.

 

I was orginally told the same(Bad Seal), when I took the car in, but once I went to pick up, they told me about the magnets. That there was a recall on them.

 

Do you need to remove PS res. and any other parts to get to the magnets on driver's side on ML350 2008?