So far in addition to bunch of plastic coolant pipes cracking because of age i gradually start having miss fires under moderate to heavy load (i don't usually drive this car - i have another S600 to roll, so once i have a chance driving GL consider it a heavy load). Scanner showed miss fire in both front cylinders - Cylinder 1 and Cylinder 5.
Normally it is a symptom of lack of fuel supply because of the most distant cylinders location.
To fix this issue i decide to swap supply fuel pump and filter combo in fuel tank.
Cons
1) No fuel pump access from underneath rear passenger seat anymore
2) Have to take exhaust, all the plastic and aluminum shields, driveshaft
Spend last weekend changing supply fuel pump. 20 dollar fuel tank wrench worked charming. Guess the outcome - nothing changed. It wasn't a fuel pump.
Next logical step was to change spark plugs. And here we come to another point of long discussed failure of Mercedes design.
Took off electric connector on Cylinder 1 coil. FULL OF OIL. What? Start pulling all other connectors on coils, sensors and so on.
Only 5 connectors had oil in it - 4 from camshaft sensors on top and one on coil in cylinder 1.
How this design failure works - camshaft sensors leaking oil from inside. Since all connectors weather (pressure) tight oil migrates through wire core all way around like through tiny hoses - still sound ridicules to me. After it reaches interconnect point in harness (Mercedes usually run ground or power on single wire with bunch of branches) it start flooding to other possible places.
Once it end up in other weather tight connector it start to mess with computer electronics (i presume from resistance in oil due to all metal contaminants)
Cure - Lots of brake cleaning sprays and compressed air to wash all the oil from connectors.
Which bring another question - will pig tailing work? Nope. If your pigtails are same weather tight type connectors - oil will still migrate through. Unless there is a solid interconnect exposed to environment.
Cylinder 1 misfire gone.
What about Cylinder 5? Clean connector. All good. Start pulling spark plug. Wait a minute. Some liquid on it. Taste like coolant. Yep from blown turbo cooling pipe some time ago. Swapped spark plug. Blowed hole around it. No more misfire on cylinder 5.

 

Great post, thanks for sharing this. Do you plan to replace the cam position sensors and cam magnets?

 

Cam magnets are not leaking - no need to replace. Cam sensors - i have a spare somewhere. Before changing those i am planning to saw spare apart to see where failure leaking point design. Otherwise no need to change old leaking sensors with new leaking sensors.

 

I also was surprised when I didn't see a latch under the rear seat, therefore I had to make one, I cut a hole. This is ridiculous, just to test the fuel pump harness or change pump I would have to take the tank down (insane amount of work).

I gently used a power drill and scissors for metal (not finished yet, just giving you an idea).

 

O.M.G.

 

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