the1donald

Just bought my 1st Mercedes-08 C300 4Matic Lux. The car appeared near showroom cond. and had an impeccable Carfax history, w/only 1 owner and 47Kmiles. I have driven it less tha 100 and have simultaneous crank sensor and MAF sensor codes. I can deal with the MAF sensor, but the crank sensor has me worried, so I joined MB World in hopes of getting some info. When it comes to car repairs, I'd really rather do it myself.

bbirdwell

Search. Too easy. Crank sensor is a 20-minute job. Don't forget to perform a "flywheel adaptation" after replacing the CAS. Not hard and only takes a couple of minutes.

the1donald

Thanks for your quick reply, but this is a V6. The crank sensor is not visible except with a mirror and it is virtually impossible to get a wrench on it. Do you have some majick trick to share?

MJ50

moved to W204 forum...

xjmoe83

A 2008 Mercedes C300 crankshaft sensor pays 6/10 of an hour. It's a quick job.
Remove the air box, reach behind the block on the drivers side (in usa) and unplug the connector. Use remove the "inverted torx" screw and pull out crank sensor.

Removing the MAF helps some and I will say, its more difficult if there is a vacuum pump on the rear of the engine.

the1donald

Thanks xjmoe83 for the encouragement, but you have obviously never done a crank sensor job on this model/configuration. I have researched this job and found videos and threads posted on the web by others who have done it. As I indicated in my previous thread, the crank sensor is on the rear, drivers side of the engine. It's nearly impossible to get to and you have to go completely by feel as it is not visible without a mirror. The MAF sensor is relatively a piece of cake.

xjmoe83

Agree to disagree I guess. I guess through my 10 years as a MB Master tech, I haven't replaced a crank sensor on the rare c class w/272 engine. Good luck with the repair!

the1donald

It is my impression that this forum is intended for people to seek and offer advise. I appreciate any tips you may have to offer, but not your arrogance.

black lavender

These 08 4matics are trouble. I'm way too much money into mine to get rid of it right now. So many repairs.

EIS/ESL
Entire steering column
Thermostat
Small oil leaks

TheRulesLawyer

Dude, he's trying to help you. Might want to dial it down a notch.

FFM

Dude tells a MB master technician that he doesn't know what he's talking about, then gets mad when master tech responds with some mild level sarcasm.

The irony haha.

Thread derail, xjmoe83, you mind pointing me in the direction of the fuse for the wiper washer sprayer? As a former Volvo master tech something about taking a car in for a warranty inop complaint seems asinine without first checking the basics. It's a 2014. Dug through the manual and although they list fuse box locations, no fuse map, really?!

the1donald

Dude? Grow up! There were no helpful words, just a pompous monolog. I don't need a pompous "master mechanic" telling me how many standard hours a shop might charge to do this job. Have you ever replaced the crank sensor on this car? I am already dealing with a lot of problems that were caused and/or ignored by supposed "professional mechanics" at the Mercedes dealership. Please spare me any more condescending sarcasm.

FFM

I found the part where he described exactly how to fix your car to be quite helpful. But that's just me

the1donald

As I indicated in my 1st thread, I know where the sensor is. I also know what kind of fastener and tool. I also have removed the MAF sensor/meter and elbow to ease access to the back of the engine. And as I stated, the part is extremely difficult to get to and get a tool on, even with the MAF sensor, and elbow removed. It is a job done completely by feel as far as I can tell and according to others who have done similar jobs. The Mercedes shop has quoted $250 just for the labor on the job. That's $750/hr. according to our "Master Mechanic". I don't need anyone to tell me where the part is or what tool to use or to boast. I was hoping that someone might have suggestions on a better way to access the sensor. Sometimes it's necessary to remove a few parts or approach the job from beneath. It sounds like the some of the Mercedes mechs do it the hard way to, perhaps there is no easier way, and perhaps Mercedes is the most overrated car in the world.

dudeitsmattx

I would not say that MB's are over rated. There are just a lot of problems when it comes to the 4matic

the1donald

Can anyone tell me what is the sensor that's mounted next to the CPS on this 08 C300? It has a right angle connector. I am concerned because it is not snug and rotates with little force applied. Also, can anyone post a diagram and cross reference list of the sensors on this vehicle which would identify this and other sensors?

xjmoe83

Can you describe where the sensor is you are referring to in reference to this pic of the crank sensor?

the1donald

It's just above the crank sensor in that photo. It uses the same fastener(FM torx) as the Crank sensor. It is obscured by the crank sensor cable. I'm betting it's a Cam position sensor. Do you have any exploded view diagrams with descriptions? Thankx

xjmoe83

Hmm.. I am kind of guessing exactly what you are talking about but , I believe that is a ground cable. The cam position sensors are up front.

the1donald

Well, it has ~3 ~ 20 awg wires. I would expect a ground wire for the engine to be a large gauge wire, probably a flat braided wire. I sure wish I could find a diagram with descriptions. Thanks though for your consideration.

the1donald

Got it. It's a coolant temp sensor! Thanks to jpflip for postings on his previous thread.

the1donald

I finally got the crank sensor off and replaced. Fortunately, it wasn't on with very much torque and it came off relatively easily once I got a wrench on it. The MAF sensor/meter was a piece of cake. I reset the crank sensor successfully with the slow acceleration method described in someone's previous post. No more CEL! No MAF sensor code and no more crank sensor code! But it's not over. My OBDCOM tool still reports 0V for both upstream O2 sensors and the engine is idling rough and is a bit sluggish. I saw these voltages appear when the rest of the stuff blew up but was hoping that this was an anomaly related to the MAF and/or crank sensor failures. Does anyone have experience with this job on a 08-C300 4Matic or similar. I am debating on taking it in to a shop, but I have run out of $. Anyone have any idea why this car just blew all at once like this?

the1donald

Does anyone know why both the upstream sensors would go out simultaneously? Along with the MAF and crank sensors?

xjmoe83

Is it possible the crank sensor was the original problem and during its replacement the MAF (or vacuum hose) was not installed properly? This could cause a lean reading in your o2 sensors. I'd check for proper installation (seals are proper and connectors secure) and vacuum hoses. Also, how long are you waiting after you start the vehicle to look at the o2 sensor values? Is the vehicle up to operating temp? Is the coolant temp sensor accurate?

the1donald

Thanks for your input XJmoe83. The car ran fine for abut 200 miles. I had scanned the OBD before and after test drive before I purchased the car. The O2 sensors read ~0.45V. There were no codes and no CEL until the CEL illuminated and crank sensor and MAF sensors reported. At that time, the O2 sensors also read 0V from the OBD. The car was warmed up. I do wander though, about the condition of the air filters when I removed the engine cover to troubleshoot. The hose from the smog/air pump was disconnected and the air filters appeared to have never been replaced(it's an 08). I dumped about a cup full of junk out of the air filter housing. I could imagine how the clogged air filters may have caused the MAF sensor to burn out, and perhaps that condition may have taken out the O2 sensors as well. But the crank sensor to have failed at the same time is hard to conceive, unless, God forbid, that the ECU module may be taking out sensors. I have replaced the MAF and crank sensors and cleared their codes, but the up-stream O2 sensors still report 0V. The car is running rough at idle as evidence as well. I have stopped driving the car until I can replace the O2 sensors(can you say "have a nice Memorial Day weekend").
This is my 1st Mercedes. Everything that I know about them I have learned since I purchased the car a few weeks ago. I have read some bad reviews about the C300 on this forum. I am wandering if these cars have a history of bad ECU modules? I am also suspicious of all of the heat shielding in the engine compartment. With the splash panels underneath the engine and the heat shielding in the engine compartment against the firewall and along the wheel wells, it seems to me that there may not be enough ventilation and the sensors-O2, and crank sensors, may be enduring significant temperature changes and extremes, resulting in premature failure. I'm not sure what to think except that Mercedes may be the world's most overrated vehicle.
By the way XJmoe83, previously you had mentioned something about reinitializing the crank after replacing the sensor but you did not elaborate. I did try a method that I read about where you slowly increase revs over a couple minute period. This seemed to clear the CEL and extinguish the crank sensor code. But I still have a rough idle and 0V up-stream O2. Would you mind elaborating on the crank re-initialization thing?