SLK55NEWB

My symptoms Apologies in advance for layman terms

1. Car would have difficulty igniting the engine after driving the car for about 10 minutes. The starter would turn but the engine would not fire.

2. Car engine would stall and either start back up right away or #1.

3. #1 and #2 were intermittent but progressively became more consistent over time


Problem: Suspected Crankshat Position Sensor. Mercedes Parts had a label on the part that referred to it as Sender Unit. Costs was $138. Any parts guy will know the part as this is pretty common.


Tools needed

1. Small to medium sized right forearm and hand. The angle of the sensor points 30 degress so you have to access it from the driver side of the car. The space between the passenger compartment and engine compartment is pretty tight.

2. The attached pic shows me trying to use a socket wrench with a 24 inch extension and an angle extension. It was actually easier to use a socket screwdriver as this helps you keep from losing the screw.

3. Torx 7 socket - I bought a Torx socket set from local auto parts storefor 20.00. Make sure you dont buy a torx bit. It will be a socket.

Instructions
1. Hardest part for me was to find the sensor. Even with a flashlight you can barely see it. It is located directly behind the engine in between the passenger compartment and the engine. It will be just right of the center of the engine and points at a 30 degree angle to the right.

2. Pull back the heat sheath to expose the sensor plug. It will have atypical clip where you must squeeze to detach the plug.

3. Using the torx socket and feel method, locate the torx screw. It should be underneath the plug. Unscrew and try to keep the screw from falling. It fell for me once and luckily went all the way through.

4. Reverse the steps to install

5. I took this from another posts but it said to rev the car above 3000 rpms for 60 seconds.

6. no more stalls. Congratualtions you saved yourself about $300

Cheers

AMGSpartan

Hey thanks for the TORX socket info. I struggled with the screw on my sensor this weekend whilst changing the tranny fluid. Due to the angle of the sensor, you can't see the screw itself. I abandoned the project as I couldn't get a proper purchase on the screw. I'll have to get the right socket...wonder why they couldn't use a 'normal' screw.

Spart

taurran

Just attempted this, but was unable to find the correct TORX socket. There is no such thing as a "TORX 7" socket from what I could see at the auto parts store. It must be something bigger.

lowprofile

You need an E-torx size 8. E=external
To remove the plug, grab the clip on the North and South sides, squeeze and pull.
I would suggest removing the airboxes for some additional room.

taurran

Thanks man, after looking at some of the W210 forums I figured it was the E-8. I'm not sure where this guy go the "torx 7" from, but it was too late last night for me to run out to a store and get the E-8 socket.

I'll get the socket tonight and give it another go.

One thing, I have big hands and its hard to get down in there. Ended up cutting up my hand yesterday trying to get down there. I think I need to find a stubby socket driver, or else hacksaw one of my current ones so it's short. Hmmm...

shardul

iTrader: (1)

Nice DIY. Now what is the sensor behind the idler pulley on the front of the engine is it the Camshaft positioning sensor.

taurran

Just tried this again today. Getting to that bolt is impossible unless you have the hands of a 12 year old girl.

I'm not even sure if the E-8 socket is the right size. I thought I had it on for a minute but it felt like it was just rotating freely around the bolt.

I give up.

Infiniti

I did this a week ago, i simply just removed the little rubber outlining thing that the hood closes on or whatnot. It is a torx i cant remember what size but i used a swivle and a couple long extensions, i barely was able to get my hand down there and i put the socket on the bot and held it and had my brother loosen it up as i was holding it. If you can get a socket screwdriver thats probably going to be the best way. It can really **** you off becasue its a tight fit but it can be done! when i pulled my sensor out, it almost looked like oil on it but it was dirty, any ideas?

izzyz28

I know this thread is old, but I have some useful info I want to share.

First of all, as soon as you notice there is a problem(car randomly dies and may or may not restart), go buy the part or get it ordered. My car died a total of 4 times in about a week's time. The first 3 times it fired right back up, and the 4th time I was stuck on the side of the road for half an hour. Do NOT wait and risk getting stuck in the middle fo the road somewhere.

Secondly, it is a very cheap and easy fix. I got a new Bosch sensor for ~ $60 shipped to my door from Pelican Prts, and it took me less than half an hour to install.

All right, now it's time for some install tips. First order of business is to remove the airboxes. It takes literally 20 seconds, so just do it. With the airboxes removed, not only can you see the sensor,but even a person like me with giant sausage hands can actually fit a hand down there to remove/install the sensor.

You will definitely need an E8 1/4" drive inverted Torx bit. I also used a flexible 1/4" extension(plus another solid extension), which allowed me to guide the bit onto the head of the bolt with one hand and gave me a pretty straight shot from the bolt to the ratchet, without the risk of a universal joint doing funky things and dropping the bolt. I loosened the bolt halfway, the pulled the sensor up a bit to help capture the bolt once it was free. When reinstalling, don't forget that the bolt goes in at a pretty good angle, so don't crossthread it.

There is really no magic to it, just remove the airboxes, get the proper tools, and you'll be set. Or better yet, bring it over to my house, pay me $300, and I'll have it back to you in two days for that dealer experience.

Turbo 6

I'd like to add a tip as well. When re-installing the torx bolt, take some electrical tape and wrap around the base of the bolt and barely on the socket. This will ensure you don't drop the bolt when threading it in. I found there was no way I could get my hand in there (once the new sensor was in) and start threading the bolt.

tbal

Also, just something to add point, make sure you put the hood up to the maximum possible raised position by pull on the tabs near the hinges, it will allow for more working room. Its a PITA to get at, but beats paying the stealership couple hundred.

izzyz28

In my excitement I forgot to add that. What I did was place the bolt in the sensor and then install the sensor/bolt with my finger keeping the bolt in place. I then installed the sensor most of the way but left it far enough out so it would hold/support the bolt. Once I got the bolt started, I pushed the sensor the rest of the way in. Normally I do use electrical tape, but I wanted to try it this way. Take your time and save the aggravation of a dropped bolt. I cannot fathom how anyone could start the bolt by hand without dropping it about 10 times.

Edit: If anyone in the Chicago area would like help with this and wants to travel to Bolingbrook I'd be more than happy to work with you and show you how it's done. Same goes for light bulb replacement or any other simple to do once you've done it once but seems intimidating at first jobs. PM me if you're interested!

lightningfast7

Great thread. Just finished replacing mine and saved over $300.
I would definitely pull the airbox. Takes less than a minute and makes things a whole lot easier. Entire procedure only took 10 minutes. Thanks.

xterra18

save my life guy, nice DIY instruction

zeus1

i just did this on my car. it took 30 minutes, nice write up.

dvdt

It took some of you guys less than an hour?!?!?

I just pulled intakes and airboxes and still cannot get at that damn thing, i can barely even see it!

turbo97se

Are you on the right side of the car? It's a 15 minute job

alihou007

30 min!! 15 min!!! Wow...impressed. I just did it couple of weeks ago and took me an hour after I got all the right tools...Main challenge is you need arms of a 10 year old kid and feels like you are working blindfolded. And....doing it slowly as you do not want anything to fall in the bay.

E55Freak

first time was about an hour but i could probably do it in less then 30 mins now..

turbo97se

I have small arms but the right size where it counts

DogEars

Wanted to say thank you for this information, took about 20 minutes to do the whole job and I only sliced the top of my hand once getting it down in there.

Panduh

I think I'm going to do this as a preventative measure.

Does anyone know if you have to do a re-learn for the crank sensor after you put the new one in? Also, do I need a star tool to do this?

I know I've had to do that on a older GM 6.0l

Crissus

No relearn procedure for a crank sensor. Never at any MB car thats older than "start stop technology"

Panduh

Thanks!

Z06Tom

Just as an FYI, a standard 1/4" socket also fits the bolt. I just did mine and didn't have a torx.