Okay guys, this is my feeble attempt at an Alternator DIY.

Please keep in mind that I was actually swapping out the alternator whilst trying to remember to take pictures, so if a step wasn't well documented or all together left out, please feel free to leave feed back! Doing it this way, I can remove and replace my alternator in about 45 minutes.

Just basic tools are needed, a 3/8 and a 1/2 ratchet, universal swivel joint, 10mm socket exernal torx (e-sockets) sizes E12 and E14 a nromal torx bit size T60, a couple of 3/8 6" extensions a 8mm and a 13mm wrencha flat head screwdriver.

Now to get to the bottom alternator bolts, you can very easily get to them from undernearth the car, but if you are lazy like me and want to do everything from the top side, then you will need a 1/4 inch ratchet, a 2" 1/4" extension and a 1/4 - 3/8 . With this setup, its pretty easy to reach to bottom bolts from the top. Looks like this:





First things first....Using a 10mm socket remove to battery cover and disconnect the positive terminal.





Next we are going to remove the air filter housing hose and connections at the front of the car and where it connect to the housing. (I am actually missing the hose but you can see where to connectors have been removed):





Next we are going to remove the hose that runs from the silencer to the EGR valve (I think it's the EGR, let me knoe if its not!) remove it from the top side:





Now we are going to disconnect the silencer. At the lower side, we are going to use our flathead and pop out the clip that locks the lower hose into the plastic silencer. Once it is popped out the we can slide the lower hose out.



Once it is out, just slide it back and use the side of the cooling fan to hold it in place, out of the way, like so:



Next we are going to unbolt the silencer from the block. there are 2 bolts, 1 upper and 1 lower holing it in place. You will need to use the E10 socket and what ever set up you can to get to the bolts. For me, I used my 3/8 ratchet with with a 6" extension and my swivel on the upper bolt and I used my 1/4" ratchet with extension to reach the lower one.

Once you remove the 2 bolts, use your flat head scredriver and unbolt the clamp for the hose that connects to the upper section of the silencer and once the silincer is completly loose, just let it fall. It will be out of the way.

Now that the silncer is out of the way we can release the tnsion on the belt and remove the belt. You might be able to get away with using a 3/8" ratchet, but I used a 1/2" ratchet so I could have leverage to move the tensioner easily. So You will need a T80 to do this, you will find the "hole" for the socket to fit in on the lower part of the tensioner. Once you get the sicket it, you will apply pressure counter-clockwise to releave the tension and you can slide the belt right off:







Once the belt is removed, we just need to remove the bracket that is holding the 3 hoses that meet at the "T" that mount to the frame. Using an 8mm wrench, remove the bolt and this will allow you to just push the hoses out of the way when you remove the upper/foward bolt from the alternator. Otherwise, that hose will block you from removing the bolt all the way out.






NOW we can now finally work on the alternator. For me, before I unbolted the alternator, I loosen the bolt on the back of the alt holding the main wire. Useing a 13mm wrench, just loosen it for now and you can remove it as well as the plug on the back once the alternator is unbloted.

To get to the upper bolts it is very easy using 2 6" extensions and the universal joint with a E12 socket. I lossen the almost all the way out, but left them screwed in just a little to hold the alternator in place when I remove the lower bolts.





Next you can remove the lower alterrnator bolts either from underneath the car or from above. You can either use the set-up I described at the beginning of the write up, or you can see if you find a better set-up for yourself. Once the lower bolts are out, you can fully remove the upper bolts and the alternator will be lose. Now you can get to the plug and wire connecting to the back of the alternator and remove them easily now.

The is a bracket that hold the power steering hose in place and is bolt on with the foward upper and lower bolts. Once the bolts are all out, you can just swing it to the side to get it out of the way to remove the alternator.

Now you just slide the alternator foward and pull it directly out:





Now you can replace the alternator. Do everthing in reverse and just replace everything you've unbolted and you should be good.

Again, This should be everything, but if I forgot a step or are unclear, please feel free to leave some feed back. I hope this might help some of you!

 

Well done! I have to do this job next week to replace my voltage reg. I started to do this about 2 months ago but ran out of time and had to put it back together. It is really fiddly and not a lot of room to work. The bolts that hold the silencer to the block is a pain in the A** to undo and reconnect

I was actually going to document it and post as a DIY but you beat me to the punch.

How long did it take you to re&re?

Nice to see that I am not the only one that has oil in the silencer (I was worried when I saw it the first time I disconnected it

I found that a T55 also works to release the belt tension as I could not find anywhere a T60.
A wobble extension set is handy especially for the silencer bolts as well as a 1 1/2" extension as I found the 3 " too long

 

Thanks! Well R&R was about 45 minutes. Pretty quick, but this is my 3rd R&R. My second was about as fast. My first I spent a few hours because there were things I removed that wern't nessesary.

You don't even need to remove the upper hose! If you find a better way, or something to add to this, please fell free to take any pics/info from this diy to make a more complete one.

BTW, what's up with that oil? You think it's a real bad thing?

 

My comments since I just did this repair to change the VR which I got for $59 which is miles cheaper than what MB charges

1. the bottom front alt bolt is a real pain to get at and the only way around it is that I used the box end of my 10mm spanner to remove the bolt as there was no way I could fit my star socket and drive in any direction due to the very stiff power steering hose. I had to do this from under the car

2. I would recommend undoing the small bolt that holds the PS hose to a bracket to make access easier and to get the alternator out

3. Be prepared to have an SRS error code when you reconnect everything. A trip to the dealer or specialized indy is the only way to clear it.

4. taking the undertray off helps with accessibility and retrieving the odd tool that you drop. I took off 5 of the 6 bolts and it does not take much time to remove

5. Make a note of the direction of the belt and the way it goes around all the pulleys as it can be confusing to remember the exact route, it really is a nightmare of all the turns and bends

Not technically a difficult job, it takes time because of poor accessibility and tight quarters. It is really fiddly and you will curse at the ridiculous tightness (lack of space) to get at the bolts. The wide band silencer is a PIA to remove and to install because the bolts are offset and in a blind area

 

Great job leeer for putting DIY together, ur descriptive diy had really helped me change VR. Abt the bottom ALT bolts, i found it much easier to stand on the passeneger side of the car and work from the cavity between the battery and coolant tank. there is enough space there to get your hands and tools in from the side and then extend your arm all the way in. Infact those bolts were relatively easier for me to take out.

Everytime I hear $60 bucks for the VR, it really hurts....i paid over $200 to the stealership

 

Don't fret to much about the extra $140 you paid at the stealership because it cost me $80 to clear my SRS message after I hooked up the battery and alternator as it threw that error message and the only way around that was to go to an indy with a star diagnostic equipment. MB toronto wanted $138 to clear it.

You did not have any error messages when you hooked everything back up??

I tried to get at the bottom Alt bolts from where you said and while the lower back was ok, I could not budge easily around that PS hose as it did not give me enough room to get at the front lower bolt. Rubber hose was very stiff because the metal pipe it was attached to was in the clear path of that bolt

 

My battery was unhooked for a few days, and there were no error messages to clear. I got at the lower bolts by removing the wheel arch liner on the passenger side. Clear shot from there.

 

>> So You will need a T80 to do this, you will find the "hole" for the

Hey, I'm following this. You got a typo with the T80, should be T60. The 13mm

>> Useing a 13mm wrench, just loosen it for now and
This is unclear. But I did use a 13 mm to remove a wire from the alternator.


heeeeelp.
I'm stuck. I was wondering if you can help. I have no idea how to put the timing belt back on. It's hard. Using the t-60 and pushing it down, my friend tries to snap that back in but the tension is hell. How did you do it? I'm currently using a 3/4 wrench /w t-60, the middle size, this is my first major car repair diy. Knows nothing about tools.

oh I broke the zig zag wire that connect the coolant to the engine, it was in the way when I try to unscrew the alternator with the E12(?). I think I can hose clamp it back. Rescrewing the alternator I find that using a 13mm ( if i recall corrrect) wrench is a lot easier.

Thank you for this post. Hoping you reply soon ^____^, have work on monday.

edit:

did you use your bare hand to try to get the tension belt back on? like right hand pushing down on ratchet t60 and the left hand to pull the belt back on? Or is there another tool for that... T_T

 

Are you using a 3/8th " drive or a 3/4? 3/4 is pretty huge and should give plenty of leverage to turn the tensioner. I used a 1/2" drive with no problem. Make sure you are pushing down on it in the counrt-clockwise position, make sure the belt is snaked correctly through the pullies and make sure the belt is sitting correctly in the grooves of the pully and pulled as snug as possible.

I'm pretty sure that I was pushing down with my left hand and used my right hand for the belt.

 

put the belt on tensioner first and all the other pulleys that have grooves. Then using your ratchet and T60 push down on the tensioner and slip the belt over the large dark grey pulley (it has 4 torx bolts on it, rounded edges and smooth and is to the right and above the alt).

the zig zag 'wire' is a thin metal pipe that connects to the engine with a brittle plastic insert, check my posting under M271 engine maintenance item https://mbworld.org/forums/c-class-w...ance-item.html

 

I got it thank you.

I was like wtf, you guys gotta be super strong for the tension. It turns out, I put the t60 wrench above the belt so when I turn CCW, it was putting tension onto the belt with the wrench pressing on the belt. >______<

The thing I broke I gotta replace now... damn. Do you guys know what it is on top of your head? I got pictures... hehe. But regardless of this, I would like to say thank you very much for the diy and your tips. Thank you to Leeer73 and Boom vang.

edit:

OOOOOOOOOOOOOH, just re-read Boom Vang post. THANK YOU omg, I'll read it now for the zig zag.

 

How can you replace just the pulley on the alternator? I got a brand new one last year, want to see perhaps if it's just the pulley itself.

 

Bosch Alternator is really a good replacement. I tried installing a new alternator. Disconnecting the wires would be quite difficult and reinstalling it and replacing could be costly because of labor costs. I get to have a problem on the serpentine automatic belt tensioner so I've got to also replace it.

 

Nice write-up leeer73. I will add this to the wiki when I get a chance.

 

When putting bolts into the aluminium engine block you might want to check the torque settings. I realise it works in the short term but you would be shocked how many strange torque settings there are on the engine.

For example the water pump is like 18Nm in some cases. You can never tell the torque settings just by removing the bolt as it may be harder to remove than its actual torque setting.

I hope you did the belt and tensioner at the same time. It often turns out that the belt is ruined when major parts wear out.

 

Nicely done Leeer73. The only thing I would change is to remove the negative battery cable first.

 

Thanks for the DYI. I R&R my alternator yesterday, the $$$ light came on and said go to the shop. I replaced the battery and then had the alternator checked at one of the automotive box stores (they do it for free),Bad alternator. Just want to add something, I was able to get to the two bottom alternator bolts by removing the passenger tire and half of the skirt (the front part) and the two lower bolts where no problem. Thanks for the info on your DYI. Just a note: When I hooked my battery back up, I had no problems (Thank God) everything worked good. 2005 C230 Sport

 

Guys, how the *eck did you manage to remove the 13mm nut on the back of alternator? It seems like it's soldered there. I was thinking about removing the motor mount shield and using a breaker bar on it or something. Any ideas?

 

The bolt on the back of the alternator was tough to get off, so I used a breaker bar, you can also use a long pipe if you need more leverage.

 

Ok, I got 'er done today. Thanks for the DIY!

Took me almost 3 hours. Of course the pulley on the old one has seized. So their lifetime is about 7-9 years I guess.
Removing the silencer is ridiculously easy compared to the lower front alternator bolt. Frikken PS hose is in the way big time.
I had Bosch alt. in my 2004.5 - there has been debates as to which cars have Valeo vs. Bosch.
You can tell which one is in the car by observing the number/pattern of cooling holes on the front of the unit and comparing to pictures.

 

Lost eng power after I changed out the battery. I changed out the battery and the alternator,everything went fine, but now the car does not seem quick anymore, like it’s dragging.2005 230 sport Kompressor. Thank you

 

GREAT thread! This was a great writeup and good pics to get me through the painstaking process. Which was more the tight area to work in. SAVED Tons doing it myself. Thanks again!!

 

Hello someone please help me i have a feeling i really messed up on this alternator replacement project... I followed leer instructions for the alternator and everything went good..i bought a remanufactured valeo alt from napa autoparts. everything looked good put everything back and turned on the car and all buttons and lights were working, radio was working and was excited and as soon as i turned the key to start the car, all i heard was a spark noise like and everything just went dead... now nothing is working pls pls help...this is my work car..and i am stuck...my first diy and i feel like i made a big mistake trying to do it myself...

 

Check connections on alternator and check voltage at battery. Did you ever get the car turned on or did it die before then?

 

Just replaced mine this weekend as well. Alternator I purchased had a tag on it stating to make sure the battery was new or had a full charge. Put a trickle charge on it and no problems here. As said above do check that you have the cable plugged in properly and the cable that screws on seated well.