So, I have this old 2013 E550 which has multiple issue. It's on the end of life cycle so I don't give it as much care as it should to be perfectly honest.

Alternator started giving issues with randomly stopping charging, getting me stranded while getting back from work, only to charge battery fine after next start-up (and a battery charge). I was removing undercover to see how I'd remove this guy from the tiny work space and saw there was oil leaking from the cover plates. Opened the hood and saw plenty of oil and dirt deposit on the motor. Saw some place where it was more liquid, indicating it was closer to the leak. Removed the driver side turbo intake and saw this small kind of cap behind the belt. Seems like there's a small pool of dirty oil there. I have no idea what's this part is (only a DIY working on it when absolutely needed and having to follow tutorials found online). I also realized the turbo intercooler is leaking, again. Oil and dirt spread everywhere and the alternator is a mess. With some luck a simply cleanup will fix it, but I still have to figure out how to take it otu with the least amount of work.

Since the car has been knocking for almost 85k miles (now at 340k KM or about 211k miles), has main electrical harness issue, transmission slipping somewhat under hard acceleration, fan for heating/climate control randomly not working for 2-5 minutes about once per months before starting like magic happened, I simply want to get a few more months before I need to remove it from the road. Having had too many issues IRL job/covid/etc to be able to afford another even if looking at used market, so it's hard to say goodbye to a car so comfortable to drive. I know next one will not be anywhere near this E550.

So, anyone is able to tell me if this kind of cap could be the oil leak culprit and if so, how is it called? Simply need to unscrew it after removing the belt?

Also, if someone knows if I absolutely need to remove the radiator to get the alternator out, I'd liek to know as well. Trying to avoid this due to working outside in the cold (-5 to -20 celcius).

 

Did you ever had your timing chain tensioners check?

 

2 MB dealer refused to even take a look at the motor, telling me the only option was to have it removed from the car and sent by train to factory for a full rebuild. Considering the current value of the car and the cost associated to this, it's a no go. Driving it until failure. Never expected the motor to outlast other parts to be honest

Still, if anyone knows the steps to remove the alternator on the 2013 e550... feel free to let me know!

 

Wow, 200,000 miles. You are my hero. Folks will be along with WIS info for you to change out that Alt

 

That would be helpful!

 

So, have to fix the alternator so I went in and drained coolant, removed fan and am close to being able to remove the alternator now.

Looking at it, I can't see anything wrong. It's clearly brand new, shows no sign of wear and tear and didn't see any dust from road nor oil leak!
🤣

 

Looks can be deceiving: ALT may well look good but have wornout brushes or rings on the inside.

Replacing it @200kMi is a pretty good idea with serpentine kit now you're in there.

If voltage control remains an issue, consider this simple shortcut by unplugging ALT control plug.

This will bypass ECU issues to easily supply a perfectly good self-regulated 14v output.
Nice and easy, no troubleshooting not'in... done!

 

Well the no wear and clean was a joke. If you look at the picture, you'll see there's almost 1/4 inch of dirt mixed with oil stuck everywhere on the alternator.

I've removed the 2 front bolt (see new picture) but it won't move. I've tried stucking my head in between the radiator and motor and searched for some other bolts but didn't see any other, nor from underneat. The view is pretty limited TBH. Anyone knows how many bolts are fixing the alternator to the motor body and where the others are (if more than 2).

 

mine was on with 2x long bolts through the side.

 

So there was 4 bolts total or only 2 on the side?

 

Managed to get it off. There was no other bolts, it was only stuck in place due to grime and deposits. Using a small prybar screwdriver, I could push on the alternator frame right beside the lower bolt if anyone ever has this issue. It started moving without excessive force and then wiggled it until it came free. I had to remove basically most pipes to get it out. The only one I didn't remove was the piping from turbo to the motor, and I still needed to removed the alternator from under the car. I don't think it is possible to remove it without a full coolant flush as the fan need to be removed just as most bottom piping for the coolant.

So after removing it, I cleaned a little bit as it was a huge mess. The voltage regulator contact point are clearly worn out as you can see in the picture.



Bearing and alternator are in great shape except for the contact point for the regulator, which are slightly grooved in. I'm still wondering if I reuse it or not. MB is asking 1300$ with 2 business day to deliver it, which is plain crazy considering the Valeo ( it is the OEM brand I removed from the car) sells for about 500$ in other online store. Downside is they are asking for 1 week delivery and it's my only car.


Since I had every coolant pipe removed, I decided to check further for 2 issues I knew. Heating had been having some issue with car not keeping temp at 85c during very cold temperature (-20/-35c) as well as the previous leak I saw. Removing the pipe going to thermostat, I saw the gasket is ripped, so coolant must have been circulating even when it shouldn't. Also, on the right, we can see the black cap from where oil seems to be leaking. Anyone knows the name/use of this cap? I was scared removing it without knowing what's it's for

 

if you decide to replace ALT brushset, I suggest you use only OEM regulator! The aftermarket china-compatibles use hard carbon that waste the soft copper rings ie. kill the alternator core.

Good call on your bypassed thermostat ring !

 

How safe is it to bypass the voltage regulator by unplugging it ?.

Edit: Nvm, don't think I'd risk this.

 

In your case, the brushes have done their time. No bypass can fix that.
Replace a new $40 Valeo regulator then check if you still see evidence of bad voltage regulation below 12.3VDC

"LIN Bypass" is not a "regulator bypass" per say, it's "ECU-LIN-ALT bypass". Disconnecting LIN remote control lets the regulator work independently to deliver a stable output regardless of faulty ECU commands.

 

Well actually I had some issues the last 4-5 times I drove it. Getting back from work, I had a battery red warning while in highway. As I was pulling over to the next exit, central dash+command closed itself. Drove another 500m to remove myself from traffic, stopped the car and checked battery voltage with my multimeter which I happened to have with the toolbox I was bring back home. All seemed fine, so I started back the car and drove another 50km before the red warning came back. Stopped again, checked if there was a way to verify charging and enabled the hidden menu trick I saw to show voltage and charging rate in amp.

Started car again and charge rate was at 80amp with voltage at about 14.5v so I thought it was another random electric issue maybe with the harness. Next day I had a 3km drive to make to get something. After 300m red light came back. Stopped at the grocery, got sheet I needed and started back the car with secret menu. Charging was still fine, just as voltage. That reassured me it could be only a stupid bug like when my AC/heating fan bugs for 2-3 minutes for no reason at start up. Later that day, another errand and the alternator was still charging even with the red warning light.

Since I had a very important appointment next day, I couldn't do much work on the car and was reassured seeing it charge each time I checked it. Took my E550 again, only to have the red warning light after 5 minutes. I decided to ignore it, but that time, it didn't start to charge. After 30 minutes, central control closed so I stopped. I was close to a car part store, so I headed this way. All system started shutting down one after another. Abs, stability control. Volt were down to 10.2 so I stopped the car completely to avoid busting transmission or ECU.

Tried to call towing but with a freezing rain and the accidents, none were available before multiple hours. It was also as expensive to get a towing than to purchase new battery, so I walked to the car part shop and got a new battery so I could limp home. Switched the battery and drove back. 30km later, with battery down to almost 11.2v, I was getting worried I would not make it. Hit a pothole and all of a sudden, it was charging again.

Having now looked at the worn brushes, pretty sure it is the issue and that some shaking was enough to have a temporary contact.
​​​​

 

Good job tracking things down with the secret menu and swapping a new battery to get home without tow-truck.

Once your alternator is working again, use the "secret/workshop menu" to keep an eye on charging Amps. it will help you see what the ECU LIN is commanding.

 

Did anyone find out what was the plastic / rubber cap on the right side of the engine??

 

ALT LIN unplugged 👍

I have just joined the ALT Freedom group
I want to see how this help REBOOT stability last longer.

W212 M276.059 responds noticably well to stable conditions and poorly to managed chaos.

I think MB is using the smart voltage control 12.6v to 14.9V to further help SCREW UP CAN data coms.... I am going to experiment this for a while as on my way to sanitize the unstable factory CAN wiring looped through F-SAM (resistors).