I picked up the 18" flexible ratchet at HF and it is pretty handy. Its about as thick as my 1/4" extension so it fits in the engine bay easier. Using it I am able to reach the bottom front nut and the 3 top nuts without even removing the air filter box. Tried to see if the nuts would come off easy and no, but i didnt put too much force on it yet. Seems 3/8" drive sockets are a little too big to fit so im using all 1/4" sockets. I only have a 10mm regular socket and deep socket so i ordered a 1/4" drive 10mm set that has a swivel socket, mid-length socket and magnetic socket.

 

You're killing it Tim, great job and your documentation and photos are deeply appreciated both by me and those who find this thread in the future.

I've been working on other services but am going to read through this thread in detail when I get to this.

Funny how clever your nozzle + boroscope trick is; I was thinking of doing the Exact same thing except 3D printing a jig for a mirror on a wand that also holds the straw. Your idea is way better hahahaha!!

Amazing that you are able to get to the bolts like that! I have an M273 in my W212 (2011 E550) and wonder how the layout is different. Mine seem extremely difficult to get to.

The nuts conundrum is very interesting. I noticed the exact same details. EPC has both listed for the M273 for my year make model; no noticeable difference in the nuts but definitely in availability and price. I see now that you have the V6 so the difference in access makes sense.

 

I just want to make sure that this is a job I can actually do in the driveway. Figure if I go thru the motions on what I need to do to verify I can do it and so there are no surprises after I started the job. Once I start I have to finish it, I cant be stopping to order a tool or order something. Thankfully the exhaust leak isnt that bad so I can take my time getting things figured out.

I like taking photos so I can view them up close on the computer and really see what im dealing with.

In trying to search for the "best" rust penetrating fluid I keep seeing people claim that heat is the best. The is no way i can fit a big torch in there but remembered I have a small butane torch I got for soldering wires together. I have to get some more butane to try it out but I went in the engine bay and I can reach the nuts with it. I think this will be good to have on hand.






Right now i'm searching for a good 10mm wrench. I was playing around with the new manifold and realized I cannot fit my 1/4" ratchet on the two bottom middle nuts, the ratchet hits the manifold. And thats with a shallow socket. It fits when I put my swivel extension on but it seems like a sharp angle I prefer not doing. I did order a 10mm six point swivel socket that may work better. But I tried my small 12 point 10mm wrench it it looks like thats a better way, but I want to get a 6 point wrench if i can.

This is where the ratchet ends up if i have the socket straight up and down. Wont fit over where the nut is.



If I tilt the ratchet to fit then the socket isnt on flush.



Wrench will fit fine.



Swivel adapter works, but I dont like the angle. Plus I think the engine mount will be in the way at this specific nut for this to even work.




I'm getting better using the borescope. I turned the camera on then I taped the straw extension so its at the bottom, makes it easier to find the orientation. One thing I noticed with the Liquid Wrench is it seems to evaporate over time and i couldnt see any left on the studs earlier today. I sprayed PB Blaster just now so i'll see how that looks tomorrow. I'm going to start wire brushing the studs to clean them up, should have been doing that from the start.












Heres the top of the header bolt, the bolt on the inside that I cant even see without the borescope. Does a good job of being able to hit it with penetrating fluid. The picture on the borescope screen is much better than this photo shows. I took the photo using my phone.

 

That butane torch is great. Used that exact model for many years as a teenager.

Have you considered a ratcheting wrench that has a pivot? Maybe one of those wrenches that has an S shape to its body?

I hear you regarding either fully committing or not. Maybe whether you can get each nut to break loose or not could be how you decide which path to go.

Have you seen this comment? Maybe a new penetrating fluid you've considered: https://mbworld.org/forums/e-class-w...ml#post8579663

 

SUCCESS!!! Started getting the nuts/studs loose.

The 18" flexible ratchet contraption really is handy. Received the 1/4" 10mm socket assortment set so was trying them out to see how they fit. It has a 10mm swivel socket that has a hole in the socket part that allows the stud to pass thru, though I may open it up a little more with a drill bit.

I had the ratchet on, plenty of penetrating spray, and kept trying to loosen-tighten-loosen-tighten then finally the nuts started loosening. The didnt break free, instead they just started slowly moving. I wasnt using too much pressure. The ratchet itself has quite a bit of flex. I feel so good right now that they are coming out. I couldnt tell if the nuts were coming off the studs or if the studs were coming out. I tightened them back up since i still want to drive the car and dont want the exhaust leak getting worse due to loose nuts.

I'm thinking the bottom nut closest to the engine mount will be hard to reach with sockets so I ordered a 10mm offset wrench that should fit anywhere. If I dont end up using it ill just return it.

The 5-piece set was only $7.97 on Amazon but I guess I bought the last one. They have the same set just under a different brand for $11.67. I like the swivel socket because it is much shorter than using my swivel adapter on a 10mm socket.

 

Posting some more photos so you can see what I mean about needing all different lengths of sockets and extensions. The long ratchet i'm using is 3/8" drive so I need to use a 1/4" adapter. In my opinion 3/8" sockets and extensions wont fit, the manifold itself is in the way. For the top front nut i can use the intermediate 1/4" 10mm socket with the ratchet just fine, but for the top middle nut the ratchet ends up hitting the manifold. The manifold is fatter at that area, so I ended up using the deep socket and the ratchet just barely clears the manifold. I would like a slightly longer socket or a really short 1/4" extension. maybe i'll see what I can find.

And for the top rear nut i have to remove the air box to be able to reach down and guide the socket on. Plus the sockets tend to get stuck on the nuts so I have to be able to reach down and yank them off.

I've had some luck using tooth-brush type wire brushes to hit the threads and clean them up some.

Top Front Nut:







Top Middle Nut: Can see the head of the ratchet just clears the top of the manifold using the deep socket.

 

The extra-long ratchet has two joints in it to move. Then I have the 10mm swivel socket plus a set of swivel adapters if needed. I'm trying to squirrel together every single tool i'll think I may need.

Realized I will need a way to remove stuck/broken studs. I have a set of vise grips that should work though I just ordered two stud extractors. I think the studs are around 6mm, my order from FCP should be delivered today so I will know better when they get here so i can try everything out. I ordered a 1/4" drive extractor and a 3/8" drive extractor. The 1/4" says it goes up to 6mm, and the 3/8" says it does 6mm-12mm. Some of the reviews for the 3/8" says it wont fit 6mm studs, so who knows. Better to have both on hand.

Going to work on the nuts some more later today, see if I can get the rest loosened. I think between the PB-Blaster and the Liquid Wrench those are dealing with the rust pretty good, just have to keep wire brushing everything to knock the rust off so they can penetrate the threads better. I think the loosening-tightening action is helping.

 

Wonder what size the O2 sensor is? I have to remove that section of exhaust pipe and disconnect the O2 sensor. I found I have a set of O2 sockets, They all say 22mm. Are they just different shapes depending on how its installed in there? Never removed one before.

 

After wrestling with the borescope cable trying to bend and twist it certain ways to lower down and hit the bottom middle nuts with penetrating fluid I realized I can just easily stick it thru from the front, its a straight shot over the engine mount. I also noticed the penetrating fluid I'm spraying on the top bolts is flowing down soaking these nuts so hopefully its had a chance to be doing its thing since I started.





Also wondering if there is enough space to remove the manifold once unbolted, probably wiggle it out to the left of the alternator.

Still thinking about the nut at the engine mount. I looked around for what the engine mount looks like and seems there is a notch in it on the left, probably have enough room to fit an offset wrench and get it off that way. I'd love to hear how anyone else removed it. I think that nut is where I put the red dot in the photo of the mount below.







Received the parts from FCP and looks like I ordered the correct parts. Looking at the studs and how small they are im glad I ordered the smaller stud remover. Also got a new smooth idler pulley, the one in the car sounds very loud when using my stethoscope on it. Wonder if it will make a difference.

 

I replaced the lower smooth pulley and oddly enough it sounds the same thru my stethoscope. The ribbed pulley is very quiet, but the smooth pulley is just loud. The old pulley seems perfectly fine, spins smooth and im thinking it is still good to go. Oh well, now I wont have to worry about it hopefully ever again plus it was on sale at FCP. Its the same pulley that was in the car. The box doesnt have the Mercedes part# on it anywhere so I scanned the QR code and it showed as an original product. I was going to get the pulley off eBay but was paranoid it may not be a real INA pulley.

I've had that pulley off a few times before and I still forgot about the small washer on the back side and almost didnt even see it. Took some photos even though its a pretty simple job. I still have the small pin that came with the belt tensioner so just used that to hold it open, tension off the belt. 17mm socket and small extension on a breaker bar to move the tensioner. E14 socket to loosen the pulley bolt then remove it by hand while holding the belt so it doesnt move. Dont have to remove the belt at all. Install new pulley and remember to install the washer, torque the bolt to 25nm/18.5 ft lbs.

 

Received the 1/4" drive stud extractor and it wont work, in order to fit the 6mm stud you have to back the jaws in so they are way inside the tool. So basically if the stud breaks and there is 1/4" sticking out the tool wont be able to grab on to it. Its a nice tool and seems to work fine, just not for what I want it for. The larger 3/8" drive should be here tomorrow.

I drilled out the 10mm swivel socket so now the stud can pass thru it. Worked my way up to a 1/4 drill bit and fits fine now.

I'm going to start a new thread when I start the work to show what I did. I'll try not to ramble on and on as much.

 

Well I did it now, snapped a stud. I was in there with a wire brush trying to clean off the rust then put a socket on the top front nut and it got it moving, this is the one closest to the exhaust leak so I went to tighten it back up a little and snap. I didnt even use that much force, though that ratchet is very long so probably used more than I thought. It did seem to be moving nicely, probably 1/4 of a turn before i stopped then tightened it back.

I started the car up and the exhaust leak isnt really any worse.

Not sure what to to do now. Bring it to Mercedes and have them fix it? Or keep going and deal with things as they come? this was my nightmare. Im looking at the break and it appears the stud snapped out past the manifold flange so there should be 1/8-1/4' left sticking out once the manifold is removed.

 

Tim you've done a world-class job so far. Extremely impressed with your work, research, problem solving skills, etc.
My plan, if I were to attempt this myself (extremely unlikely after seeing your journey), would have been to take it to a German mechanic (one that specializes in Mercedes/BMW) and have them take the reigns.
If you take it to Mercedes they're going to find an issue with your suspension and try charging you a kidney. I don't trust the dealerships but that's me.
Are there any independent Euro mechanics around you? Maybe an exhaust shop?
Seems it's drivable so you wouldn't even need to tow it.
You've already done 80% of the most difficult part of the job.

I wish you were my neighbor. I'd gladly give you a hand and bring a 6-pack.

Watching you do this I realize I'm almost definitely right about the "working space" in my V8 engine bay being dramatically more tight. I don't think this is a feasible job for me and wouldn't have been able to decide that without watching your incredibly well-documented journey.

You have probably the same drive, problem solving acumen, and resourcefulness that I do, but with a slightly less difficult scenario due to the difference in engine.
Time for me to start saving up for a shop visit. First one in so many years.

 

I dont think i'll give up just yet. I'm looking at the broken stud and I think I can get it out. I really think it was coming out but by tightening it back I think it fractured it, I think i turned it past the spot it was originally torqued down to. I should have just kept loosening it. I paired it to a new stud and there should be 1/4" sticking out from the head, I think my vise grips can grab it good enough. I really didnt expect all the studs to come out along with the nuts so I figured I would need a way to remove the studs which is why I ordered the stud extractors. By the way the 1/4" drive one seems too small and the 3/8" one seems too large, I dont see any way either will grab onto a broken 6mm stud with only 1/4" showing.

I have a set of old Sears vise grips to try. I wanted to see how easy the nut turns off the broken piece of stud and it turned fairly easily using vise grips and 10mm wrench.

 

Got the car up on ramps and going to see how far I can get doing this job.

Surprisingly the the header bolts are easy to reach, I remember one person writing in saying he couldnt seem to get the inside bolt so I was afraid of that one, but they are right there and can get them with an extension. 13mm socket. I sprayed everything down again with some Liquid Wrench just for fun. Wondering how i'm going to get that exhaust out of there, there is a cross member in the way so it wont just pull straight down, may have to get creative especially with the car on ramps.








I see there are two O2 sensors in the section so instead of trying to remove them which I cant reach anyways I traced the wires and the plugs are up near the maf sensor. In the photos can see the oil separator breather hose that goes to the throttle body. Just have to remember ones green and one is black. Its why i'm taking alot of photos. Can look thru this thread when i'm putting things back.






I saw the broken stud close-up and to me it appears there should be a decent amount of it sticking out of the head to grab on to. I ordered some reverse thread nuts for 6mm bolts, wonder if i can put that on the stud and remove it that way?

 

Shouldnt have said the header bolts are easy, i'm still trying to get them loose. I thought they were 13mm heads and come to find out they are 1/2" so I did a good job rounding one off, the second is getting close too. I ordered a set of easy outs, hopefully they can grab onto the heads. The bolts are in an awkward position where a swivel adapter is needed for the socket to even fit flush. The exposed threads look covered in rust and doesnt even look like a bolt. I got out my Bernzomatic little torch and tried toheat one of the nuts and still wouldnt move, maybe I need to hold it on longer to get hotter?

Other than that one manifold nut I haven't really broken anything yet so the car is still driveable. Try again tomorrow and see if i can get any progress done.

 

Received the set of stripped nut removers to try and get the two header bolts out. Put a flash light down there to see if the penetrating fluid i've been spraying on them is doing anything and it doesnt appear so. The exposed threads of the bolts are just covered in what looks like hard rust, I used some stiff wire brushes and it wasnt even making a dent in the rust. I just had the idea to try and chip the rust off, have to find something long and sharp to stick down there and wack with a hammer, see if that does anything. I tried spraying penetrating oil then driving around to get everything hot, also drove around then sprayed everything while it was still hot. Dont think the penetrating fluid is doing much.

Looking at the piece of broken stud/nut I dont see any of the nuts coming off from the studs, its either the studs come out with the nuts or the studs break.






Heres the new parts. The new bolts screw in easily by hand up until the very end of the nut, then it gets tight.

 

Just had a horrible experience. I decided to stop by a local auto repair shop to see if they can replace the exhaust manifold. I was told yes, may take 5-6 hours. The next day I get a call with them saying due to the 4matic they will have to pull the engine, it will be around $1,800-$2,000 and should hopefully be done friday. I tell them go ahead and just get it done. Friday comes and I call them to see if its done, they tell me they had to order the tool to remove the engine mounts off Amazon and it will be in Saturday. So I start stressing out thinking I made a huge mistake letting this shop work on my Mercedes. Thankfully they call me earlier saying they cant do it, something about them trying to start removing the manifold nuts and seeming like they will all break and have to be drilled out. He recommended i take it to an engine shop that deals with that kind of work.

I pick up the car and the check engine light it on. The passenger side engine mount shield along with the front drive shaft shield are in a box in my trunk. I get home and im now going thru the entire car. They removed the exhaust it appears and put a basic clamp back on, no big deal ill order a new clamp. The twi wires for the O2 sensors are all tangled and not secured, one was very close to rubbing the drive shaft. One of the air box metal clamps is missing, not sure how that happens since i cant even budge the other ones.

i was able to clear the codes expect for one, having to due with the abs. Hopefully its just from low battery or it being disconnected. Im charging the battery right now. I'm also ordering a new air box clamp and exhaust clamp. Im going to order an engine mount wrench to double check the mounts are tight.

Looks like they were able to get the two rusted header bolts out, but now there are nuts and bolts in there, instead of the affixed nuts that belong on the exhaust manifold. i have no idea how they even got the nuts on. Im trying to fish my hands down to re-secure the O2 sensor wires out of the way.

I am so happy they didnt end up pulling the engine and only seemed to screw up a few things. The exhaust seems louder now a bit since the header bolts dont appear on tight, that joint must be open. But thankfully also i looked and they didnt break off any more manifold nuts/studs.

Think i'll take it in to Mercedes and see what they say, i'm curious if they say the engine has to be pulled. or would removing the head be easier/less work? i dont know.

 

I had 3 check engine codes. The first set I was able to erase but the 5001 code wouldnt let me for some reason. I have the car up on ramps at the moment so will try driving around tomorrow to see what happens. The 0365 I have seen before and may be related to when the red battery warning pops up if i havent driven the car in a few days. The 0443 may be from the shop messing around with the O2 sensors, I can tell they removed that section of exhaust seeing as they failed to properly secure the wires back where they belong. Not surprised if the wire was rubbing the front drive shaft on the way home. Using the scanner i remember it mentioning something about the front SAM and i've read the 0443 may be related to fuse #19 being blown? I'll have to check that too.

I am blown away at how that shop left my car. When I picked it up i noticed the cover for the radio was open which I know for a fact was closed when I dropped it off, I never have that open so I think that is very strange. Not only did they not put the heat shields for the engine mount and front diff i cant find the bolts for them anywhere.

Now im just ranting. Thinking how i'll have to go thru the car over again tomorrow to see if I missed anything they screwed up. No way would I ever go back to them, not even going to bother asking for the missing bolts and air box clamp i'd rather just get new ones.

One EXTREMELY positive thing is they didnt end up pulling the engine, it would probably never run right again if they had. I still question if the engine has to be pulled to do the job. And if it does have to be pulled I might as well have the drivers side manifold and gasket replaced since im thinking the nuts attached to that manifold will get mangled. I'll have to call Mercedes and see what they say.

 

Good thing i do take tons of photos and save them. I was going through previous photos and back on Aug 5 2023 when i first got the Foxwell scanner I had two of the same codes, so hopefully its not an issue moving forward. Just have to figure out the 0443 issue.

 

Just made an appointment for this Friday to take it to a shop listed as working on Mercedes and BMW. Its hard getting answers out of people on the phone since they all seem in a rush and just say "drop it off". I asked if pulling the engine makes sense to replace the exhaust manifold on a C300 4matic and he laughed saying "No".

When I was under the car previously I noticed a metal brace going over across the middle section of the exhaust and remember thinking it will have to be removed to drop that section of exhaust pipe, except the bar ran underneath the two side plastic undertrays. Was just under there and saw what that shop did, they just cut out the undertray in pieces to remove the bar. I am completely outraged at the hack job that place did. I also think they put the two O2 sensors back in the wrong places, switched them.






The metal shields for the front diff and engine mount they didnt put back or include the bolts to install them:

 

I just checked by unhooking the O2 sensors at the harness and it does appear the O2 sensors are switched, the forward is where the rear should be. The bottom O2 sensor is fairly easy to get to, but the top one doesnt seem possible. From below no way to possibly get my hand up there to even fit the socket on. I was able to fit one of my o2 sockets from up top but wondering how to get the ratchet on.

Odd that would cause only one code, I would think both O2 sensors would throw codes if they were switched? The one installed at the bottom (which should be #1 at the top) appears to be bent near the wire, wonder if its just broken now?

 

I went ahead and ordered a new upstream O2 sensor from FCP next day delivery so it should be here tomorrow in time for me to bring it to the repair shop. When I unhooked the sensors to see the part #'s sure enough the upstream sensor is installed at the bottom. That sensor has a 2016 date on it so it was replaced at some point in the past, wonder if they had to drop that section of exhaust to do it? I can get my o2 sensor socket on it but I cant seem to attach a ratchet though I got frustrated and gave up for the day yesterday. I'll wait to see if I need a new downstream O2 sensor since that one I can do myself since its easily reachable.










I'm taking it to Import Autowerks which says it deals with Mercedes and BMW and im seeing all positive reviews. I'm really hopeing they can figure it out and get the job done. We shall see I guess. If they do get it done i'll try and ask them what they specifically did so I can let everyone know.

I tried to figure out how that last shop got the two header bolts out and I think they maybe cut them out somehow. The nuts that are attached to the exhaust manifold dont look like they are there anymore and instead just a regular nut and bolt is there, very odd.

Now i'm stuck trying to track down new undertrays for the sides that the shop cut away. New they are around $160 each, finding some used for around $100 each. Maybe I should try local salvage yards since its the shipping costs that make them cost so much. I double checked and sure enough some of the bolts werent even tightened all the way. Im seriously going over the entire car checking EVERYTHING. The wrote an R with an arrow on one of the braces they clearly removed, its on the passenger side so the right side but the arrow is pointing to the rear of the car?













I was searching for all the bolts to re-install the two metal shields and they appear to all be M6 bolts just all different lengths. I ordered a bunch of M6x12 bolts (910143006000) since FCP had them available. If the bolt ends up being too long I figure just add a washer and call it a day. Or even get bolts from the hardware store, I usually only like using Mercedes hardware but for these shields I dont think it really matters as long as they are back on. In the parts diagram for the engine mounts they show a picture of a different engine but the part #'s seem to be correct for what I have.

 

Received the new upstream O2 sensor and it appears i was reading the date wrong and the one in the car is most likely the original manufactured in 09. The first set of numbers is the year, it appears. Noticed there appears to be anti-seize already installed on the threads, I never held a new o2 sensor before.

Got the new airbox clip which i really couldnt wait to get, the air box felt loose with that one missing and it wasnt seating well over the maf, wasnt lining up and i had to reach down and force it on.

My appointment is tomorrow so hopefully I can get some answers if they can install the exhaust manifold. Fingers crossed.

 

Good thing I went ahead and ordered a new exhaust pipe seal ring, looks like the one in there is crushed and falling apart. They are probably one time use anyways, they look like they are made out of metal mesh and must form a seal when the clamp is tightened. had to order a new clamp for the left side since they just put a regular U-type clamp in. Im pretty sure that clamp was all rusted so not the shops fault.

Trying one more time to remove the O2 sensor, I dont feel comfortable driving around knowing they are switched, im paranoid it may mess up the cat some how? Such a project just getting the car up so i can even fit under, and its just barely.

I took alot of photos of my car when working on it before, now after this mess im taking even more. Would be nice to have proof the plastic undertrays werent cut away prior to that shop getting ahold of it but dont think I have any photos specifically showing it. Should have taken a photo of the mileage too, soon as I started the car the low fuel light came on and I know I had 1/4 tank when dropping off, now its much lower. Did someone take it home and drive it around? The cover for the radio was open when I picked the car up and I never have it open. I had some money stuffed in the arm rest I keep there for emergency which I made sure to remove prior to dropping the car off thankfully.

Tried to fit the metal shield for the engine mount on but it wont fit, must have to be fitted from below when the exhaust pipe is removed. Received some M6 bolts that will hopefully work to re-install both metal shields.