So, I own a C400 and I really want to love this car (first Merc) however, I am growing further and further away from that thought every time I have to take it into the shop.
My previous car which I still have and drive is a 2004 Saab 9-3 Arc with a stage 2 tune. Have had the car for 9 years and put on 160k miles, only had to take it into the shop once for a broken coil spring...
This C400 has been a totally different story over the 2 years I have had it and the 25k miles I have put on.
Below you will find the issues and the fixes, I hope this can help others out. If you want the part numbers, let me know.

1) Squeaking noise coming from drivers side suspension going over bumps or when turning = Left front lower control arm worn, replace control arm and ball joint.
2) Hissing noise from brake pedal when releasing = Replace brake booster.
3) Service Campaign #2019080019 = Replace suspension bolts that prematurely rust.
4) Front passenger door speaker rattle/buzz at certain frequencies = Replace retaining clips for the speaker trim.
5) Car vibrates when put into reverse = Replaced both front motor mounts.
6) Front drivers side door sometimes not unlocking = Replaced door lock.
7) Ticking noise from the engine after driving in sport mode for ~15 mins = Tech found purge valve to be slightly louder that normal, adjusted valve, sound is now quieter however still may hear normal op noise - STILL TRYING TO SOLVE THIS.
8) Rear passenger side of car lower = Replaced right rear air spring.
9) Ticking noise from engine bay = Lubricate pivot point of front defrost flaps and linkages.
10) Rear right window switch on drivers door not working = Replaces window switch pack.
11) Fluid leak from front differential = Replace oring and screw.
12) Air suspension malfunction = Pressure relief valve and broken wires replaced.
13) Rough down shifts from 5th to 4th and 3rd to 2nd = Replaced transmission valve body.
14) Aux battery malfunction = $350 to replace battery.
15) Popping noise from front axle when turning = Replaced front left axle.
16) Door handle LED lights not working = Replaced multiple.
17) Vibration at 55MPH = Replaced wheel bearing.

I may have missed some others... side notes would be that the windshield is crap, every time a little rock hits it I end up with a 1/4 inch crack.
Also the wheels are garbage, two cracks so far and when I bought the car all 4 wheels were bent!
O and I have also gone through a bunch of felt tape and pieces of rubber trying to stop all the creaks and rattles in this thing too. My wife's Hyundai seems to be better build quality.

 

I’ve had some of these issues, some I’ve fixed, some will be fixed this upcoming spring. I did my research on the common issues so none of mine “surprised” me. I also got a good deal on mine. It’s a lot of car for $23k and is 80% of a C43 AMG which is twice as expensive. I’ve had my car 25k miles and haven’t had as many problems as you though...why not just sell it? And get a C450 or C43 if you like the car but don’t want as many issues?

 

Agreed, it is a lot of car for the money, I just didn't imagine this many issues with a Mercedes "the best or nothing", especially the creaks and rattles in the interior.
Thought about a C43 but concerned I would have the same luck. If I got another Merc it would probably be a E class, not an Alabama made c class. Also thought about getting an Audi but they look so bland...
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I think you spotted the issue when you mentioned Alabama made C class. Mine is Stuttgart, Germany made. I have it for 2 years and a half almost 75 k kms. I frankly was socked reading your list. My is as follows:
1- replace aux battery.
2- replace the oem battery which died after 5 years.
3- sun roof issue. Fixed once for all. To be honest i believe some small stones came into the rack. These stones broke something in the left the rack.
4- replace rear break pads. Normal wearing in 2 and a half years.

So basically i had 1 issue for a 2015 car. 75,000 kms. I looked into the car maintenance history at my local dealer, the previous owner has been doing Service A and service B. I didnt see that he fixed issues. We have one single dealer in Lebanon so why would he use outsiders when his car was under warranty. I like driving this luxury car. I had a BMW 330 xi its no where near my current machine. Indeed its the Best or nothing.

 

How did they diagnosed this? I have a problem at around that speed as well in my RHD C300.

BM

 

I just took it to the dealer and told them there was a vibration at 55mph. They drove it and confirmed that the vibration was from a bad wheel bearing.

 

ok so do you want us to throw our cars away? If your car came with 4 bent wheels and all those problems, then obviously somebody beat the everloving crap out of it.

but I guess we should all go buy 20 year old Saabs

 

I recommend you sell your Merc. Your list is shocking something was wrong in treating this car. Just get rid of it. My Merc. had one single issue in 5 years ie Auxiliary Battery. The car is a 2015 model. For me Mercedes remains The Best or Nothing.

 

4 bent wheels plus blown out suspension, broken axels and broken wheel bearing obviously the previous owner drove like a maniac.

 

Was #9 a DIY job?

 

This was done at the dealership. Didn't completely eliminate the issue but it did make the noise a bit softer.




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I guess the disappointing part for me was that the car was super clean, 26k miles, and had just gone through the CPO process when I bought it however all of these items were missed.

Since a couple of these issues took multiple trips to the dealership for them to figure out I wanted to make this post to possibly help others if they find they have a similar issue.
a few of the items on my list here have been on this forum with the solutions. It was great to take my car in and say other people had this issue on the forum and the solution was service bulletin xxx.xxxx or part number xyz to fix. So I thank the community for that.

 

Currently planning on selling. Still have some time to decide what to get next since the extended warranty is up on this one October of 2021.
Which model do you have?

 

man that sucks. I guess I'm lucky that my dealership here is just awesome. C400 is such a good car it really sucks yours was messed up.

 

Sure does :/ Glad you are having good luck with yours. Maybe I just got a very early production lemon.
Just pulled up to work today and came across a new issue for the first time. Car would not shift into reverse. Had to put it in park, then it wouldn't switch to drive or reverse. Turned the car off and back on and then shifting worked. Weird stuff with this machine.

 

I have an early production fully optioned C400 with 72,000 miles. Had the Aux Battery issue but other than that just routine maintenance. Seems like the previous owner really abused your car. I also don't understand how a MB CPO car would be sold with four bent wheels.

 

mine is early too, had my axles and sunroof updated thats all really except one o-ring

 

I recommend you use the fact that it has to get a better price for it and sell it fast. I currently own a C200 AMG line built in Stutgart, Germany. My plan is to upgrade to C43. I am just putting things on hold due to the current epidemy.

 

I respect the intention of your post and I understand your frustration. You were really unlucky with this car.

 

Yeah I was very frustrated and confused. I discovered this a couple days after I bought the car. They straightened the 4 wheels and replaced the tires. Every since that I have doubted the CPO process.

 

why? Sounds like they did about 6-7,000 dollars of warranty work on the car. MB lost their *** on it and I bet they wish they never sold it.

 

I have a very similar experience as the Op. I can't complain about the service through my extended CPO warranty. The car is in tip top shape at the moment and running well thank goodness! My C400 has had a lot of warranty work unfortunately. Replaced a noisy screen, touch pad failed, usb replaced, engine mounts failed, rear camera failed 2x, front differential was leaking, axels were clicking, and probably some other stuff I can't remember. It was disappointing to go through all that. Hopefully it is good now but who knows. The warranty is about to run out in December and I'm somewhat nervous. I paid the car off though so hopefully I can ride it out. I tend to keep cars a long time but I don't know about this one. The suspension is super stiff and my back might force my hand to get something more comfortable. Still. The engine is a gem!!!!!! Always gets my pulse racing!

 

I don't know about the noise screen, but apparently the touch pads didn't really fail, there was a Sirius XM update that bricked the system. Or maybe it was both. The axels I had too and if you had the design update (which you do now) they won't do that again.

 

CPO is more marketing than a regimented process. CPO also adds another 3-4K as they mark up any services.

I had issues within 1 week of ownership; granted it was with a W204 but it's still the same process.

I had two rear tires that needed replacement. I felt the rear was a bit fish tailing. Took it in and
their service dept. agreed. Then my iPod cable broke.

2 weeks after that the right front strut. They replaced both front struts. Car had 46,000 miles.

I'm now looking at a C400 and C450. It does seem that with the bi-turbo vs naturally aspirated, more maintenance is needed. The OP's list is pretty crazy and certainly unusual.

 

I think a lot of people have posted about the electric power steering clunk and replaced and replaced with no avail. Even me as a mb tech replaced ball joints, tie rods, control arms etc.
I See a thousand posts about this random clunking and people replacing CV even though it's obviously not a damaged CV, so here is MBs explanation. Keeping in mind the system needs over 400rpm and a SPD above 0 to operate and won't when the engine is off, also during hard turns when parking as it mentions.

Steering assist clunk

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