About to Buy C450: Can Owners List Their Issues?




I've read a lot of threads. it's not always stated what mileage the issue occurs at.
So rather than spend hours compiling or going on old threads for a reply,
I'm reaching out to the community for help, expertise, and advice.
For Example.
🚨 Issue: e.g. timing chain tensioner at 120k miles
Driving Style: Demonic Possession, Spirited, Old Man River, Grandma, Nun.Tune: Tuned, Not Tuned.
Many thanks!
TABLE OF CONTENTS (In Progress)
LED Door Lights DIY
Timing Cover, Cam Magnet Reseal DIY
Last edited by Nicholi2007; Aug 12, 2023 at 02:18 PM.
I've read a lot of threads but it's not always stated what mileage issue occur at. I've read some
disturbing things.
So rather than spend hours compiling, I'm reaching out to the community for help and expertise.
For Example.
⚠️ Issue: e.g. timing chain tensioner at 120k miles
Driving Style: Spirited, Demonic Possession, Old Man River, Grandma, Nun.Tune: Tuned, Not Tuned.
Many thanks
Issues: A/C doesn't blow cold, car shudders and vibrates only when accelerating, steering column height adjustment broken, radiator hoses pop off if you go over 140mph, 2x door handles lights stopped working, camshaft magnet cover oil leak, pan leaks, interior rattling. Never had had a check engine light ever oddly enough..
Driving style: Average for an AMG, nothing unsafe, no skids, burnouts or races, just quick short lived sprints occasionally.
Car is completely stock.
///Parts hard to find, I can't even find a pair of engine mounts..
you'll see with everyone else the main downfall of this car would be it's overall jerkiness, shakiness, weird because the car handles world class it's just not smooth.
I'm going to slowly week by week replace everything responsible for the steering wheel and cabin vibration in the front of the car like the transmission mount, flex disc, CV axles, driveshaft center bearing, tie rods and shocks. I can't tell if it's the tranny shaking or something with suspension but it goes to normal when you let off gas.
I would buy one only if you have $8000 to throw at the car the first year. Unfortunately it seems these newer Mercedes are designed to be thrown away after the exit the warranty period.
I previously owned a 1998 Sl500 r129 and a 1999 C230K Mercedes and they were absolute tanks in every regard.
Hate to say it cowboy this is a great value of a car and is a 10/10 on the fun factor and looks but it's a can of worms out of warranty.
The moonroof leaks water if you go through a automatic car wash. The water when pressurized and penetrate the seal if it is sprayed at certain angle. Ive had my shoulder drenched before.
Also the suspension rides like its on bricks, even in eco.
Also sometimes the AC smells bad.
Driving Style: Enthusiastic Dad, Properly warmed up, recommended service intervals (by kilometer)
Stage 1 EC with FI Exhaust.




- The jerkiness can be solved with a software update possibly. If that does not resolve it then it could be the transmission valve body.
- Engine mounts. Not sure where you're located. I did hear they were backordered last year but should be back now.
- A/C - Lots of reasons. AC evaporator, refrigerant leak, low charge. Even simple things such as fuse. Scan the car hopefully it throws a code.
- I heard door handle lights have been upgraded. Color is likely different though. I'd do all 4.
- Camshaft magnet cover oil leak is usually at higher mileage.
- I've heard pan leak. It's normally a bad seal. Hopefully not a bad leak.
- Interior rattling - Need felt tape.
- Shudder - It depends at what RPMs. When downshifting? It could be a bent rim or mounts.
Last edited by Nicholi2007; Aug 11, 2023 at 04:38 PM.
Quickly changed out from stock rims & runflats after purchase to a summer set up (Conti Extreme Super Sports w/19" TSW) and separate winter set up (Michelin CC+ on 18" Konig Oversteers. Get rid of (or store away/sell) stock rims and run flats as they just create issues & heartaches.
Driving style = ditto as waisoserious. Terribly important for the car's health/longevity to warm up all fliuds/oils to gray zone before switching to Sport+ asshat hooligan maneuvers. Like sex when you are old~




MB has upgraded the part. 19.20 to 22.00 each plus tax
099-820-01-83-64 (left)
099-820-02-83-64 (right)




Quickly changed out from stock rims & runflats after purchase to a summer set up (Conti Extreme Super Sports w/19" TSW) and separate winter set up (Michelin CC+ on 18" Konig Oversteers. Get rid of (or store away/sell) stock rims and run flats as they just create issues & heartaches.
Driving style = ditto as waisoserious. Terribly important for the car's health/longevity to warm up all fliuds/oils to gray zone before switching to Sport+ asshat hooligan maneuvers. Like sex when you are old~
Official oil change interval is 10,000 miles or once per year.
0W-40 or 5W-40 depending on climate. Higher altitudes should opt for 0W.
My View:
If you have tuned the car, I would definitely do it early. 5-6K. If it's a hot climate for extended periods of months,I would definitely do early.
I think one could safely go to 7,500 miles on stock (non-tuned) even if do you do a mix of casual and spirited.
I would stick to MB approved oil and filter only.
The only way to know for sure would be to do an oil analysis with blackstone.
I would get a MityVac extractor or something similar.
Last edited by Nicholi2007; Aug 13, 2023 at 01:10 AM.
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These cars are sensitive to having the required juice. Otherwise, things start to malfunction like the radio, A/C etc. Any AutoZone can test the battery for free.
It's very likely the battery needs replacement at 6 years. 4-5 years is average.
I usually buy the battery online and pick it up at the dealer as they normally discount parts. I just looked it up. Sale price is $251.18.
Thanks for the input.

Big thanks to a "Super Member" taking the time out to educate us newbies and share knowledge + empower the unwashed masses!
Yes, I suppose I am a bit crazy on the oil change interval of 5K. I figure it's going to hurt my pocketbook less keeping an expensive turbocharged motor bathed in fresh(er) oil than what Mercedes recommends. Chalk it up to PTSD from prior Subaru ownership.
The only unscheduled repairs have been cam magnet cover leaks and drive shaft guibos at ~85k miles. I think we're on the 3rd set of rear pads/rotors while the fronts were replaced once. This is my wife's car so driving style can only be characterized as "Elderly Grandmother."
- Second C400 was purchased in January 2022 with a hair over 40K miles on the clock (currently 49k miles). Was immediately taken to the drag strip and flogged. Then a JB4 was added and it was flogged some more, and then tuned via EC Houston and flogged some more (12.51@112.99mph).
I have developed cam magnet cover leaks on driver side, which I'm going to do myself.
The car had nearly new Bridgestone run flats on it when I bought it, and they're almost shot already. Plan is to get Kmac adjustable bits and have it truly aligned when I put some Vredestein Quatrac Pro tires on it.
Overall assessment: absolutely fantastic cars that are an amazing performance/comfort bargain.




As for oil it's better to be early than late. Spark plugs I'd do at recommended mileage.
Carbon buildup is inevitable but on time maintenance is key.
- The jerkiness can be solved with a software update possibly. If that does not resolve it then it could be the transmission valve body.
- Engine mounts. Not sure where you're located. I did hear they were backordered last year but should be back now.
- A/C - Lots of reasons. AC evaporator, refrigerant leak, low charge. Even simple things such as fuse. Scan the car hopefully it throws a code.
- I heard door handle lights have been upgraded. Color is likely different though. I'd do all 4.
- Camshaft magnet cover oil leak is usually at higher mileage.
- I've heard pan leak. It's normally a bad seal. Hopefully not a bad leak.
- Interior rattling - Need felt tape.
- Shudder - It depends at what RPMs. When downshifting? It could be a bent rim or mounts.
https://youtu.be/YPLZxADQ-qM
my a/c compressor's clutch doesn't pop out and looks like it's melted, worked on the hottest day this year, next morning wouldn't go cold. I'll figure that out later, I want the car to at least be enjoyable...new tires all the way around, new rotors .




my a/c compressor's clutch doesn't pop out and looks like it's melted, worked on the hottest day this year, next morning wouldn't go cold. I'll figure that out later, I want the car to at least be enjoyable...new tires all the way around, new rotors .
- I'd scan the car with an OB2 otherwise you won't get a proper diagnosis. It could be the clutch. It could be a bad relay or the A/C pressure switch.
- Under center arm rest would be transmission mount. I would upgrade this part to the C63 version which has more rubber. It will last longer. Yes it's more money.
addendum: Look for a polyurethane mount.
Last edited by Nicholi2007; Aug 18, 2023 at 04:51 PM.








Also, as mentioned in another thread, this car had its transmission replaced with very low mileage, like less than 5,000.
Last edited by GermanCarShow; Aug 18, 2023 at 10:44 PM.




I've even read about a headlight control module fail. Many are minor.
The major issues centered around the transmission.
A dealer is trying to sell a nearly fully loaded C450 for 25,600 with 77K miles.
No 360 camera or heads up display but everything else.
I'm trying to get them down as things are definitely going to fail in the near future.
Tough to find a 6 with the options I want for 20K. At least there's a record of the transmission done.
Last edited by Nicholi2007; Aug 19, 2023 at 10:45 AM.




1. Possible Check Valves and Chain Tensioners. Per MotorReviewer M276 Reliability
Remember that direct injection nozzles are sensitive to fuel quality. Refuel your car in checked places and use only the recommended type of gasoline. Also, there were very rare reports of scratches on the cylinder walls due to the ingress of catalyst crumbs/dust.
The approximate lifespan for the turbocharged 3.0-liter and 3.5-liter versions is 160,000-180,000 miles (250,000-290,000 km). Naturally aspirated versions usually reach 200k miles mark. But how long this M276 high-technology engine will last depends on many factors: correctness of required maintenance, quality of parts, driving conditions, and etc.
3. Per @mikeyvol comments on camshaft adjuster issue

I've never had any warranty on my naturally aspirated cars but I will with the bi-turbo. See this post that takes a dive on common M276 engine problems.
Last edited by Nicholi2007; Aug 25, 2023 at 05:38 PM.
my a/c compressor's clutch doesn't pop out and looks like it's melted, worked on the hottest day this year, next morning wouldn't go cold. I'll figure that out later, I want the car to at least be enjoyable...new tires all the way around, new rotors .
If you coast the car is normal, it kinda jerks a tiny bit when you gas or let off gas (feels like engine is rocking)
I checked the engine with hood up and gassed it and the driver side of the engine went up and the left stayed put.




If you coast the car is normal, it kinda jerks a tiny bit when you gas or let off gas (feels like engine is rocking)
I checked the engine with hood up and gassed it and the driver side of the engine went up and the left stayed put.
I will be doing the repair myself and will probably record it since there is no video in existence of the procedure.
I used to have the Mercedes wis on my laptop but it got accidentally erased. Anyone know what the transmission mount part number is for certain?
Btw, I also tried to wiggle the main driveshaft under the car it it didn't feel like it was loose, if it was, the center support bearing would've been the culprit.
I know I've got to replace the engine mounts too because the driver side lifts quickly only on that side of the engine when you press the gas while looking at the engine with the hood up.
The engine mounts were replaced 3 years ago according to previous owner paperwork, no mention of transmount however




I will be doing the repair myself and will probably record it since there is no video in existence of the procedure.
I used to have the Mercedes wis on my laptop but it got accidentally erased. Anyone know what the transmission mount part number is for certain?
Btw, I also tried to wiggle the main driveshaft under the car it it didn't feel like it was loose, if it was, the center support bearing would've been the culprit.
I know I've got to replace the engine mounts too because the driver side lifts quickly only on that side of the engine when you press the gas while looking at the engine with the hood up.
The engine mounts were replaced 3 years ago according to previous owner paperwork, no mention of transmount however
If you coast the car is normal, it kinda jerks a tiny bit when you gas or let off gas (feels like engine is rocking)
I checked the engine with hood up and gassed it and the driver side of the engine went up and the left stayed put.



