Got a c300 yesterday, had a couple of questions
I have a warning for all the light bulbs when I start the car, first its front lamps, then if I push the brake I get brake light warnings, the light work and the owner said he changed all them out, what can I check? Can this be a fuse or relay issue?
When I set lights to "Auto" they are on even when it's sunny, is there a setting for this or do I just need to clean the sensor on the windshield?
The car has a very slight vibration when at a red light, if I put it in neutral it stops. From my research I found this might indicate motor mounts, would be be correct?
When I turn the wheel or when I set off from a red light the car creaks, from reading up on it, it might be dried out ball joints. or the strut bearings. I also have a warning for brake pads, I will be changing out the brake pads today but feel as though they are not related to the creaking because it also happens if I just turn the wheel. Anything I can do about this without changing suspension parts?
I know someone would probably say I should have looked for one without any issues but I got this as a temporary car because my car needs to get fixed after an accident and this was local and wasn't that expensive and seeing as there's no codes on it for a while and a decent service history, I felt it wasn't too bad. Really appreciate anyone chiming in on what I can check and fix. Thanks




for the headlights being on, is it just in auto or even when off? i ask because maybe the drl is on. Do you have the operators manual in the glove box, if so page 91 on lightiong, then page 133 for getting into the lighting menu to check the settings.
Vibration, could be a few things. Mine was running a little rough at stop lights, put a bottle of techron in and now it runs great again. Or check your mounts, have someone rev the engine while your in the engine bay watching the engine for movement.
Creaking, good luck. Mine creaks on the front right side. I go under the car and spray all the ball joints and bushings with some PB Blaster silicone lube and it takes care of most. The bushings do look fine, but the car is old and has alot of miles. Winter/cold weather seems to make things louder.
I dont see these things as big issues. With a little time and looking around you can fix them.




https://www.mbusa.com/en/owners/manuals
There is a recall on the rear light bulb carriers. Not sure if its related to your warning light issue.
*Edit. I would really take a good look to make sure all the bulbs are in fact working. i did a quick search for the bulb out warning issue and seems a few people ended up with bulbs that were in fact out and they didnt notice until it was night time.
Last edited by TimC300; Sep 19, 2023 at 01:54 PM.
If the previous owner replaced all the bulbs, make sure they are the ones specified by the owners manual and not some LED "upgrades". (Again, as Tim said.)
You can always check for bad motor mounts by putting the car in gear, hold the brake firm, and give it a little gas. Have the hood open so you can see if the engine rocks significantly. (Search youtube for videos about this.)




heres a sheet telling what bulbs are required. This is for a 2010 C300 4matic sport but im assuming it should be the same.
I went and looked up the spec for each bulb which is why I wrote them down. Alot of bulbs have the same base or even look the same, but they have different wattage which can throw things off and get warnings popping up. All of the above bulbs work perfectly from my experience. I went and replaced most of them, keep the old bulbs wrapped nicely in the trunk behind the fuse panel in case one goes out at night and I need to replace, to keep from being pulled over mostly. I even have a pair of spare H7 bulbs for the low beam and/or fog light. But I did install an hid kit for the lows, when I first got the car I couldnt see anything driving at night the halogen lights they are so bad in my opinion. Thats simple plug n play so i can easily swap in the H7 if needed quickly.
These are the majority of the bulbs in the rear, I think 4 each side.
* The blue bulbs are the original Mercedes bulbs. 1 bulb in each side of my car burned out so i replaced with just regular 2825LL bulbs, which look brighter. I ended up just removing the other 2 blue bulbs and replaced them all so they look the same. If you want the Mercedes bulbs they have them on FCP Euro for a few bucks each.
These are for the front parking lights (eyebrow), license plate, and front side marker. Think these are also used inside the car.
Front and rear turn signal bulbs.
Just for fun ill show what I have in my fog lights. I was searching around for the brightest whitest H7 bulbs, that wont burn out every year and came across these. Ive had Silverstar Ultra in previous vehicles and these seem similar but less expensive. They are definitely brighter and whiter than the stock bulbs that were in there.
Last edited by TimC300; Sep 19, 2023 at 03:50 PM.
heres a sheet telling what bulbs are required. This is for a 2010 C300 4matic sport but im assuming it should be the same.
I went and looked up the spec for each bulb which is why I wrote them down. Alot of bulbs have the same base or even look the same, but they have different wattage which can throw things off and get warnings popping up. All of the above bulbs work perfectly from my experience. I went and replaced most of them, keep the old bulbs wrapped nicely in the trunk behind the fuse panel in case one goes out at night and I need to replace, to keep from being pulled over mostly. I even have a pair of spare H7 bulbs for the low beam and/or fog light. But I did install an hid kit for the lows, when I first got the car I couldnt see anything driving at night the halogen lights they are so bad in my opinion. Thats simple plug n play so i can easily swap in the H7 if needed quickly.
These are the majority of the bulbs in the rear, I think 4 each side.
These are for the front parking lights (eyebrow), license plate, and front side marker. Think these are also used inside the car.
Front and rear turn signal bulbs.
Just for fun ill show what I have in my fog lights. I was searching around for the brightest whitest H7 bulbs, that wont burn out every year and came across these. Ive had Silverstar Ultra in previous vehicles and these seem similar but less expensive. They are definitely brighter and whiter than the stock bulbs that were in there.
When I’m doing the front brakes in the next couple of days I’ll check all the ball joints maybe spray some on silicone just to see if it helps, can’t hurt I guess, and the rear sub frame for rust. I’ll also register to check recalls. When going over bumps there’s a slight noise from what I found it might be the strut bearings. Like everyone pointed out it’s not things that make the car un-drivable more like cosmetic or ride quality. Just wanted to see how I can clear the bulb faults and how severe the creaking and engine vibration might be. Other than this the only other “problem” is the driver seat tear but I’ve been a basically most of these c300 have this problem. I ordered the bottom seat cover in leather, it says it fits 2010-2014 seat but they look the same. It’s worth a try. I also got some Techron, might try that.




Im always inspecting things when working on the car. I like to use my phone to take photos and then view the photos on the computer so i can zoom in. Lets you really see anything damaged, broken. check all the bushings for cracks, ball joints for leaking grease, etc. Grab a pry bar and try to move move the control arms listening for noises. Then the silocone lube does quiet squeeks. Check the sway bar links for movement, i changed mine due to them clunking over bumps.
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Silicone spray works wonders on aging bushings. But it won’t help ball joints that have gone dry and started to groan. Try the spray on the bushings first. Don’t forget the shock tower. If that doesn’t help, what you can do for ball joints is get a small one-handed grease gun and clip in hypo needle. Stick the needle into the ball joint boot and inject enough grease to see the boot swell a bit. Don’t overdo it or the boot will pop off. That will quiet ball joints for 3-5000 miles.
The car has 137k miles. If it hasn’t had the engine and transmission mounts changed, it’s a certainty that they’re bad. A C300 should be smooth as silk.
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Silicone spray works wonders on aging bushings. But it won’t help ball joints that have gone dry and started to groan. Try the spray on the bushings first. Don’t forget the shock tower. If that doesn’t help, what you can do for ball joints is get a small one-handed grease gun and clip in hypo needle. Stick the needle into the ball joint boot and inject enough grease to see the boot swell a bit. Don’t overdo it or the boot will pop off. That will quiet ball joints for 3-5000 miles.
The car has 137k miles. If it hasn’t had the engine and transmission mounts changed, it’s a certainty that they’re bad. A C300 should be smooth as silk.
When I was in the car earlier i did get the 4 fault on the dash they were, front brake wear, auto headlight inoperable and rear left lamp and brake light and rear right lamp and brake light. Pretty sure I saw "front" earlier today, maybe it didn't pop up now because the front light were off. Hopefully the sensor "relearns" so I can get that out the way or maybe end up replacing if it doesn't but I will go and check wattage of bulbs based on the sheet provided.




https://www.pelicanparts.com/techart...ld_Removal.htm
I was going to mention putting a bottle of Techron in the gas tank when you said there was a slight vibration. My car felt like it had a rough idle when at stop lights so i put a bottle of techron in the tank and now its running fine again, I even noticed it seemed a little quicker, not more HP wise but inthrottle response. They have it on sale at Napa auto parts if theres one near you. I have been using techron for years now, I only think about it when the idle seems a little rough usually at stop lights, put a bottle in and I totally forget about it, seems to work.
I havent really looked through all your codes, have to run to the store. ill look when I get back on.
*for the tail lamps have you taken the bulb units out to inspect them? Could be corrosion and needs a cleaning.
Last edited by TimC300; Sep 22, 2023 at 03:28 PM.




Heres a good thread on the P0521 code. Has the fix, in there case.
https://mbworld.org/forums/e-class-w...or-0521-a.html
For the stored codes I also had a few when I first hooked up my recent scanner, I erased them and they haven't come back since. I do remember the abs warning light coming on awhile back, was just a one time thing and probably why the code was there.
I had this, erased and hasnt come back.
And back to the tail lamps. Ive read a few people have had issues with the tail lamp carriers and/or wiring harness. Partly why they had a recall, as i noted above. inspect the harness for melted plastic. Inspect the carriers for corrosion. Double check for burned out bulbs. I guess its so common FCP offers a repair kit that has new carriers, connectors, pins and grease.
This photo is from someone with a tail light issue.
Last edited by TimC300; Sep 22, 2023 at 10:13 PM.
Heres a good thread on the P0521 code. Has the fix, in there case.
https://mbworld.org/forums/e-class-w...or-0521-a.html
For the stored codes I also had a few when I first hooked up my recent scanner, I erased them and they haven't come back since. I do remember the abs warning light coming on awhile back, was just a one time thing and probably why the code was there.
I had this, erased and hasnt come back.
And back to the tail lamps. Ive read a few people have had issues with the tail lamp carriers and/or wiring harness. Partly why they had a recall, as i noted above. inspect the harness for melted plastic. Inspect the carriers for corrosion. Double check for burned out bulbs. I guess its so common FCP offers a repair kit that has new carriers, connectors, pins and grease.
This photo is from someone with a tail light issue.
As for the lights, I'll check tomorrow for the carriers having any signs of damage but might hold off on replacing bulbs because they work for now and after seeing the code for a faulty rain/light sensor I'll replace that first. That's also the first fault that pops up as soon as I start the car "Automatic light inoperative".
I ordered one, should be here next week, if faults still show up I'll start going bulb by bulb.




I seem to have signs of oil all over my intake manifold im trying to find the cause of. i will say if I had replace my manifold i would most likely get a used one off ebay, i already have a few lined up in case. Found a few low mileage, well much lower than what my car is anyways, and they look very clean no oil. And some come with everything, fuel rail, throttle body, fuel injectors, basically look bolt on and go minus ecu. Some people arent comfortable buying used, ive had very good luck so far.
For the tail lights im just saying remove the carriers and look around, can easily tell if the wrong bulbs were installed just looking. Look for corrosion. The carriers pop right out, just push the plastic tab up, or down I forget and they come right out.




Heres the article: https://blog.fcpeuro.com/solving-fai...ODYwLjI3LjAuMA..




I have no problem buying used parts, most times I feel better buying a used OE part than an aftermarket part. Perfect example is my purge valve, my car had a check engine light and the most common issue with that code seemed to be the purge valve which i then confirmed by listening to it and it was not working, no continuous clicking sound. Bought a used Mercedes purge valve off ebay for something like $12 shipped and its been working great for 2yrs now. When looking for a replacment I just made sure the seller was not known to sell junk parts.
Since seeing oil residue on my intake manifold i have been looking around at used replacements. I have a few lined up from one specific seller i bought from before with very good luck. They are around $200 and come with everything still attached, throttle body, injectors, fuel rail, even the ecu brackets and mass air flow sensor. They look very clean, no signs of oil. Im not saying this is the way to go, but I probably would go this route. the id have a bunch of extra parts along with it, the extra injectors alone is a great plus. I can tell you where im looking if anyones interested.
Same with the slk350 throttle bodies, i havent done much research on if used are the way to go, but i found a bunch that look clean that would be worth looking in to.
https://youtu.be/oMcPzf3b3N0?si=oCWc90Q0Kstj0VRY





