Hi guys, Im new here and wanted to get some input on my current situation *This will be a long read so I apologize in advance while I am also not a mechanic nor knows anything about cars)*

I purchased my car from someone and they claimed of course nothing was wrong with the car... Boy was that a lie but hey you live and you learn..
I have a 2012 c250 that currently has an Oil Leak and Misfiring..
My car has been leaking oil for a while now and I haven't been able to fix it YET due to not having the funds. My car however was running fine until recently. While I was on my way to work, I notice my car started shaking during start up and I could barely drive it due to loss of acceleration.. So I left it alone!. I was talking to my landlord and he guessed that it was my spark plugs that needed to be changed. My car currently has 130,000 miles on it. I purchased a scanner just to make sure and the scanner stated I had a misfire on Cylinder 4 and something was wrong with the ignition coil(D). So my landlord helped me with opening up my I guess Gasket (not sure if thats the right word sorry) to access the spark plugs and coils. We notice oil were filled in 3/4 of the cylinders! so we replaced ALL of the spark plugs (NGK) and Coil D (I purchased Carquest since it was the cheapest). He did some type of test where you turn your car on and unplug the coils one by one and if your car responds (shaking I guess), its a good sign.. Well all of the coils responded except for coil D, so he said that might be an issue (he's not a mechanic but he knows a little bit about cars). Afterwards, I did a test drive and the car was running ok... until the next morning. Once I started the car the shaking came back! So I left my car alone and contacted a mechanic to check out my car. The mechanic came and stated my valve cover needs to be replaced and due to oil getting inside the cylinders, its causing the shaking (misfire). I did ask him if my valve cover is the reason behind my oil leaking and he stated Yes! He also notice the the issue with coil D was not responding and stated I need a new coil as the Carquest coil is not working for my car! He removed coil D completely and left the other coils along with the spark plugs and said for me to return the coil and exchange it for another brand. I said okay cool, and left my car alone. I have not touched my car since!
NOWWWW, here is where I am actually getting concerned, I had turned my car on for the first time since my mechanic came (its been about a week later) and my car literally turned on, did the shaking then shuts off all within seconds (this was NOT happening before).. I plugged the OBM scanner and now its saying new codes: Multiple misfiring, Issue with coil A and D along with about 3 cylinder issues..

Could him removing Coil D from my car cause all of this (since its happening now that he removed)??? Is this now a more concerning issue or it is really just an easy where I should replace ALL coils and spark plugs?? (Im suggesting ALL because I dont know when was the last time the previous owner did a tune up)

**Also, I haven't drained the oil since it is overfilled and removed the spark plugs nor coils so im not sure if oil leaked inside again**

 

It’s a 4 cylinder engine, so one cylinder misfiring will shake like it’s coming apart.

But let’s go back to basics and move forward from there.

You say the oil is over filled? That’s number 1. Overfilling oil can cause lots of things like overwhelming the crankcase ventilation and causing high pressure, which could lead to the leaks you see. Drain and refill the oil to the correct level. Also note the oil for signs of moisture, like milkiness.

Next. Spark plug holes filled ¾ with oil is far, far, from normal. Each plug hole has a gasket at the bottom sealing the valve cover to the head. Leaks here are not uncommon, but the oil overfill may have made matters worse. It would have been a good idea to stop at this point and correct this before going on. You probably just need a new set of valve cover gaskets and not a new valve cover, but inspection after it’s removed is needed. Part of the crankcase ventilation system is in the valve cover, too.

Now for the bad coil(s). Coil D was probably bad. But it may have been the very high oil level in the plug hole that ruined it. I’ve maintained a lot of cars, and a lot of these 204 chassis Mercedes. But something I’ve never done is start one with one of the coils removed. So I have no idea what the results would be. I’m sure the ECU wouldn’t be happy, but I doubt you damaged anything that wasn’t bad before.

1-Get the oil level right and the valve cover leaks fixed at the same time without starting the car. 2-Then get a new coil D. It’s not necessary to buy a Mercedes coil, but get a Bosch or Beru coil. They’re nearly identical to the Mercedes ones. 3-Make sure the oil level is correct, put in 4 new NGK or Bosch spark plugs, and the new coil D. 4-Now it’s time to start the car, see how it runs, and connect the scanner* to see if there are any error codes.

*Most inexpensive hand held code readers are not scanners. They just read generic codes for the engine. To really diagnose a Mercedes you need a dedicated Mercedes scanning tool. Many forum contributors use iCarsoft MB v3.0 or Foxwell scanners. I have an Autel multi vehicle programmable system which YOU DON’T NEED.

Wait for a few other members to reply because they have different perspectives. Then proceed to get your car together. Don’t be afraid to ask questions. Trolls are pretty rare here.

 

I'm sorry need to say this, but people who buy an older used Mercedes thinking they are getting a great car for cheap soon realize that it is still an expensive car to keep and maintain, especially for people who are not able to do their own maintenance and repairs.

You have a 12-year-old car with 130,000 miles on it. That's not old and not excessive miles for these cars IF the car has been well-maintained during those miles. However, if some key maintenance items have been neglected, such as oil changes, transmission services, and brake fluid changes, your risk of future problems has increased significantly.

It's a little late to get a pre-purchase inspection done, but you may want to get an assessment of the condition of the car from a qualified Mercedes mechanic who is familiar with the model and year of your car. At least you'll know what to expect going forward.

My first Mercedes was a 2004 SL500 with 50,000 miles and 13 years old at the time. It had been religiously dealer maintained. A friend who was a Mercedes mechanic told me the issues I would have with the suspension, roof, and other major components in time. He was right about the suspension, so I traded the car before his other predictions came true.

It's going to be a painful decision, but if you are finding it hard to afford now, it's not going to get any easier.

Good luck.

 

Buy an OE coil. Either Mercedes brand or I believe Bosch makes the Mercedes coils. Double check I could be wrong.

As someone said above im not sure that you have to replace the entire valve cover, may just need new gaskets. Ive read many posts where people just replaced the gaskets and solved the oil leaks.

Why is the oil over filled? Drain off the extra oil asap. Either suck it out the dipstick, or open the drain underneath and let a little out at a time and keep checking the level. Im not sure about your specific engine but with mine there is a circle mark on the dipstick right between the Min - Max marks, proper level is right in the middle.

Invest in a mercedes specific obd scanner if you dont have one. I hear the Launch Creader Elite is good. Do the repairs first then if there are still issues think about getting one.

I would not start the car until the repairs are done.

 

Thank you!!! In regards of the COILS since its now A and D.. Should I just buy all 4 new coils to be on the safe side or just replace those two?

The oil looks fine. No milkiness or weird look to it.

Also, Im still trying to understand the difference in the spark plugs along with gaps?? because some are cheaper than the other. I rather go with the best route rather than the cheap route. Ive been searching online in so many fourms to see which spark plug would go best with my car but I have yet to find an answer. I seen people recommend both NGK or Bosch but not the exact plugs or maybe I overthinking it?? I seen people say you have to make sure the gap is right.. Idk what that even means lol im just trying to learn as much as I can so I can at least fix up my car so I can drive it to work, save up and get a new car :/

I was FCPEURO, and seen a set of 4 new coils (beru along with 4 spark plugs NGK)
I figured ill be going with BERU since that was originally in my car however for the spark plugs I threw the old ones out not knowing or thinking it would have the part # (if it does) ..
These are the spark plugs it comes with: https://www.fcpeuro.com/products/mer...plug-ngk-94716
I just want to make sure im getting the right parts.

 

I accidently overfilled it when it was low on oil. I didnt even notice until my landlord pointed it out.

Thank you!! Im going to drain it out completely, do the repair then see. Im crossing fingers lol I didnt even plan on having this car for long as I just needed a cash car that was nice for the moment until I can save up and get a new car. :/

 

Look in your operators manual in the glove box. It may list the type of spark plugs in the vehicle specifications section. Mine does, I have a different engine so yours is probably different. Mine says Bosch then lists the part #. Also lists the spark plug gap. The entire section has alot of useful info, like drive belt size, spark plug firing order etc.

I personally wouldnt replace the coils unless I knew they were bad. Obviously replace the off brand coil.

The problem with over filling the oil is over time it may force its way into the pcv system, which happens to be in your valve cover. If the oil was recently done theres no need to waste it, just drain some off if you can.


Heres what my 2010 Operators Manual has for the C250.

 

Good result on the oil.
You may as well get the FCP Euro plug and coil kit. If you decide to keep the car for a few years, that’s one less worry. The boots were sitting in oil, so they may be compromised anyway. Spark plugs are changed every 60,000 miles in your car.
The NGK spark plug is 94716
The Bosch spark plug is 8132
The numbers on the plugs themselves are technical manufacturing info.
Both of these plugs come pre-gapped. Do not try to regap them. (Some people will argue with me about this).
Mercedes uses both Bosch and NGK spark plugs at the factory. (Some people will argue about this, too).
There are more expensive spark plugs that won’t do anything better than these in your engine.
You probably don’t have a small torque wrench rated in inch pounds or deci newton meters? You’re screwing into an aluminum head and don’t want to strip the threads, but need to get the spark plug tight. Don’t panic if you don’t have one, there are ways to get the plug tight and stay safe. Most NGK plug boxes have the method described on the box. And don’t use lubricants or anti-seize on the threads.

 

I recommend always using a torque wrench when working on the car. I just have the inexpensive harbor freight ones, paid around $12 each during a sale. I had a habit of putting bolts on way too tight.

Spark plugs should be pre-gapped, but I always double check with a cheap .99 cent gapping gauge.

 

There is nothing wrong with buying a used car if it has been well cared for. Based on the cost of new cars and the problems that seem to come up, a tested and proven older model may actually be a better purchase. It seems there has been a rush to market new technology that is yet to be proven. I'm not an early adopter type anymore. I'm older now and have learned my lessons. As long as you go into a decision with your eyes open (and emotions suppressed), you'll probably be OK.

 

Thank you!!

 

Thank you! I started adding all the tools in my cart lol