f20inmi

My C300 with 53k miles set the crankcase over pressure warning for a second time. First occurrence resulted in a SES light and huge plumes of the foulest white smoke a couple weeks after the code 1st displayed. The Iowa City dealer retrieved the car with flatbed, said it was a known problem that is addressed with a cold weather kit. The valve is "buried deep" so they pulled the turbo/intake/installed the valve/etc. and sent me on my way. 4 months pass and the SES light displays yet again. Turns out it is the same crankcase over pressure code. I was in Chicago so I dropped the car at the dealer they confirmed this. They quoted $2k to complete the repair.

Has anyone else had a similar issue?

From my point of view I have a couple options... I will contact the Iowa City dealer and ask if they will step up and help me out with the repair since it appears to be a reoccurrence of an issue which should have been addressed within warranty. I suspect this will be long shot but who knows.

I don't mind wrenching on this stuff myself, but tech manuals seem to be unavailable to the general public. Where do folks find tech information?

Thanks in advance.

Sador Efrem

Hello sir,

I recently had the same issue with my C300 and it is just out of warranty. The problem occurred before the warranty expired but it was intermittent and the one time I left it at the dealership overnight, the CEL was gone in the morning. It got worse recently and they quoted me 1700CAD to fix it but told me to come back if it is on all the time. A few days ago, the light came on and the car stalled on me a couple of times and there was an oil leak under the hood with white smoke coming out of the exhaust and a burning oil smell. I took it to the dealership and they haven't looked at it yet but I wanted to get your input as the problem is the same issue you had with the white smoke.

And what did you end up doing regarding the warranty? I had an indie mech tell me that he was trying to get it fixed under warranty from a service rep he knows as the problem is a known issue for those cars.

f20inmi

It appears to be the same issue. First the good news, mine has not repeated since the last repair. The dealer said it was tied to the cold weather, was a known problem and was addressed by insulating the valve. The second repair was covered under warranty since the first repair took place within the car's original warranty period. The dealer warrants their repair for 1 year or 12000 miles. When I checked my repair bill it was in the $ range you mentioned. It is an extensive repair that requires removal of many parts.

redsly

If this is the concern I am thinking of, and see constantly, the procedure requires removal of several items to include the left engine mount.
I've always believed it to be induced by the cold weather and condensation in the valve/vent line. I live in the North East where it gets cold too. We get some valves with an insulation wrap/tube on them and some without...
I had a '15 C300 and always let my car reach operating temperature before driving. I also drive the highway everyday. I feel that I see this issue more common on vehicles that don't appear to often drive many miles.
I actually had one yesterday where the valve was stuck and the engine oil had actually coated the intake pipe and turbo. This could have been why you seen smoke, but I've never seen smoke or drive-ability concerns from it.
Just two cents on this.

Sador Efrem

Thank you all for the information. The issue was the crankcase vent valve as suspected. The tech said something along the lines of the valve being stuck and was sucking the oil back in. They replaced the valve and did the work under warranty and the car runs fine now. Thank you again.

hihahi45

So an independent mechanic replaced the crankcase valve under warranty? How does that work? I thought you can only get under warranty work done at the dealerships.

hihahi45

Hi, how much did the repair cost?

2016C300W205

Had the same issue as everyone else, but worse.

- CEL on at 91,000km but went away after a day. Code was for “crankshaft rebreather valve” but since light was off, kept driving
- Week later mid-drive, started running rough and next intersection started blowing very thick white smoke out exhaust.
- Flatbed to dealer, needed a new engine as cylinder 1 had zero compression and had scratches on the cylinder wall.

Story has a happy ending after all, but was without the car for quite a while.

Edgrrr

@redsly Do you have the part number for the insulated valve and line? I have a 2015 C300 4Matic in Quebec and I do not want to get into it without the best part for the job.

GringoBling

sometimes emissions parts have longer warranties

W205_Merc

Mine happened at around 43K miles and was a related issue as you stated. Thankfully it hasn't come back yet and im at just about 60K miles