Replaced the cylinder head cover gaskets and spark plugs on my 2013 C250 last week. Oil had been leaking slowly for some time but was becoming more noticeable. The gasket around each coil had failed and all of the spark plug holes were filled with oil. The old gaskets were like hard brittle plastic and broke apart during removal. Project was straight forward and took a couple of hours. Most of the time was spent cleaning the gasket surfaces, coils and removing any oil from the coil and cover bolt holes. Had a nice big smoke screen on the first engine start from all the oil draining into the cylinders when the spark plugs were removed!

2013 C250 188,270 miles

 

I have done this a month ago and in the process I managed to break the right side chain guide. I rigged it to stay in place and put everything back in with new gasket and seals.
I will redo it soon to replace the broken chain guide, so I will be doing all new seal and gaskets again along with chain guide.

 

Looks like we'll both have to redo the project. Just checked my pictures and the top of the right side chain guide is broken off. I didn't find any loose parts so these might be in the oil pan. I believe these upper guides are separate from the main lower chain guides and I'm hoping these can be replaced without removing the front timing cover.

Man, I was so careful this time and thought I had finally successfully completed a job on this vehicle without breaking something or having to buy additional unexpected parts.

 

Yep, I ordered and got 4 pcs of chain guides so not reason to reuse a broken one.

 

The left and right hand parts are referred to as Chain Sliding Rail Skip Protection in the parts manual and just plug into the top surface of the cylinder head (part #30). They are separate from the main chain rails. Ordered two this morning (plus new gaskets and seals).