Misfire C180K

[Graham Spinks]

As the title reads, my 2005 W203 developed a misfire on No.1 cylinder. Subsequent investigation shwed that there was water in the plug well. I dried everything off, reassembled and now we are running sweetly again. The question is, "Where did the water come from?"

There's what looks like a joint face at the top of the well, but I've no idea what is involved if I need to strip this. Can anyone enlighten me, please?

 

[bembo449]

this used to happen a lot when I ran Renault 19's as they had a bonnet vent onto the engine to cool the manifold , it also allowed water onto the coil packs

 

[Wighty]

As the title reads, my 2005 W203 developed a misfire on No.1 cylinder. Subsequent investigation shwed that there was water in the plug well. I dried everything off, reassembled and now we are running sweetly again. The question is, "Where did the water come from?"

There's what looks like a joint face at the top of the well, but I've no idea what is involved if I need to strip this. Can anyone enlighten me, please?

View attachment 52217

Is the engine cover normally fitted to the top of the engine ? Has the engine been jet washed ? Have you driven through standing water ?
I would just run it now and check in a few days to see if all is dry still .

 

[Graham Spinks]

The cover has never been removed (at least, not by me). I've not driven through standing water or torrential rain and it certainly hasn't been jet washed (Note to self: I must clean the car sometime...)

I reassembled it yesterday and did an idling test, which seemed OK. This morning I went out for a short drive and still had the misfire. I fitted the spare coil pack I'd acquired, 10 minutes including cleaning up, and all now seems OK. I took it for a 60 mile round trip and it now is running sweetly again. Is there an O ring at the top of the well? I can't make up my mind what the tatty looking join is as I don't have any breakdown views of the top end.

 

[Oldspanners]

Can't see any water other than rain water getting in there unless someone was trying to clean up an oily mess. I had a problem when I first got my car where the seal around the oil filler cap had not been fitted right (not the one in the cap) and the ace spanner man who'd filled the oil on the pre-purchase service managed to fill up number 1 plug hole with oil.
All the seals and gaskets around there are for the rocker/cam cover and only oil would leak out. Once the water is dried out it should stay dry.
Good luck.

 

[Wighty]

The cover has never been removed (at least, not by me). I've not driven through standing water or torrential rain and it certainly hasn't been jet washed (Note to self: I must clean the car sometime...)

I reassembled it yesterday and did an idling test, which seemed OK. This morning I went out for a short drive and still had the misfire. I fitted the spare coil pack I'd acquired, 10 minutes including cleaning up, and all now seems OK. I took it for a 60 mile round trip and it now is running sweetly again. Is there an O ring at the top of the well? I can't make up my mind what the tatty looking join is as I don't have any breakdown views of the top end.

If it's the same or similar to my later CLK , there is a big gasket around the top cover of the engine with a small gasket around the top of each spark plug well . The tatty gasket you are referring to would involve more work to get to .
When you remove each spark plug coil , the two bolts on each coil are torqued to compress each spark plug top gasket .

 

[Graham Spinks]

It's of similar design except the mounting bosses are stepped up. At least it has been confirmed that if there is a leak from that sealing face it will be oil getting in there. No sign of that so I guess I'll just carry on and keep an eye on it. Thanks for all of your help