rusty residue around cyl 5 sparkplug... headgasket?

[ATB88]

Swapped out spark plugs and coils today, and everything was going great until I got to cylinder 5 -- a bunch of white and rusty residue at the bottom of the spark plug well and around the base of the spark plug. Plug has probably ~10k-15k miles on it. The actual electrode end that sits inside the cylinder looks fine, but I'm pretty worried about the rustyness -- looks like a lot of moisture got in there somehow. Is it possible that there's a way the headgasket could be leaking coolant into the sparkplug well? Photos below! All of the other plugs are fine. How worried should I be and what should I check? Car is running fine.

[Arith2]

You need to figure out what seal is leaking in your engine bay. The head gasket doesn't have anything to do with spark plugs. The bottoms are untouched from corrosion. Looking for dried water trails that lead to dripping in that spark plug tube. Also, replace that plug and coil at a minimum.

[bmwfnatic]

You are probably just fine, perhaps some water sat in there for a while, just replace the plug and probably also the coil and check back in a while if it has happened again, probably not.

[TexaZ3]

Likely just some water/condensation that was sitting on top of the plug - did you wash your engine recently?

[George Hill]

Do you keep the black valve cover trim on or off?

[eacmen]

Do you run with the black beauty cover on the valve cover? Not sure how water would get in the spark plug wells with the beauty cover on.

[sapote]

a bunch of white and rusty residue at the bottom of the spark plug well and around the base of the spark plug..

Water pooled in the hole for sometime. I'm surprised that no engine misfired code during the time. Just clean up the parts and everything should be fine if they haven't broken yet. But you need to find how water got in there.

[Lavatoad]

Do you run with the black beauty cover on the valve cover? Not sure how water would get in the spark plug wells with the beauty cover on.

This is why I put the beauty cover back on my track car. Water was working it way past the coil.

[ATB88]

Thanks for the thoughts, everyone.

So, there was probably a 6-12 month period last year where I was running it with the engine beauty cover off. Didn't seem like it mattered, since the coils make a seal at the top of the spark plug well, and it didn't seem like it would be possible for enough water to accumulate up the top of the spark plug well where it makes the seal with the ignition coil anyway. But this would support why cyl 5 is the only one affected: it sits directly beneath that perforated plastic vent near the back of the hood.

Is it possible, perhaps, that some accumulated water sat around pooling outside of the spark plug well, where the spark plug well goes into the valve cover, and leaked into the spark plug well through the spark plug well seals that sit between the valve cover and head? This is a scary prospect if true, because if water leaked into the sparkplug well, then that suggests that water could have just as easily leaked into the valvetrain. Yikes. Thoughts? Car runs well, so no reason to believe this has caused any catastrophic issue, but scary to think about nonetheless.

I'm currently inclined to believe that this is the result of leaving the beauty cover off, but if anybody has any suggestions otherwise I think I should consider them. Relieved to hear that this doesn't line up with a headgasket issue, though, and that it wasn't coolant.

[Arith2]

I haven't had a beauty cover on my engine in 4 years and water has never pooled in any cylinders. It's my daily and I live in FL. Do a water test with a water hose. I've seen multiple BMWs have this issue. This is the first E46 I've seen but people typically aren't bring an E46 to the dealer. It may be helpful to just replace the seals around the drug bin and the water drain out of the microfilter housing. I'm not certain if the seal on the tray or the drains can be ordered separately.

[ATB88]

Thanks for the insight. To clarify: I spent some time running without the microfilter housing while I was also running without the beauty cover. Assuming you haven't been running without your filter housing, this could be it. Water test with a hose isn't a bad idea, although I'm still paranoid that if water is leaking into the sparkplug well then it could also be leaking into the valvetrain area (which I can't see).

[George Hill]

I spent some time running without the microfilter housing while I was also running without the beauty cover.

Bingo.

The spark plug well is separated from the valvetrain, otherwise the spark plug would be covered in oil.

[sapote]

Thanks for the insight. To clarify: I spent some time running without the microfilter housing while I was also running without the beauty cover. Assuming you haven't been running without your filter housing, this could be it. Water test with a hose isn't a bad idea, although I'm still paranoid that if water is leaking into the sparkplug well then it could also be leaking into the valvetrain area (which I can't see).

The aluminum valve cover has 6 rubber ring seals to seal off the plug wells from the valvetrain chamber.
without the cabin air filter tray, then rain water can cover a section of the engine, and the hot engine oil smell must be strong in the cabin.

[ATB88]

Ah okay, looking at some pictures I think I see why the water goes in the sparkplug well and not the head -- the water doesn't have to get past the seal to get to where the sparkplug well meets the head.

Sapote, there was never anything noticeable in terms of either smell or durability -- I suspect because this happened from the car sitting parked in the rain, not driving in the rain.

New question: is there a good way to remove the rusty residue/nastiness that is now sitting at the bottom of the sparkplug well? I assume I don't want any of that getting into the cylinder, so that seems tricky.

[sapote]

New question: is there a good way to remove the rusty residue/nastiness that is now sitting at the bottom of the sparkplug well? I assume I don't want any of that getting into the cylinder, so that seems tricky..

Well, I would find a short bolt, or cut one to length, with same threads as the plug and install the bolt with the plug sealing washer. This way you have the well full open to soak and clean up the aluminum corrosion.