no cowl/engine cover + rainwater = ruined 6th cylinder spark plug

Seaneezy

Specialist
Mar 12, 2018
53
#1
It's raining in norcal recently, usually don't have to deal with these sorts of issues.

I was having misfires in cyl 6, somewhat surprised since I replaced the spark plugs less than 2000 miles prior. I assumed it was a leaky injector that wasn't throwing codes but I pulled the plugs anyways to check. Rainwater dripped down my valve cover into my 6th cylinder spark plug guide and rusted out the spark plug. I looked inside the cylinder with an endoscope to make sure there wasn't rust buildup on the piston and it looked fine ( a little caked with oil but I will deal with that later). Considering there was rust all around the spark plug guide and I couldn't clean it well through the valve cover, I removed the valve cover to clean it and replace the valve cover gasket. Cowl would have prevented this, I am probably going to reinstall just the main cowl and keep the BMS cowl filters I have on at the moment. Couldn't find a similar topic on this board so I figured I would post it to help someone in the future.

The spark plug pictured had < 2000 miles.
 

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Sergeant
Free Vendor
Jan 23, 2017
338
#2
If you delete the cowl engine cover should stay if you get a lot of water to prevent something like this. Without engine cover this can also happen with the cowl from our experience.
 

veer90

Lieutenant
Nov 16, 2016
666
West Nyack, NY
#3
Always run the engine cover... it's 3 bolts. I don't understand why people leave it off the mess of wires is so ugly anyways.
 

Torgus

Lieutenant
Nov 6, 2016
696
Boston
#4
Always run the engine cover... it's 3 bolts. I don't understand why people leave it off the mess of wires is so ugly anyways.
Yeah, I just put the front 2 in, it's all you really need imo while running the cowl delete.

Unless you have awd I see no reason to drive a modded N54 in inclement weather. No traction, no point. This is of course if you have another reliable vehicle.
 
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Seaneezy

Specialist
Mar 12, 2018
53
#5
Yeah, I just put the front 2 in, it's all you really need imo while running the cowl delete.

Unless you have awd I see no reason to drive a modded N54 in inclement weather. No traction, no point. This is of course if you have another reliable vehicle.
She gets good traction in the rain unless I'm in boost, but norcal traffic prevents me from even approaching boost when I drive to work in the morning.

Always run the engine cover... it's 3 bolts. I don't understand why people leave it off the mess of wires is so ugly anyways.
I didn't secure one of my fuel line nuts on my valve cover gasket replacement, and I saw fuel spraying in the air when I started her for the first time after reinstall. I'm glad I didn't have the engine cover on then. I really only keep it off when I have to have quick access to my valve cover, i/e diagnosing misfires
 
Jun 4, 2017
843
#6
Yeah, I just put the front 2 in, it's all you really need imo while running the cowl delete.

Unless you have awd I see no reason to drive a modded N54 in inclement weather. No traction, no point. This is of course if you have another reliable vehicle.
I see no point in having an N54 car without also having another reliable vehicle. Lol
 

gmagnus7

New Member
Dec 3, 2018
9
#7
would this be from the lack of cowl, or just engine cover alone? I didn't even know people kept the engine cover off...
 
Jun 4, 2017
843
#8
would this be from the lack of cowl, or just engine cover alone? I didn't even know people kept the engine cover off...
Combo. The oem cowel seals against the hood though. So, you could run without the cover and have no issues so long as you run the factory cowel.
 

matreyia

Lieutenant
Apr 19, 2017
770
#9
It's raining in norcal recently, usually don't have to deal with these sorts of issues.

I was having misfires in cyl 6, somewhat surprised since I replaced the spark plugs less than 2000 miles prior. I assumed it was a leaky injector that wasn't throwing codes but I pulled the plugs anyways to check. Rainwater dripped down my valve cover into my 6th cylinder spark plug guide and rusted out the spark plug. I looked inside the cylinder with an endoscope to make sure there wasn't rust buildup on the piston and it looked fine ( a little caked with oil but I will deal with that later). Considering there was rust all around the spark plug guide and I couldn't clean it well through the valve cover, I removed the valve cover to clean it and replace the valve cover gasket. Cowl would have prevented this, I am probably going to reinstall just the main cowl and keep the BMS cowl filters I have on at the moment. Couldn't find a similar topic on this board so I figured I would post it to help someone in the future.

The spark plug pictured had < 2000 miles.
It is not surprising your plugs are rusted if you did not keep your engine cover on. I have the BMS Cowl filters and cut my cowl to remove some obstruction - looks like the m3 cowl but less pretty. I keep my engine cover on for a few reasons, 1. looks better 2. keeps water from touching sensitive areas on engine 3. muffles the injector noise.

So solution is to run the car with the engine cover protecting those areas...at the very least. Ideally, buy an m3 cowl kit...if money is no object, because let's face it, that m3 cowl retrofit is stupid expensive for what it is.
 
Jun 4, 2017
843
#10
It is not surprising your plugs are rusted if you did not keep your engine cover on. I have the BMS Cowl filters and cut my cowl to remove some obstruction - looks like the m3 cowl but less pretty. I keep my engine cover on for a few reasons, 1. looks better 2. keeps water from touching sensitive areas on engine 3. muffles the injector noise.

So solution is to run the car with the engine cover protecting those areas...at the very least. Ideally, buy an m3 cowl kit...if money is no object, because let's face it, that m3 cowl retrofit is stupid expensive for what it is.
M3 cowel is pretty and provides better sealing than no cowel, but the structure on the non-M hood doesn’t match up with the M cowel to seal it everywhere.
 

Seaneezy

Specialist
Mar 12, 2018
53
#11
It is not surprising your plugs are rusted if you did not keep your engine cover on. I have the BMS Cowl filters and cut my cowl to remove some obstruction - looks like the m3 cowl but less pretty. I keep my engine cover on for a few reasons, 1. looks better 2. keeps water from touching sensitive areas on engine 3. muffles the injector noise.

So solution is to run the car with the engine cover protecting those areas...at the very least. Ideally, buy an m3 cowl kit...if money is no object, because let's face it, that m3 cowl retrofit is stupid expensive for what it is.
M3 cowel is pretty and provides better sealing than no cowel, but the structure on the non-M hood doesn’t match up with the M cowel to seal it everywhere.
The M3 cowl wouldn't have prevented this, it's pretty barren over our engine. I am usually pretty paranoid about the condition of my car, so I prefer hearing injector noise and anything that makes noise under the engine cover to make sure everything is running properly. This isn't an option until we are out of rainy weather so I will just modify my current cowl and leave the cover on.
 

matreyia

Lieutenant
Apr 19, 2017
770
#12
The M3 cowl wouldn't have prevented this, it's pretty barren over our engine. I am usually pretty paranoid about the condition of my car, so I prefer hearing injector noise and anything that makes noise under the engine cover to make sure everything is running properly. This isn't an option until we are out of rainy weather so I will just modify my current cowl and leave the cover on.
It should be the same waterproofing as stock 335i even as it is less coverage. Unless you are saying the top windshield bordering shield is non-existent. I currently run the stock 335i cowl without the microfilter housing and the base cut out completely to m3 shape and proportions...and the cowl broke in half too...but it seems to keep out the rain water from touching anything inside the engine due to the sealing on the edge of the windshield base cover.
 
Jun 4, 2017
843
#13
The engine bay is ONLY sealed from the outside on the windshield side where the support structure of the hood meets the rubber gasket on the coweling that is stock for the car.

The non-M cowel will not seal the bay on an M car, and the M cowel will not seal the bay on a non-M car...unless the front end is swapped so that it is an M hood.
 
Jan 28, 2018
42
#15
Not sure if it is a coincidence, but since I put back my engine cover the car idles smooth as butter after startup every time.
Without the engine cover I had rough idle after startup at least once per week.

So not installing the engine cover because you are planning to check your spark plugs to investigate rough idle might be not be the best idea...
 

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