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Discussion Starter #1 (Edited)
My e46 has a vacuum leak (I know that for sure) and I've checked and replaced every common vacuum leak source on the car over the past few months. I finally hit a wall and brought it to the mechanic so they could do a smoke test.

They found that the valve cover is cracked near the 6th cylinder (using the smoke test, they didn't find the actual crack visually). I looked around it and found nothing but then pulled the coils out and found that there is a chip out of the socket that the coil goes into on both the 1st and 6th cylinders.

So my question is, do the sockets/holes where the spark plugs and coils go in pull vacuum? It looks like they're separate compartments from the rest of the valve cover so I didn't think so, but it would be too much of a coincidence if not. If it does pull vacuum then I found the source of my vacuum leak and likely need to replace the whole valve cover.

Thanks in advance!

Pictures:
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there is a chip out of the socket that the coil goes into on both the 1st and 6th cylinders.
Someone didn't know how to pull these coils out, and used screwdriver or similar tool to pry the coils causing the chip.

If the crack is deep to the head surface then yes, air could be pulled in where the cover meets the head. Remove the cover to inspect.
 

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My e46 has a vacuum leak (I know that for sure) and I've checked and replaced every common vacuum leak source on the car over the past few months. I finally hit a wall and brought it to the mechanic so they could do a smoke test.

They found that the valve cover is cracked near the 6th cylinder. I looked around it and found nothing but then pulled the coils out and found that there is a chip out of the socket that the coil goes into on both the 1st and 6th cylinders.

So my question is, do the sockets/holes where the spark plugs and coils go in pull vacuum? It looks like they're separate compartments from the rest of the valve cover so I didn't think so, but it would be too much of a coincidence if not. If it does pull vacuum then I found the source of my vacuum leak and likely need to replace the whole valve cover.

Thanks in advance!

Pictures:
View attachment 919180

View attachment 919181

View attachment 919182

View attachment 919183
No. There is a gasket at the bottom of the coil port that can leak but if it did you would no doubt see oil at the bottom of the port surrounding the plug. But up there? No problem at all.
 

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Smoke test, the (by a long margin) fastest way.
 

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My e46 has a vacuum leak (I know that for sure) and I've checked and replaced every common vacuum leak source on the car over the past few months. I finally hit a wall and brought it to the mechanic so they could do a smoke test.

They found that the valve cover is cracked near the 6th cylinder. I looked around it and found nothing but then pulled the coils out and found that there is a chip out of the socket that the coil goes into on both the 1st and 6th cylinders.

So my question is, do the sockets/holes where the spark plugs and coils go in pull vacuum? It looks like they're separate compartments from the rest of the valve cover so I didn't think so, but it would be too much of a coincidence if not. If it does pull vacuum then I found the source of my vacuum leak and likely need to replace the whole valve cover.

Thanks in advance!

Pictures:
View attachment 919180

View attachment 919181

View attachment 919182

View attachment 919183
Could you explain how you "know for sure" that you have a vacuum leak? I assume you can't actually see it otherwise you wouldn't be looking for it. What's you reason for this statement?
 

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Discussion Starter #8
Someone didn't know how to pull these coils out, and used screwdriver or similar tool to pry the coils causing the chip.

If the crack is deep to the head surface then yes, air could be pulled in where the cover meets the head. Remove the cover to inspect.
Tell me about it, I was confused how something like this happens in the first place.

Could you clarify what the head is? Do you mean a crack in the head of the actual engine? Or are you referring to the sockets that have been chipped in the pictures?
 

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No. There is a gasket at the bottom of the coil port that can leak but if it did you would no doubt see oil at the bottom of the port surrounding the plug. But up there? No problem at all.
Interesting... When they did the smoke test at the mechanic shop they said they saw smoke coming from the valve cover next to cylinder 6. That also happens to be where one of the sockets for the coils is chipped. I guess it's just a coincidence and there must be another crack somewhere?
 

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Discussion Starter #10
Could you explain how you "know for sure" that you have a vacuum leak? I assume you can't actually see it otherwise you wouldn't be looking for it. What's you reason for this statement?
Well I've been having some idling issues for a while as well as the codes saying the system is too lean in banks 1 and 2. I brought it to a mechanic a while back and they said the PCV system has a vacuum leak. I repaired that and the problem didn't fully go away. I then realized that there were some other places where vacuum leaks could be happening and I ended up replacing a couple o-rings and vacuum tubes that were worn out and cracked. After each fix, the idling issue gradually go better and better, but like I said I still had the codes and ran out of things to check. I took it to a mechanic yesterday, they did a smoke test and told me that there was a crack in the valve cover.
 

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Could you clarify what the head is? Do you mean a crack in the head of the actual engine? Or are you referring to the sockets that have been chipped in the pictures?
head=cylinder head where the valve cover sits on top. If the cover has cracks deep to where it touches the head then air can leak into the valve chamber then into the intake then lean condition.
Remove all spark plugs then pump smoke into the valve cover port that connected to the CCV (plug up the pipe after disconnected from VC) and see where smoke coming out.
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Tell me about it, I was confused how something like this happens in the first place.

Could you clarify what the head is? Do you mean a crack in the head of the actual engine? Or are you referring to the sockets that have been chipped in the pictures?

The pistons live in the block, the cylinder head goes on the top of the block and holds the valves, but the intake and exhaust tracts are sealed to the outside. The valve cover goes on top of the head, this is what the coils screw on to, and the plugs must pass through to be screwed into the head. From the top -- there is the valve cover that is plastic (some cars have it in steel), then the head that houses the valves themselves, then the block that holds the pistons.

The crankcase is sealed but there is a device that pulls crankcase fumes into the intake so they can be combusted and spit out of the exhaust. Your first two pictures show the same damage to the spark plug well, and the angle does not support the idea that there is a crack. The 3rd and 4th pictures show a more jagged break that could have a crack. I'm not big on the idea that a valve cover can give a Lean condition. but if the crankcase ventilation is blocked and there is enough draw, or if there is a large enough crack that outside air can find it's way to the intake manifold, then you would have a Lean. Your codes would be P0171 & P0174, not likely to be one of the other, it should be both.
 
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