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M35 VQ25DET rocker cover leak

admS15

By admS15,
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admS15 Grand Master

admS15

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M35 VQ25DET rocker cover leak

 

Hey guys, got an interesting one here. Popped the bonnet the other day as something didn't sound right, could hear a hissing sound like a boost or vacuum leak. Pulled the compressor out and did a boost leak test. Couldn't pinpoint the spot until I put a small hose line into my ear and fished around, turns out the air leak was coming from below a coil pack. Obviously it is coming from the rocker cover seal, the funny thing is that there is no oil passing through, just air, spark plug well was dry as a bone.

 

Has anyone experienced this before?

 

Would this be considered a boost or vacuum leak?

 

Im wondering if in fact it is a shagged seal or maybe the pcv has shit itself and is causing this. As most of us know the seals are non serviceable and new rocker covers are around $300 each. I managed to find a passenger side for 180 brand new but it is the drivers side I require and cheapest I cold find was $318 delivered. I have simply put some 3 bond onto the coil pack seal to try and temporarily seal it up, haven't started it yet, letting it properly cure.

 

Has anyone successfully changed seals of an existing rocker cover. You tube methods look uninspiring, lol.

 

Thoughts and experiences please.

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admS15 Grand Master

admS15

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Nissan quoted me 355. Anyhow, just pulled the rocker cover off and it looks fine, the seals are all intact and in good nick. I'll post pics when I've cleaned it up. Also checked pcv, seems to operate as intended as a one way valve. I'm at a loss to explain why this is happening. Anyone have any other ideas?

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admS15 Grand Master

admS15

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I think I've figured out whats happening. I noticed the bolt securing the coil pack that was leaking was longer than the others. It had penetrated through the cover. I think the air was getting between the threads and leaking out. When I was spraying soapy water it was bubbling at the bolt area. I have put some silicon in the hole now and on the threads of a correctly sized bolt. Will see tomorrow afternoon when I start her up if I am correct. I did also fill the seal up with silicon before I worked out what was happening with the cp bolt. Pictured below.

 

 

 

 

 

 

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admS15 Grand Master

admS15

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Yep, luckily the plastic was still hanging on for its life and didn't fall into the valve train. I saw it while I was cleaning the cover and flicked it off but I didn't click till I was putting it all back together. Old mate I bought this car off had ultra tune do a service and plug change a few months before I bought it. Probably happened then or possibly in japland. Who knows. Hopefully this is what was causing the tiny leak. Will find out tomorrow.

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  • 2 weeks later...
admS15 Grand Master

admS15

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Leak still persists. Im not going to worry about it for now as there is no oil leaking into the spark plug chamber. The car drives perfectly fine and when i did a boost leak test it was taking a long time for the boost to bleed out of the system. I have ordered a new pcv valve in a last ditch effort before i ignore this. Im not totally convinced that it's the rocker cover seal and don't want to buy a new cover and find i still have the same issue. Im wondering if there is something else going on in the background that im missing, is that pressure meant to be inside the engine? Im sure that time will tell all, till then i'll just keep driving.

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Leroy Peterson Grand Master

Leroy Peterson

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I've got a bit of oil on my spark plug on cyl 6 (passenger side), do you have a link to that rocker cover for $180? I've replaced the rocker cover gasket already, which stopped oil weep onto the turbo.

Super strange with that long bolt piercing through...

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admS15 Grand Master

admS15

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I've got a bit of oil on my spark plug on cyl 6 (passenger side), do you have a link to that rocker cover for $180? I've replaced the rocker cover gasket already, which stopped oil weep onto the turbo.
Super strange with that long bolt piercing through...

I'm not at a pc right now but the rocker cover was from amayama uae. Is the vq30det the same though? Shouldn't be hard to find with the part number.

Some bright spark obviously drove that bolt through but it wasn't the source of the air leak in the end. The air is now weeping through the seal around the plug but strangely no oil.
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