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Discussion Starter · #1 ·
Hi folks,

I did a search about this, found a few, but neither seem to address what I think is going on, hence the new post.

I have a 2014 Cayman S which is due its 4yr service (car is at 17K miles) which includes replacing the engine air filters. Yesterday, I removed the carpet and plastic trim parts needed to access the filters. I also removed the left-side filter to check it out, and put it back in since the parts will be there in a few more days. I did *not* put all the carpeting and trim pieces back, since I would need to take them off again in a few days.

Today, I drove the car the first time since then, and I noticed a hissing sound coming from back there, inside the car. It sounds very much like air is being sucked in thru a small opening.
I only seem to get it when the car is actually moving, and not if I rev the engine when the car is sitting in neutral. When I am moving, I don't hear it under light gas, but if I press the gas a bit more, it starts making the sound, and the harder I press the gas, the louder/fiercer the hissing sound gets. I had my daughter stick her head as far back as she could back there, and she said it seems to be coming from around where the left-side filter is - the one I removed, and put back on.

The filter was stuck there pretty good, and I had to pull hard to get it out of there. After I put it back in, it seemed much looser in there. I took it out, re-seated it, made sure the filter is pushed in far enough for the notches in the two handles are engaged, tightened the screw, etc. Did this several times, and I am still hearing the sound.

I am suspecting the air is leaking around the filter. I checked both of the green o-rings on the black plastic part that the filter is screwed onto, and I don't see any damage.

The only thing different is, I had wiped the surfaces of the o-rings to clean the dirty grease. There was a generous amount of extra grease around the o-rings, so I used that to relubricate the o-rings before I put the filter back in. The only thing I can think of is, there is not enough grease to seal the o-rings against the mating surfaces. However, I would think that the grease is not viscous enough to seal any opening, and would just be sucked in together with the air. But I may be wrong.

Any ideas what I might try? Should I get new o-rings? Can I be wrong and the sound may be coming from somewhere else completely, and possibly be normal?

Any help would be appreciated.

Berk
 

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Probably just the engine sucking sound thru the filter, since you didn't put the carpet/trim back in place. Like when the round air filter lid was put upside down in the old, carbureted days; intake becomes a lot noisier. I wouldn't worry about it man. Just do the job right when you get the parts, and when you're done, everything should sound normal. It's a job hard to screw up. But next time you want to mess with things like that, take the car for a ride before, so you know how it should sound:). Hey, remember you need to squeeze the filter tabs inward, not just pull out, or you could damage the tabs or something. Good luck.
 

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Discussion Starter · #3 ·
Hi ELP_JC,
Yeah, I probably shoulda driven the car with all the carpeting and trim off, but before I removed the filter! That would have helped answer a lot of questions. As for removing the filter, I knew to watch out for the notches on the pull tabs, etc., so I was able to remove the filter out with no drama, except that it was actually stuck there pretty hard. The issue is, after I cleaned the o-rings, and relubricated them with whatever extra grease I could find around, it seemed much looser to insert it, and take it back out. And unless the hissing sound is for something else (maybe some other part requires a vacuum, or something), I'm pretty certain it is leaking around one of the o-rings - I stuffed a towel over the filter, and the sound got muffled a lot, so it looks very much like it's coming from that filter.

My main concern is, obviously, if there is significant air bypass around the orings, it will a) get unfiltered air into the engine, and b) possibly wear out the part of the o-ring itself (granted, this is probably uklikely).

Is just replacing the filter element, putting plenty of grease around it, and forgetting about it a good idea, or do you think it needs to be addressed?

Berk
 

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Grease on the O-ring makes it slide much easier, but should be equally sealed. I haven't changed my filters yet, but am almost sure they come with replacement O-rings, in case they're damaged. When you get the new ones, if that's the case, problem solved. If not, check the O-ring carefully for damage, AND that it's seated properly. Also the filter surface and where it goes to make sure nothing is damaged, bent, etc. I'd only add a very light coat of oil over the O-ring, just like you do with the oil filter housing. No need for grease IMO. I'll clean all the grease when the time comes, and just do a light oil coat. Don't understand why the factory used Grease. But the bottom line is if the air filter bracket, the housing, and the O-rings are not damaged, and everything is reinstalled correctly, filter should be sealed. But remember even when they are properly sealed, you could still hear the sucking sound without the insulating trim reinstalled. Report back when you get them. Good luck.
 

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Discussion Starter · #5 ·
The grease is translucent, very much like silicone caulk. There was definitely more than a light coating. In one of the write-ups I have seen about replacing the filters, the gentleman there was using a PTFE-based synthetic grease to relubricate the o-rings after cleaning the old grease off.

If putting a bit more grease on/around the o-rings does not stop the leak, I'm thinking of putting something like a rubber band underneath each o-ring so that they stick out ever so slightly more, and hope that will help seal the gap properly. I just hope it won't be too tight when the time comes to replace the filters again!
 

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It's difficult to remove the filters once they've been in place for a bit. Normal. Also normal for them to go in much easier than coming out. Also normal for more engine noise to come through when that think insulating carpet is removed. I have a gutted hatch and it's loud. You're very likely hearing normal noises that are normally attenuated from the carpet.


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