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Discussion Starter · #1 ·

I have Subaru Legacy 2013.
At some point I started to smell in cabin. It was resembling exhaust. Smell was coming sporadically. Presence was dependent on outside temperature I think and was hard to reproduce reliably. I went to the dealer they checked what they could and found nothing bad in engine. Also, smell was hard to reproduce. I got into this situation of not being able to reproduce for dealer couple of times and gave up coming to the dealer.

Replace sealer between air intake and engine compartment cover
Re-seal air intake bottom where it attaches to the car body
Before you do two items above, make sure you do not have other possible reasons: oil leaking, PCV not working, something damaged and so on. There are plenty of other possible reasons. Search for them or ask mechanic to check the car.

I tried to clean AC. Did not help or seemed helped slightly. I did more thorough cleaning with removing of blower. Strangely, blower and it’s compartment was pretty dirty. Dusty and dust was black. Like diesel exhaust. I cleaned it up. Things eased slightly but did not really become fixed.
Smell was also varying in kind. It was like exhaust, then like oil, or burning resin.
I realized that I had oil stains in area around oil cap and filter, so I cleaned all of it with paper towels, washed engine with water. After this oil part of smell decreased significantly (although did not fully disappear). However, resin part remained and also, there is some plasticy smell in engine compartment as well, which I think is natural. I found in one of forums and resin smell likely comes from exhaust pipes being pretty close to CV boots that are covered with resin and It seems it’s right explanation for the strong resin smell. Another possibility is resin piping that becomes hot for other reasons. I think those smells are legit. They just shall not get into cabin.

I realized that air from engine compartment somehow gets into cabin.
I started to check what isolates air intake parts from engine compartment.
First I replaced rubber sealer between air intake and engine cover.
It was slightly deformed (like 1-2mm) at the top, but it was enough for not serving its function well enough. I just went to the dealer and asked to buy it and they sold it to me. It was cheap.
After installation of new sealing rubber smell halved. See picture for the part. Sometimes smell even was disappeared completely, but depending of temperatures and wind direction was still appearing and was becoming very strong in some cases. Strangely, but how it behaved also was dependent on wind direction. When wind is from right to the left, the smell is maximized, in opposite direction it was noticeably smaller.
So, I was investigating further. I recalled, that I had windshield wipers motor replacement because of recall by Subaru.
Next thing that I thought of was sealer beneath air intake. I asked to buy it as a part from dealer, but they told it is not separate part and is not sold as such.
So, I ordered some sticky foam stripes like 10x3mm of different density and decided to remove air intake and check the sealing there and restore it.

When I removed air intake cover. I realized that when windshield motor was replaced on recall, the sealer was broken and was not put back properly and that was pretty likely reason of the issue. Basically, proper sealing was neglected by dealer.
So, I removed wipers and removed air intake plastic part. Removing plastic was not easy. It has fastening that are not easy to understand how to detach. I mean “unscrew” those plastic bolts that are fasted in their ends. I used two screwdrivers. With one I was leveraging the top of the “bolt” so that it could go up if released and with second I was trying to release it by stretching the wafer that was holding it. Bolt is kind of trapped in the wafer. So, wafer shall be “unlocked” to release the bolt. This was a bit of a pain and plenty of time for release the first one. However, when you realize how it works, it goes easier, although not completely easy. Eventually, I removed the part. I cleaned everything inside and below air intake. I put foam around cables that come into holes of air intake. I foamed around sprinkler piping. (See pics how wrong they were). I added foam in places where I was suspecting thing can be not sealed well. My 10x3 foam stripes I applied as is or I was making strips of 5x3 or 5x6 or 10x6, depending on the need in place of application. ( I cut it with scissors or was sticking stripe to itself.) In the end I also, attached some foam to car body under sides of air intake part as I understood plastic can go pretty far from body there. All in all I made sure I maximize proper sealing. When I put cover back and run the engine for some time I realize that it was it. Smell went away completely. What I was surprised that delar did not mention this and serving manager was assuring me there is no any gasket or sealer there. I afraid manager is not mechanic or they are not interested in fixing such issues. Then cars get to them faster via trade-in.
On foam choice. I ordered 3 kinds of it and selected the one that is not too dense and not too soft, but something in the middle. Hope this will be useful.

Interesting thing I found that in places engine air goes out at sides of air intake it is pretty close to intake itself and I was long time thinking it gets into cabin through there. I think it is possible depending on wind, but my real reasons were not there. They were inside a car because of broken sealing.

On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
27,163 Posts

I have Subaru Legacy 2013.
nipped your post off that "OLD" thread about old cars.

and started a new one.

glad you got a fix, hope it stays that way.:smile2:

3 Posts
Discussion Starter · #3 ·

Thank you.

I have extra comment on how it went for me.
After I re-sealed. Things went well for 2-3 weeks, but later smell started to appear again.
I suspected that vibration weakened seal around cable entry (from engine compartment into air intake compartment).
I was searching how to seal it best and found this sealer: "Flex Shot Rubber Sealant".
What is good about it that it remains soft when dried and its adhesion is not too weak nor too strong.
So, just in case it can be removed relatively easily.
I applied it once around cable and also around pipe for windshield liquid. Things got much better.
For cable I had to do another round. After that my car become like new. I do not have any issue with this
engine smell anymore.

I think in general, if somebody has this kind of smell issue, "Flex Shot Rubber Sealant" seems like a good option
to try first. One do not need to remove air intake cover (which is a bit difficult process) to try it.
Just try to seal places that could have been compromised if cover was ever removed.
For most cases I think it will be enough. At least it is worth to try it first I think.
I think this sealant can be used to seal all air intake around, but I did not really need that.
For my case I needed to apply it in couple of places and it was enough. It works perfectly.
Wanted to share this, because, I think this issue is pretty common and I did not find good solutions for it anywhere.
Also, official service was not helpful, they could not detect reason as this thing is a bit sporadic and
reproducible after 20min+ drive and depends on wind direction.
Although good mechanics I can imagine might know how to fix this.
Hope this will be useful for other folks.

3 Posts
Discussion Starter · #4 ·
I have one more update here.
Steps above mostly got a fix for me. However, from time to time I was getting smell, which was depending on wind direction and I was guessing where it could came from.
I was checking different stuff and eventually I realized the fact that air from engine compartment blows on top of doors rubber sealing (to blow out water from rain and snow I guess) and if door sealing has any glitch, that engine compartment air starts syphoning into the cabin.

So, if your cabin gets smell from engine compartment, check how well your doors are sealed. Especially front, as they are hit with engine compartment air first.

First thing one might want to do is just clean the sealing fitting surfaces of car body frame and sealing rubber on the door.

In my case, I also found there was a not accurately done silicon sealing of door hinges mounts.
Silicon sealer remains/drops were stick to surfaces were door sealing rubber was fitting to body frame around door.
So, fit of door rubber sealing was not perfect and wrong air was very slowly getting into the cabin.

Once I removed remains of silicon sealer and cleaned door sealing rubber and fitting surfaces of car body around door, my car got no engine related smells in cabin. At all. Period. I drive it more than 6 months since then and got not issues on that front. At all.
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