Foam dab on MAF sensor - and lack of self control

[rationull]

This morning, when I went out to check my oil I noticed a small white dab on top of the (hitachi, if it matters) MAF/Intake air temp sensor in my 07 civic. I hadn't noticed it before and it looked like an insect egg sack. The sensible voice in my head said "That's odd, go check some online photos of civic engine bays and see if it's normal". The other voice said "That's not normal, you would've noticed before."

So, I scraped it off with a little pick. During scraping I noted it wasn't in fact and insect egg sack but some kind of rubber or foam. It looks like there might be two very small holes under it but it's hard to tell because I didn't clean off all the foam/rubber. Of course after I scraped it off I checked some pictures and noted that they all seem to have this.

So now I'm wondering what it's for and if I shouldn't have scraped it off. I thought it could be insulation for the intake air temp sensor but on my drive to work today the intake air temp behaved normally (monitoring it on an SG2).

Anyone have any idea what purpose this serves? Do I need to do something about this (besides behaving differently next time )?

 

[Seijirou]

Can you take a picture?

 

[rationull]

Not now, but I should be able to take a high res one tonight.

 

[mechtech2]

If it's on the outside, it's probably added insulation against water/dirt/etc. where the wiring connects.

 

[rationull]

It is (was) on the outside top. It's possible it's insulation but it's not really near the plug. The rest of the top of the unit is solid plastic so there's gotta be a reason for an opening there if there is one.

 

[tom slick]

The factory will often put a mark on something that is an adjustment or that needs a specific torque to make sure that nobody else messes with it. it is very similar to what you describe, or maybe a thick paint or bird poop.

www.flightinnovations.com/images/wings/061022.jpg

 

[rationull]

The "bird poop" descriptor is pretty close

I was thinking it could be an adjustment screw or something, but it doesn't look like it. Here are a couple of pictures. In the zoomed out picture, we're looking at the circle in the lower left of the panel labeled "Hitachi".

As you can see there's an indentation with a raised "dome" inside it. The dome has smooth sides, and around its edge (the bottom of the indentation) seems to be solid plastic. I didn't try pushing it in or anything but it doesn't seem to be any kind of adjustment apparatus to me. The whole thing was covered with this white rubber/foam stuff.

I should've just left well enough alone this morning but now I'm curious. It's got to serve some purpose (else why would they have covered it?) but it doesn't appear to be open to the inside of the sensor at all.

I took the sensor out, and the "feature" is situated above the main part of the unit that holds both the hot wire for the MAF and the thermistor for intake air temp (the block that extends out into the intake tube).

 

[AcuraTech]

Wow, that's an esoteric question. I don't think many people outside of the factory would have that answer. It looks to me like a dab of white lithium grease. But who knows.

 

[Eddie]

I think you broke it now!!

 

[rationull]

Hah, yeah I know it's esoteric (and I don't think it's broken) but I was just curious. It does look like lithium grease in the pictures, but it's definitely not. It's much harder than that.

I doubt it's specific to this car since it's on such a generally used part.

 

[-Clayton-]

My uneducated guess would be that it is from the molding process and that stuff on there is to keep the moisture out.

 

[AcuraTech]

Originally Posted By: -Clayton-
My uneducated guess would be that it is from the molding process and that stuff on there is to keep the moisture out.


Yep. That would be my guess too. Doesn't look like it'll hurt anything now that it's gone, but if your MAF sensor goes out, let us know!

 

[mechtech2]

Obviously there is something other than a plain flat surface under the substance.
I'd seal it with a dab of RTV.
Can you take a peek at any other cars like yours under the hood?

 

[rationull]

I hadn't thought about the molding process, but I guess that makes sense. I will seal it with something (and will update if the sensor fails!).

mechtech: There's a small raised "nub" under the stuff, with flat solid plastic in a ring around it. The nub is smooth plastic. It's possible that it is a molding seam and the ring and the nub are parts of different plastic pieces (I think that's the explanation that makes the most sense right now).

As far as other cars, Bulli's picture of his 07 civic engine compartment here: Post pictures of your car's engine compartment

shows the dab fairly clearly, so I know it's on other cars. (The MAF sensor is on top of the air box just to the left of the brake fluid reservoir). The dab is the speck of white among all that black plastic.

 

[Westerly]

I agree that the foam boning agent was there to seal the moulding mark left behind from the manufacturing process. I would DEFINITELY reseal that with heavy duty RTV sealer. If left exposed it could let moisture in.

 

[mechtech2]

It also could be a tell sign for 'anti tampering'.

 

[oilyriser]

It's probably a tiny calibration adjustment knob that's set at the factory.

 

[rationull]

It could be an anti-tampering thing but I'm not sure why they'd do that. I don't think it's an adjustment knob since there's nothing to grab on to (it's smooth all around) so I'm not sure what kind of tampering it'd be detecting.

At any rate I put a healthy helping of clear RTV adhesive/sealant over it so no moisture should be getting in.

 

[steve20]

you could always take the same approach as Honda: if there is no CEL there is no problem