Battery vent tube - how to vent out of car?

[KevinC]

I had to replace my 14-month-old Duracell AGM battery over the weekend. The original battery was still in the car - 10+ years - when I bought it in late 2018. I decided to proactively replace it. But the new one crapped out under warranty already.

When I replaced it the first time, I reconnected the battery vent tube, but when I pulled it out of the bad battery this time, I looked down and the other end is just flopping around inside the car - not actually vented outside the car at all. I couldn't find any elbow or other piece lying around down there to connect to a hole that's nearby, which I ASSume is where it should properly vent to.

Is that in fact a correct assumption? If so does anyone have a part number (or 3rd party source) for such an elbow or other piece to connect it? realoem is down at the moment so I wasn't able to look there. Thanks for any pointers.

[KevinC]

OK, some further digging more or less answered my question - there's a vent hole there someplace, that *should* have a rubber grommet in it. I could find the grommet when I was in there, but I did see a hole. I ordered a replacement grommet as part of a vent tube kit from Amazon for < $4 that arrives tomorrow. I'll get back in there and vent the sucker properly.

[vt100]

Now I'm anxious to check mine...

[XMetal]

Originally Posted by KevinC

OK, some further digging more or less answered my question - there's a vent hole there someplace, that *should* have a rubber grommet in it. I could find the grommet when I was in there, but I did see a hole. I ordered a replacement grommet as part of a vent tube kit from Amazon for < $4 that arrives tomorrow. I'll get back in there and vent the sucker properly.

Please post a picture of that grommet and vent tube connection when you are refitting it? Very much appreciated.

[Efthreeoh]

On the E86 the vent tube hole is on the left side short wall of the battery box about 3 inches forward of the back wall. I'll snap a pic later today.

[Sergio19]

Doesn't show where the grommet is installed but here are the part numbers (#5-7):

https://www.realoem.com/bmw/enUS/sho...diagId=61_1613

[XMetal]

Originally Posted by Efthreeoh

On the E86 the vent tube hole is on the left side short wall of the battery box about 3 inches forward of the back wall. I'll snap a pic later today.

Not for the M Coupe - it's buried somewhere under the battery tray behind the passenger side bulkhead.

[Efthreeoh]

Originally Posted by XMetal

Not for the M Coupe - it's buried somewhere under the battery tray behind the passenger side bulkhead.

Why would the MCoupe be different than the 3.0si Coupe? The trunk floor pan is the same part number for both cars as is the vent tube parts.

I took a pic. The vent tube inserts into the left side of the battery box just aft of the junction box, about 6 inches in front of the back wall of the battery box.

I don't know how to attach a pic using my phone.

[XMetal]

Originally Posted by Efthreeoh

Why would the MCoupe be different than the 3.0si Coupe? The trunk floor pan is the same part number for both cars as is the vent tube parts.

I took a pic. The vent tube inserts into the left side of the battery box just aft of the junction box, about 6 inches in front of the back wall of the battery box.

I don't know how to attach a pic using my phone.

The MCoupe battery is not in the trunk floor pan - Look at the attached picture.

[Efthreeoh]

Originally Posted by XMetal

The MCoupe battery is not in the trunk floor pan - Look at the attached picture.

Got it. I guess the MCoupe muffler takes the space of the regular Coupe battery box. I've never seen inside the trunk of the MCoupe, I figured the battery was in the same place for both versions.

[KevinC]

Well, finally tore in there today and vented the mf'er properly. What I found was kinda interesting.

Here's where the only hole is that could be used to vent it that I could find anywhere, so I ASSume this is it..



To be prepared before I pulled it all apart again, I ordered this Dorman vent tube kit from Amazon, for a whopping $3.66 delivered..



So I find the tube dangling where I left it, but no way to shove it into that tiny hole. Looking at the tube, it was clear that it had been shoved into one of those L-connectors at both ends - meaning that it was venting out of the car through one as well as connecting to the battery the same way. The tube was BARELY long enough to MAYBE connect from the battery to the hole, and very awkward to reach around down there, so I cut a slightly longer length of tubing from my now very handy kit, and shoved the included 2nd L-connector into the exit end, then maneuvered it into the hole. It was a bit loose in there, so I secured it with some electrical tape. I also didn't have a plug for the vent on the other side of the battery, so I covered it up with a couple of pieces of electrical tape, that should do the job. Voila, now properly vented, and I'll sleep better when the Battery Tender is connected. I ASSume that's how I killed my last battery in 15 months - I was letting the car sit for 1-2 weeks at a time, without being on a Tender, and letting it discharge that much isn't good for the battery, particularly for AGM batteries apparently. I have no idea what happened to the other L-connector; apparently it must have slid underneath the tray and vanished.

[Molez93]

^This matches the situation I recall when replacing my OE battery ~6 years ago.
Short tube, barely reaching the vent hole? Check.
What am I supposed to do with that unvented hole in the battery's other side? Tape it...check.

Mine sits for 5-10 days consistently during the summer without any tender. Got 7 years from the original one and 6+ years on the current/2nd one. It's only on a tender every week or so for 1-2 days during winter storage.

[KevinC]

5-10 days is apparently ok in your situation/your battery. I was pushing beyond that. Live and learn. Easy enough to keep it hooked up when I park it.