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Discussion Starter · #1 · (Edited)
Hopefully I haven't missed an existing thread on this issue; I looked around a bit.

For years my 91 LX has had a slow leak into the trunk wells when it rains. For a long time this was thought to be from the sunroof, but it's currently sealed up with a bead of silicone on the exterior. It doesn't really open or close anyway, presumably on account of being a 30 year old mechanism that sat outside for a decade, but I haven't really looked very far into that yet. When not siliconed, the closed sunroof seems to leak a little into the area up there between it and the interior slide. Probably needs a new seal. Anyway, rain and hose testing reveals that water is still getting into the trunk. While I did find water in the spare tire well, this was before messing around with stuff and resealing the sunroof and it hasn't happen since (yet?). The main issue is that water is entering the side wells where the jack etc. are kept. The source of the leak appears to be the exterior vents(?) of some sort that are found on either side of the rear window. I don't have a picture on hand of this but I can post one later if anyone needs a visual. The water appears to be entering through those vertical-ish openings and pooling inside the bottoms (of course they have a pocket at the bottom with nowhere to drain out), where it then slowly drips through a pinhole back inside the body and runs down into the side wells.

My question, in the interest of stopping the rust invasion, is this: has anyone had this problem and know what to do about it, and does anyone know what the purpose of these rear-facing exterior vents are that keep letting water into my trunk? I have yet to find anywhere they lead.

Edit: I forgot to mention that the taillights were also part of the leak but have been sealed with silicone. The only remaining leak source I'm aware of is the drains/vents.
 

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Have seen this a couple of times when working(As a Mazda tech, and independent) I have seen two possibilities that happened more than once. Because of the deep channel running from after the bottom of back glass all around the trunk lid perimeter, a large quantity of water can be funneled to the taillight lens seals, and seep in from there. On the older models parked where leaf and needle debris can build up, the pinch weld that the trunk gasket attaches to will rust inside the gasket, and provide a water path into the trunk. Since you mentioned sunroof, the same leaf debris would clog the four corner drains of the sunroof, especially when car is parked on a slope, and allow water into the cabin as well through its frame channel overflow.
 

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It happens a lot to these cars. I had a 90 626 that did it bad. I replaced the seals for the tail lights and that did not help. As far at the sunroof, it has drains at all four corners, so unless its clogged you should not get any leak from it. You can test it by opening th e sunroof and pouring water into the channels. You will see water hit the ground very quickly.
My 89 Mx-6 does it a little so I have not got around to fixing it. When I was researching technical service bulletins. I came across bulletin about leaking trunks. And its the large trunk lid seal. I wish I could find it again. But it basically said. Pulling up the seal and applying sealant to certain areas of the metal. I believe it was at certain seams.
If anyone has access to these bulletins I am sure we can find it.
 

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It happens a lot to these cars. I had a 90 626 that did it bad. I replaced the seals for the tail lights and that did not help. As far at the sunroof, it has drains at all four corners, so unless its clogged you should not get any leak from it. You can test it by opening th e sunroof and pouring water into the channels. You will see water hit the ground very quickly.
My 89 Mx-6 does it a little so I have not got around to fixing it. When I was researching technical service bulletins. I came across bulletin about leaking trunks. And its the large trunk lid seal. I wish I could find it again. But it basically said. Pulling up the seal and applying sealant to certain areas of the metal, then pushing the seal back into place. I believe it was at certain seams.
If anyone has access to these bulletins I am sure we can find it.
 

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1991 MX6 LX
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Discussion Starter · #5 ·
Have seen this a couple of times when working(As a Mazda tech, and independent) I have seen two possibilities that happened more than once. Because of the deep channel running from after the bottom of back glass all around the trunk lid perimeter, a large quantity of water can be funneled to the taillight lens seals, and seep in from there. On the older models parked where leaf and needle debris can build up, the pinch weld that the trunk gasket attaches to will rust inside the gasket, and provide a water path into the trunk. Since you mentioned sunroof, the same leaf debris would clog the four corner drains of the sunroof, especially when car is parked on a slope, and allow water into the cabin as well through its frame channel overflow.
I edited my original post to reflect that I did indeed seal up the taillights which used to leak. Totally slipped my mind. The main trunk seal held up great when I hose tested it.

To clarify this is what I'm referring to. It seems they're the sunroof drains? They have space inside below the bottom hole where water collects and then finds its way inside the frame.
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I don't wash my old Mazda(s) a lot, but when I do I make sure to spray the circled vent areas and especially the area below that where the body curve meets trim--I'm shocked at times on how much garbage (leaves, twigs and just general dirt) comes out. Another thing to consider under the truck lid is the round black body plugs at the top. They tend deteriorate over time (and get smashed by the lid) and will leak. All I can add is to do a water test starting with sunroof and work your way back to the truck and hopefully you'll find your leak(s).
 

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On my GT it seems to seep in after a hard rain through the fasteners on the rear spoiler...best I can tell. It ends up in the right side of the trunk but up away from the taillight...and I have a rusty fastner from the spoiler.
 

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Hopefully I haven't missed an existing thread on this issue; I looked around a bit.

For years my 91 LX has had a slow leak into the trunk wells when it rains. For a long time this was thought to be from the sunroof, but it's currently sealed up with a bead of silicone on the exterior. It doesn't really open or close anyway, presumably on account of being a 30 year old mechanism that sat outside for a decade, but I haven't really looked very far into that yet. When not siliconed, the closed sunroof seems to leak a little into the area up there between it and the interior slide. Probably needs a new seal. Anyway, rain and hose testing reveals that water is still getting into the trunk. While I did find water in the spare tire well, this was before messing around with stuff and resealing the sunroof and it hasn't happen since (yet?). The main issue is that water is entering the side wells where the jack etc. are kept. The source of the leak appears to be the exterior vents(?) of some sort that are found on either side of the rear window. I don't have a picture on hand of this but I can post one later if anyone needs a visual. The water appears to be entering through those vertical-ish openings and pooling inside the bottoms (of course they have a pocket at the bottom with nowhere to drain out), where it then slowly drips through a pinhole back inside the body and runs down into the side wells.

My question, in the interest of stopping the rust invasion, is this: has anyone had this problem and know what to do about it, and does anyone know what the purpose of these rear-facing exterior vents are that keep letting water into my trunk? I have yet to find anywhere they lead.

Edit: I forgot to mention that the taillights were also part of the leak but have been sealed with silicone. The only remaining leak source I'm aware of is the drains/vents.
Mine just started doing this about 2 months ago, never before. It's only one side for me, the drivers side trunk pocket. I inspected everything and noticed my trunk latch mechanism was not allowing the truck to go down enough and thought this was the likely culprit so I adjusted it and the trunk was now sitting level with the quarter panels. I waited till the next heavy rainfall and checks and there was still some coming in, it was very little compared to before the adjustment i made. I decided to wait for another heavy downpour and this time a little more came in as the rainfall was heavier and lasted longer than the prior rainfall. So though it is less, that didn't fully stop the water entry. but it was like night and day difference. Prior to the adjustment the whole pocket was full, now it was like a small layer and only on the side of the slope.

Like you, I also considered the vent next to the rear glass but haven't done any investigation as yet.

I saw someone mention one of the other things that I am thinking might also be contributing to it, the circular rubber plug/seals just above each tail light. Mine are there but not tight and kinda just sit in the hold and if you press on them after a rainfall you see the water escape the edges, and the edges are jagged from age so this might be one likely possibility. It's winter here so won't work on that till the spring, but I plant to replace the grommets or seal the with silicone and see if that solves it.

For me when it was the tail lights, the spare tire basin would also fill in addition to the side pockets, I used electric tape on my taillights as a temporary measure to see if it was that and it was the solution for most of the water issue, bit as I said the one side pocket is a new thing and only started recently.

I'm also wonder if the trunk seal can do this
 
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