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Installed a new top and rain rail on my NA recently- tested today for waterproofness and it leaks on BOTH sides of the car behind the rainrail at each end where the last stud of the centre middle metal rail (not the two smaller outers) go. It seems to have a cutout in the body and this is where the water runs down - is this normal???? I can't imagine it is... Thanks.

Pic might help.

Looks to me like it has been bent out of the way to clear something, possibly a roll bar, If it cant be straightened out, perhaps the void could be filled with silicone . It's a while since I was in there though, anyone else got any suggestions?

I'm pretty sure the thing is factory. Pics online show the same indent both sides.

Maybe there's a crack in the plastic rail?

New rubbery rail.

Yeah, that shaping of the parcel shelf lip rings a bell as factory. However, some NAs do suffer from rusting of the parcel shelf. Might be worth a check of the big forum (Miata.net) to see if anyone has identified why rusting occurs. First though, if you haven't already, clean out the drain holes/pipes behind the seat belt top mount as perhaps the water level is rising in the channel when it rains & overflowing onto the parcel shelf.

Danny wrote:Maybe there's a crack in the plastic rail?

This. Plastic or rubber, they are not indestructible.

Check for blocked drains first, but I'd be psyching myself up to undo the top and physically check the rain rail. I don't know if you can do this without actually removing the roof but I'd look at that first. However removing the roof is not a big deal as it is just lifting off with the frame.

Got the problem close to fixed. The Robbins rainrail has pre-punched holes to rivet the top to. I chose not to rivet the top on and the previous professional installer of the previous roof did the same with the factory rail. I put some silicone over the two holes in the rear (pictured) as these holes don't press up against a surface like most of the other holes do. (the factory 'dent' in the car allows this). Once the silicone set I reassembled and found a couple of other tiny leaks which I will attack in the same way. Pretty easy really,