Mazda MX-5: Fixing a Leak Under Windshield Wiper Cowling on my NC Miata

Wasn’t planning on working on my car this Sunday… but noticed a two inch wet spot on my new WeatherTech floor mats when I opened the door this morning after heavy rain last night… Dammit!

I knew exactly where the leak came from. Its a common problem discussed extensively on Miata.net forums, and one I should have addressed sooner, but never got around to it. Until today.

There was a day last year, it must have been warm enough because I was driving in shorts and flip flops and felt water droplets on my foot while driving through a sudden downpour. That should have been a sign. It was a similar feeling I experienced while in Thailand driving with the Thai Miata club from Bangkok to the Laos border up north in Tanet’s 2008 Miata…. anyway, I should have addressed this problem sooner but didn’t. The problem lies in a small gasket that separates a plastic clip from the body… it is a clip that holds the windshield wiper cowling in place with a screw on each side of the car… the very left driver’s side and very right on passenger’s side.

You can see the cowling cap in these shots:

The hardest part was taking the cowling caps off… Why?  Because these brittle fuckers crack… and guess what?  I failed!

I used a very thin razor blade and the driver’s side popped out with little effort. The passenger side was a bit harder. I applied a little pressure and it popped out while cracking one of the holding clips.

Fuck!

Anyway, next step was to undo the nuts that hold the wiper arms in place. That was fairly easy. The nut uses a 14mm socket.

Next step was getting the rubber weatherstripping released. There are multiple plastic clips that hold the weatherstrip in place along with the plastic cowling you must remove to get to the problem area.

A little trick with this was using needle nose pliers to squeeze the plastic clips from the bottom and pull them up. The top of the plastic clip is “T” shaped. I found that by gently releasing the rubber to reveal the “T” clip while it was still pushed won so you can turn the “T” 90 degrees, makes it easier to get at them with the pliers from the bottom. Otherwise it’s a bit awkward to get good grip to squeeze and release (to pull up).

Anyway…

This is the problem….

How?

As you can see, the gasket disintegrated… especially on the passenger side… although ironically enough, it’s the driver’s side that leaked on me!

This, apparently is the recommended solution, which of course I didn’t have at home and had to run out to Auto Zone to pick up.

According to the forums, the plastic clip breaks… or is easy to break. So I found it was easiest to put the screw into it, and lift! By lifting up it exposes the area underneath that you want to seal. And then apply the Black RTV. Easy!

I tried to be generous with the RTV, but only time will tell if I see any more water seeping into the cabin.

According to the instructions you have to work quick because the silicone starts hardening quickly, so I tried to expedite the reassembly process.

Finally it was time to test the wipers to see if everything works, and they fall back into correct position when the switch is turned OFF.

They work well!

I really should have done this sooner!

Folks always ask what to look out for/most likely failures when shopping for an NC Miata… stuck open thermostat is #1 issue… I’d definitely classify this as #2. Say no to Rust folks, just say No!

UPDATE March 1: Bought the little cowl grille cap from a local Mazda dealer (shop around because apparently they all have different prices, list price is $3.25+ tax, $3.48 in my case)… online could be cheaper if you have the luxury of time, from $1 on Amayama to $2.20 from Quirk Parts but shipping kills it.

Anyway, had it on the car for a few days including heavy rain storms today and no water visible at all in the cabin. Going to Florida next week where I’m sure I’ll hit more rain, so I’ll continue to update if anything changes.