I don't have a good solution to this problem, but the solution published by mybunkey is incorrect. The problem has nothing to do with the air conditioning. The MX-5 has a couple of small pans located behind the seats under the area where the top folds. These pans catch water that runs off the roof and leaks into the passenger compartment where the roof joins the car. From these pans there is a hose that allows the water to drain through openings in the rear tire-wells. Unfortunately, not only water finds its way into the drains, but so do leaves, twigs, bugs and who know what else. Eventually the drains get clogged and the pan overflows right into the floorboard. It only took 6 months for this to happen to my 2007 in Houston. The dealer cleaned out the drains and replace the carpet, but his only suggestion for prevention was to not park outside! The REAL problem, however, is the drains are completely inaccessible - there is no good way to get to them to unclog them! An internet search will find several ideas about what and how to snake a piece of wire or something into the drains, but I’ve been completely unsuccessful. It’s raining her today, my floors are wet and my care smells moldy. This is my 3rd convertible and it’s the only one to have this has happened. It’s an inexcusable design flaw and frankly it’s enough to make me think of getting rid of the car.
adh79 you are right on for most of your analysis, but the answer is not complete. Here are 10 steps to solving the problem and making sure it won't happen again.
1. When you change oil or find a wet floor, right or left, with the top down pour a quart of clean water in each side of the convertible well. Water should drain vigorously from each side just in front of the rear wheel. If not, your convertible drains are plugged or partially clogged. It seems the right side clogs more than the left. If it is clogged or plugged here is what to do. And, it is accessible, just not from the top which would be best.
2. Get a 2 foot piece of 1/4 inch plastic hose that is fairly rigid. I use a piece of garden drip hose (available for Ace, Lowes or Home Depot). It has to be fairly firm, but not rigid.
3. Block the front wheels. Jack up the MX-5 at proper jacking points. Put jack stands under the car. Lift it about 12 inches off the ground so you can see the white plastic drain fitting just forward of the rear wheels on the body. Most of the time it will be slightly wet if the drains are completely plugged.
4. Insert the hose into the white fitting. Wiggle and twist until you have about 3 inches left in your hand. You will probably get some water draining when the hose is half way inserted. The rest of the hose will hopefully stir things up when you twist the hose during the cleaning process.
5. Place a old towel or piece of cloth on the ground under the fitting so you can see the sediment coming out as you clean the drain. Move the cloth to a clean portion each time it needs to be moved.
6. Pour 1 quart of water into the side you are trying to unclog. You will note that there is sediment on your cloth. If someone else is available have them pour the water in as you twist the hose.
7. Repeat the process until the water doesn't deposit any sediment on the cloth. That may be 5 or 6 times.
8. If one side is clogged and the other isn't, I would clean it anyway.
9. Check and dry the floor area thoroughly otherwise it will rust and mildew.
10. Store the little piece of hose in your trunk for future use. Just remember to add this test to your preventative maintenance schedule. Do it when you change oil.
For some reason, the answer I had given was not related in any way shape or form to a mazda. I was answering a question someone had asked about a Nissan. How I ended up on a Mazda page is a mystery to me.
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You shouldn't do this from underneath as the posters suggest.
The 'flap' is a one-way valve, and is fitted to reduce road noise transmission to the passenger compartment. If you force a tube from below you are likely to damage the flap (though the small screwdriver method may work if dome correctly).
I use a flexible net curtain rail (the bendy white things) with a test tube cleaning brush fitted to the end. Some from miata.net use a trombone cleaner (basically the same thing, a flexible rod with a small brush on the end).
Either way, it should be pushed from the top down, then pulled out the bottom. This way you're pushing the flap in the direction it's designed to work in. If you push from below you risk damaging the flap, and it introduces a HUGE amount of road noise to the cabin.
Rmayer807 is exactly right with his very excellent 10 steps, except there is one small, but important detail that was left out. At the beginning of step 4 you should note that before you can fit the hose into the white fitting, you must first lift the black rubber flap that is just inside the white fitting. This can be done with a very small flat head screwdriver (like the ones found in an electronics repair kit). I fiddled around for about 10 minutes trying to get the hose to go in further than two inches through the space at the inside top of the white fitting before I realized that the black rubber piece in the back wall of the white fitting was not a plug but a flap that is evidently there to prevent water being sprayed up into the drainage system from off of the road. At least this is true on my 2006 Miata MX-5 Convertible, which was having the same problem of water leakage inside the driver's compartment.
Thanks a lot rmayer807 for the very detailed and accurate fix for this problem. Hopefully my little extra info will save some other "not very mechanical" person some time and frustration!
Some additional info: My previous post was made after clearing the driver's side drain and the info provided is correct for it. Showing my less than mechanical aptitude I had assumed that the passenger side drain would be exactly the same; never assume. Although the basic set-up was similar with the white drain fitting there were two major differences. The first was that there was some sort of box (probably electrical junction) attached to the under-carriage directly in front of the white fitting which made entry to the fitting very difficult. Second, the rubber flap was not in the back wall of the fitting, but instead was located at the very top of the fitting which, combined with the intruding box, made it impossible to pull the flap back with a screwdriver as I had on the driver's side. I worked and worked until I was able to basically force a tube past the flap, but was never able to get the tube to go very far.
After about 30 minutes I decided to take a different approach. I fired up my air compressor and put my blower tube on the air hose. This blower tube has a 1/16 tube about four inches long with a 45 degree bend about halfway down. I first tried forcing air into the Miata's drain system from the top, but this didn't work well since there are so many vent holes along the top of the system that it didn't give good compression. I finally decided to get back under the car and try blowing air up through the white drain fitting. Before I did, i wadded a bath towel over the top drain tray to prevent dirty water from possibly spraying out of the top of the tray and all over the vehicle. When I got under the vehicle It was a very tight fit getting my air blower into the white drain fitting, but thanks to the angle on the end of the blower tube I was able to get the nozzle past the rubber flap. One blast of air was all it took and the clog was broken up and a lot of dirty water gushed out of the tube. Next time I clean the drain system I will probably just use the air compressor since it is a lot faster.
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Xmascarol107: It appears that what the dealer has found is a problem with debris collecting at the A/C eveporartor drain hole. In terms of answering your question: Yes, it will cause the floor to rust out if you do not allow it to dry out. You must also get the carpet and jute (the carpet insulation) dried out, or you will have a mildew problem as well. You can more than likely clear the passageway for the A/C condansate drain your self. The drains are small rubber tubes which come out of the firewall or tunnel on the passengers side close to the foot well. Some will have the appearance of the end being flattened. If you get a small wire or probe you can work into end of the hose, as soon as the debris is dislodged, the water will start to drain. You will have to use a little common sense in terms of clearing the drain, but it is not much different than cleaning any other type of drain.
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