MX5RF 2017 rear window drains and water ingress

Hi All,


This is my 1st post, and sorry if I have not followed any “normal” format. My wife has a late 2017 MX5RF, which suddenly started to smell damp and lots of condensation. IN my wisdom I though I would check water was going down the window drain OK, it was… However was shocked a the large pool of water behind the passenger (left) seat, evdience of mould, dirt etc.


So I started to explore the system and now I am very shocked at the design. Here is the sequence of the water drain.


  1. Its starts with 2 holes in the corner window rubbers (Inner and outer channels) which run into a cup with a flexible small bore pipe.

  2. The small bore pipe couple onto a right angle union joined to a slightly larger short rubber tube, which drains into a plastic plate/trim with a channel

channel panel 1

Channel panel 2

  1. The channel drains into a open reservoir that also collects drains from the door post pillar rubbers. There is a grill in the reservoir (which gets very dirty with mud like material and also has a blockage risk from leaves from the roof compartment). This reservoir overflows onto the roof compartment floor which is a direct path into the passenger compartment traveling under the matting (>1 inch of water in my case)

filter grill

water reservoir 2


  1. The drain goes through the roof compartment floor, via a dogleg join and exits into a compartment behind the seat, in a white pipe with a rubber valve in it (which was stuck in my case).

drain pipe behind seat


location of pipe cubby hole

  1. There is a flexible black tube that collects the water from the white tube and joins onto an orange plastic casting which has another rubber flap in it.

  2. The orange casting exits the compartment through the panel into the space between it, high up, between various chassis parts and brake pipes, (if you shine a torch up you can just see it).

Drain pipe exit


Comment, this is amazingly complicated for something that could have been easily achieved with the rubber tube in (2) going all the way to the exit.


Why are there 2 filters and valves in non serviceable areas? With a single tube the worst that could happen is the rear winder drain floods over the outside of the body work, rather than filling up the passenger compartment. It seems an amazingly stupid design…


The passenger compartment carpet has fibrous pads under it, stuck to plastic sheets (so will never dry), the rear of the compartment allows water to travel to the front, as the cross member is not sealed. From the picture you can see some of the debris that has been washed down.



I have made cone filters to the fit the right angle union in (2), in an attempt to allow this to be more serviceable

cone filter



Request: Has anyone found a way to improve this? Or punched a pipe right through?


Any other thoughts or suggestions?









Looks like an interesting post, but the pics are not showing up…

If you right click on them and open in a new tab they work, I obviously have done some thing wrong with them, not used to inserting pics this way (other forums allow you to directly upload them to the post)


Update, fixed the pictures, they were too big to display, so they are lower resolution now!

Interesting, comprehensive and informative article 're complexities of the roof drain. Forgive me, but the following query kind of ties in with this piece:

Homeward with my new-to-me, Mk3 (see my profile), my enjoyment was limited by the non-roadspeed/engine revs noise emanating from the centre, roughly half-way back. The noise was NOT present on my 2 pre-purchase roadtests. I returned to the supplying garage in Torquay.

The pre-sale service included ‘clearing the roof drainage system… which was completely blocked down to the exit flaps at the bottom’, they said. They were convinced that this new noise was common to Mk 3s (really?) and came from those drain pipes now being cleared. Am I to be deafened by this noise permanently? Surely not!

I would welcome any ideas. Again, sorry to barge in on a previous post but it does seem related.



The exit flaps referred to can get left in an ‘up’ position if the process of cleaning the drains is insert cleaning mechanism (rod, wire, trombone brush) from top and pull back out from top.

Exit flaps in an up position can act as noise amplifiers with the sound resonating back up the tube. The optimal method is to insert from the top (trombone brush is ideal) and pull through from the bottom leaving the flaps in the down position, obviously clear access under the car is required to achieve this.

To the OP, the RF design does seem complicated, will be interested to see what your final outcome is.

Hi Ian H. That’s sooo helpful. I wondered if those flaps might be part of the problem. Together with wheel arch cleaning under the covers, and comprehensive waxoyling throughout, I shall check the flaps… when the weather improves! Mr S

IanH, I would be surprised if you could get a brush of any kind down the RF lower tubes, as it starts with a grill which then has a dog leg in the permanently mounted white connecting tube with slit type internal rubber flap, I only managed to clean it out by sucking water from the top through with it a Vax and taping the right sized tube on it.


Thanks for posting this.  I just washed the car for the second time at the weekend, and have got a puddle in the passenger rear seat well.  Im hoping its just bad washing technique or transit tape stuck over the drain exits.  THE CAR IS ONLY A MONTH OLD FFS!!!  Im a bit confused where the open drain in photo 3 is - under the deck cover below the RF roof?

Close monitoring required over the next few days or a visit to the stealer will ensue.  Even if it’s not blocked this is a massive design fail by Mazda.  I’m reluctant to disassemble a brand new car to investigate.

I know the Spitfire was one of their inspirations for the N.A. but at least it only got wet inside if you left the windows or hood down.  At least until it was more than a month old before the galloping tin worm let the water in from the floor!

Still loving driving my AE30 but slightly concerned…



Hi Will, Photo 3 is a close up of Photo 4, if you 1/2 open the roof and look down on the left side you will see the plastic trim (photo1 and 2) follow the channel down and at the bottom right at the front you will just about be able to see the grill. It’s almost underneath the set belt reel and has a semicircular guard behind it. At month old I would also take it back, they can hardly claim you have failed to keep it clean in a month!!

Good Luck, keep us updated on what Mazda say…


The soft top ND has a different drain system (thankfully) which I don’t think is as convoluted. It does have foam filters to stop leaves and moss etc. blocking the drains and the one-way rubber flap valves. The filter is user serviceable but is an absolute bugger to get to. The standard supplied hardcopy user manual does not mention the filters or the need to check them annually for blockages and cleaning, however the on-line manual does. It may be worth checking the on-line manual for the RF.


The Manual only describes cleaning the window drain outlets and does not mention anything further down.




Is there a filter there, otherwise what is there there that allows debris and leaves to accumulate? 

There is a rubber cup, 2 inlets one from window bottom and the other just between the rubbers, no filter, just a small bore tube. It’s the dirt, dust, grit and tree seeds that accumulate, run down and block the lower filters (I think tree sap may well also stick the rubber flaps shut). Leaves can also blow in when the roof is down into the compartment.

Mazda don’t mention not to buy an MX5 if there is trees, or you park on a dusty road!


Well I’ve done about 250 miles today, mostly in awful hissing rain.  No further ingress seen so I think it may have been steep driveway and/or over enthusiastic cleaning on Sunday.  Anyway I’ll keep a good eye on things and any trouble I’ll be back to the dealer again.  

The main concern is the birch trees on our road, depositing catkins, seed flakes and leaves depending on the season.  At least Eric has given everybody the low down on how to inspect, those photos should go to Mazda Japan with an “Fminus, must try harder” report!

Thanks again



PS on a related note, it seems that if you stop the roof operation mid-way, it throws the sequence 

  • Windows drop 1 inch
  • Roof operation
  • Windows back up 
So that the windows don't close up again.  Easy enough to just press the button to close the windows, just that if you accidentally stop halfway you may not notice the windows are slightly open when you leave the car.  It wasn't till I was fiddling to see inside the works of the roof I realised that I'd wondered why I'd had the odd occasion where I seemed to have left the passenger window slightly open.

I recently bought a Mk 2.5 S-VT Sport & quickly realised that I need to keep an eye on the drains. I found this useful ‘Trombone Cleaner’ which i’m sure all seasoned MX5 experts will already know about, but just incase - here’s the Ebay link :

… came from China, cost £3.44 & seems to do the job perfectly!

Please let me know if I shouldn’t be dragging this through my drains, from top to bottom ( which I tried today and it does easily fit through the pipe )

Cheers, Ian.

Looks very similar to the system on the MK3.5 PRHT which Rodders is helping me with. I’ve just ordered the lower baffle part which looks very similar to the orange fitting in your pictures. I’m guessing that it can only be fitted from inside the car which is a bit of a bugger as it means I’ve got the wrong part !

Did you have to remove the seatbelt tensioners and all the rear plastics to get anywhere near - then break your arm in several places !

Yes the orange fitting is fitted from the inside (bullet point 5) through a panel behind the seat, if you hang upside down and have double jointed left arm you might get it out :wink: (its not that bad but it is a pig it get out and reinstall).

On the RF you can just get to the tray either through from behind the seat or with long tools through the roof hatch, but I could not see a way of taking it out with unbolting and taking the roof off… I’m not that brave!

I have bought a Trombone Cleaner as suggested by Ian which looks like it will help do the job again in the future. I do test it every few weeks by pouring water into the drain and making sure is disappears quickly! If the tray starts to fill then its cleaning time.

Good Luck


Paul had another look at mine today and it seems that the lower valve is in place and the flaps look okay but although the condensation issue has abated, the road noise is a pain to live with. He’s suggested exercising the car while it’s off it’s wheels so we can listen for anything untoward after which I may have to bite the bullet and disassemble the plastic trim behind the passenger seat to see if I dislodged the upper valve.

Unfortunately, the grate on the Mk 3 is very fine and plastic welded in place so a trombone tube won’t help (more importantly, I can’t get a camera down to investigate) but you post and pics have been very helpful though.

Here’s an update on my RF:

In mid November the passenger seatwell filled up again after heavy overnight rain (driver’s side still dry as a bone!).  Needless to say I wasn’t happy and told the dealers so.  They agreed to bring the car in as soon as possible, but as they wanted it for several days to dry out and test it couldn’t be till the first week of December.

In the meantime the carpets generally dried out as it was dry (cold) weather for some days.  But demisting was an issue.  I decided to do a test and poured some water into the two outlets at the corners of the rear window.  On the driver’s side there was the expected gurgle and the same amount of water poured out of the bottom of the car.  But the other side, the gurgling noise was followed by….nothing.  Nada.  Total dryness of road under the car.  Clearly the water was disappearing or being held inside the car.

When the service manager saw this demonstrated it was clear there must be a blockage of some sort, but he noted it was a palaver to get into the rear so hence it would be with them a while, even with that  clue where to look…  3 days later I got the call to collect the car, apparently the multitudinous tubes had not been assembled correctly, it was now sorted and the carpets and passenger seat all out , dried and reinstalled.

A couple of weeks later and we’ve had some really heavy storms, but no further appearance of the water in the seat wells, so it seems like it may have been resolved.  Yes, I did pour water in the window corner when I picked up the car and it did all seem to appear on the road beneath!