Last year I had my roof replaced and before that the boot always had a little puddle in the jack area. Since the roof replaced and rain rail taped up I still get loads of condensation on the inside of the boot lid. I can not figure out why I get this. I can only think I need a new rain rail or boot seal. Anyone an expert on this problem and wants to have a look to help me?
If you’re sure you dried it out properly and the dampness came back, the other places which sometimes leak are the rear lights: The foam rubber seals behind the light clusters can leak. You can replace the seals or add a bit of silicone. You could also check the drain tube from the filler cap well, and I seem to remember there’s a drain tube from the bottom of the electric aerial too.
we get this too, we too have a new roof but doubt that its the roof at fault, cant leave anything in the boot at all as it ends up soaked through.
condensation under the boot lid is bad, we have wiped it dry a couple of times but its back again the next day, excuse the pun but its putting a dampener on a fantastic car.
 My car had this problem, aftter reading an article “somwhere” i bought some roll on flashing tape the type that has a soft black coating and using a wallpaper roller applied the tape to the bottom of the boot. Since doing this (about 5 years ago) the boot has been ok. I had tried all the usuall remedies,light seals etc, and this was the only thing that stopped it.PS the boot lid was always dripping and the boot carpet was always saturated underneath, but dry on top.
Hi can you please tell me where you got the flashing tape from ? Is it roofing flashing black tape? Would like to try this first before buying new lights.
 Hi, Yes sorry about that,I got the tape from B&Q, but I think most DIY or roofing suppiers would stock it. and yes it is roof flashing tape,Â
It makes good sound deadening too [:)]
If condensation is as bad as you say then water is getting in somewhere. The only way forward is to find out where,which is much easier said than done, I have spent hours tracing leaks in cars over the years you really have to be persistant. On the MX5 have you checked the drain tube from the fuel filler cap recess? Remove the trim and carpet in the boot and check that there is no water ingress from the fuel filler tube connection. A good way of tracing a leak is to sprinkle talcum powder in the likely areas ie around the rear lights,  if water crosses it you should see its path which will then direct you to the cause. Hope this helps.
  Regards Geoff Peace.
There is no way I can find the leak, its so wet on the inside of boot lid and carpet and its raining so much I can never keep it dry. I will have to wait until drier spring weather before I can find the cause of it. I can’t even put the tape on the bottom of the boot because its so wet the tape will not stick even if I try to dry it all off. There is no puddle anywhere. There is no leak from the petrol side. Even if I put talcum powder on I would still have to make sure the boot is completely dry before i apply it. Also please note I do not have a garage so car is outside in all weathers.
 Im glad this has been posted was just about to post the same problem myself. Just cant seem to see where the moisture is coming from really worries me with electrics in the boot etc and causing rust
i have just had the same problem… new rear light seals apear to have done the trick for me
Just received secondhand mk1 rear lights from autolink but noticed my rear drivers side has the foglight on one, these two replacements both have reverse lights - oh no! So that means I have to install a new fog light to the bumper then??
Tried getting the old lights off, they are stuck fast with bolts so my bike spanner and wrench will not get a good hold of them. Will have to wait till after xmas now to sort it with help of garage. Bugger!
I don’t think you need to re fit the foglight to the bumper. You have the one reversing light wired as a foglight so when you replace the rear lights your one for the foglight should have a red bulb in it. Your foglight will still be in the light cluster as it’s the wiring that decides it.
All of my MX5s have experienced condensation in the boot, Mk1, Mk2.5 and Mk3. My view has always been that it’s usually nowt to do with water leaks through lights, aerials or boot seals, although I guess it will occassionally be the answer. One problem is wet items being put in the boot (shopping bags, jackets etc) or a bit of rain maybe getting in when the bootlid is open. The silencer box under the floor then heats the boot space and creates water vapour which condenses on the cold boot skin. The other potential route is water vapour driven out of the cockpit when it heats up, which travels through the rear bulkhead into the boot. Remedies are a little trickier though. Insulate the cold underside of the boot skin, provide some ventilation route for water vapour to escape, if you have, it keep the aircon on? I tried opening the bootlid of my car for a few seconds after journeys to ventilate the boot area, it seemed to help a bit but not exactly scientific!
I had a feeling it was something to do with the exhaust part under the boot. It seemed the logical answer to me. [:D]