from what ive heard, the intercooler on these cars are a bit of a poor do, as i found out within a few weeks of buying my car. so instead of forking out however many £'s on a new or used one, i set about finding a way of repairing it without removing it.
on mine, i had three cracks in total. two on the top, and one on the bottom. i first saw the two on the top after i noticed oil on the drive way and quickly fixed this, but i didnt discover the one on the bottom until a few week after the top because of the poor attempt mazda did on preventing the problem using silicone.
heres what i did (on the bottom)
wheel off, wheel arch liner out and clean all the residual oil off the liner (there was a bit)
clean off all the silicone, and use light emery cloth to clean the area up. suddenly the crack becomes very obvious.
just to check, i started the car and reved the engine to build up pressure in the intercooler and force the oil out.
only a drop, but quite a lot considering it was only 10 seconds of reving.
so again, emery clothed and cleaned with de-greaser. then, i removed a little bit of the metal, to make the hole bigger so the compound im using can stick better, and so i remove as much oil as i can from the crack.
so this is what i used. its a two part metal mix, like epoxy resin but designed for metal. easy to use and apply, and reasonably cheap (unless work stocks it, then its free...) there are a few variations to this, such as belzona, but the loctite stuff is cheaper and works nearly as well.
and heres the finished result
it can be made neater once hardened, but you arent going to see it so im leaving it as it is. the top has been there for two weeks now, and not a drop has come out, so this should perform in the same way.
so all in all, a much cheaper and easier way of repairing the intercooler. id be happy to do this for any local members should they need it