Replacing heater hose.

i'm no expert, but this is what the enthusiast's shop manual says (grainger / shoemark, veloce publishing)...

1. A metal pipe runs back from the coolant inlet casting, the back end being secured on one of the exhaust manifold studs. This is the heater return pipe, the hose connection to which can be accessed at the back of the engine compartment. The other end of the hose connects to the heater outlet stub on the firewall (bulkhead). The heater hoses are easy to reach at the firewall end, and are secured by the usual clips.
2. The heater inlet hose is connected from the outlet cover on the back of the engine block to the heater inlet stub at the firewall. Access to the engine end of this hose will require removal of the ignition coil assembly. The outlet cover itself is retained by one 12mm nut, should removal be required. The cover also carries the water thermosensor. hope this helps... and i suspect your next question will be how to remove the ignition coil... ps. now is a good time to replace the rubber grommets on the firewall too.

That still sounds like a pain in the _ _ _!

Good luck Mal, Chris

The way to do it is to remove the coil pack first - not the easiest job.

If you haven't already done do, change the CAS O-ring first. This is usually what causes the hose to fail; oil dripping on it. The O-ring is another PITA to do; I did one yesterday morning. The problem is getting the dogs on the sensor to line up with the slots in the end of the camshaft. It can be hard to tell the difference between the resistance from a misaligned CAS and the resistance of a new O-ring, so keep trying and remember it might need a bit of a shove when it is lined up correctly. A little mirror is very useful so you can see which position the camshaft slots are in.

OK, getting there. Removing the coil pack took things from impossible to merely difficult. The factory spring clips holding the hose on are still fitted, was difficuly the get pliers in there. Might be easier once I get some worm screw type clamps instead.

Looking at the end of the hose, it certainly looks like the CAS seal is shot, I am off to research how to do this at Miata . net.

Thanks guys!

OK, all done! Been for a test drive, trying to determine if 6500 or 7000 is a better shift point :) Was a fairly straightforward job thank to the hints here & at Miata.net. The CAS seal was indeed shot, had the sealing characteristics of bakelite.