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Hi everyone,

Was underneath my mum's Mx5 doing an oil change on the weekend and I noticed coolant leaking out from no.4 and 3 intake runners, there was also just the beginnings of a weep from no.2. I haven't investigated too far as it is a daily dríven car and don't have gaskets and such on hand to reassemble.

Was hoping for some suggestions to what it may be.

To give some background the engine has previously blown a head gasket and was repaired 5 or 6 years ago (unsure what was done), since then it has had issues with with some corrosion in the metal piping in the cooling system, and has had a radiator replaced 3 years ago. it has had some issues with an erratic idle, cutting out on deceleration unless you work it down through the gears; i have been told this could be the ISC, but when Mazda did a timing belt and 100k service they said they couldn't find a problem, it stalled at the lights out the front of the dealer (so I don;t have great confidence in their findings).

Could this coolant leak be the ISC leaking into the manifold, or is it more likely coming from the head side? Or Is it some other part. I have never had this side of the engine apart before anddont have a reliable spare car for her atm so would prefer to pull apart with some spares on hand, rather then order and wait.

Any and all help and suggestions appreciated

Cheers,
Lachlan.

If not already seen, the following will give you a better idea of things on the cold side:
https://www.miata.net/garage/isc.html
https://www.miata.net/garage/CoolingSystemProblems.html
Other thing that occurs to me is did whoever fixed it last time clean up after the blown head gasket etc, in other words are the pics evidence of a new problem or the old problem.

Cheers for the response 93_Clubman,

I had already read through one of those pages, but not the other.
To answer your question this is definitely a new problem, when the head gasket blew years ago it was internal with all sorts of steam out the exhaust, but like I said before I stay out of that repair because it was just easier that way.

I have ordered a few gaskets and such and will pull things apart and diagnose the old fashioned way when they arrive, I'll also hopefully have my spare car working again by then that can be used which takes a little pressure off it need to be a quick fix.

Cheers again

Yeah, think you're going to need to take it apart to hopefully determine the exact cause.

cyreni wrote:...had issues with with some corrosion in the metal piping in the cooling system...
...had some issues with an erratic idle, cutting out on deceleration ... been told this could be the ISC...

That corrosion isn't uncommon on the NA6 these days & ISC issues on the NA6 are also common. IIRC, the most persistent idle/ISC problem was experienced by Gladiator on here who eventually found the issue.