Froze My Miata Engine - How Screwed?

Well, I've been leaving my Miata outside to make room for my SC300 build. It's supposed to get real cold tomorrow and I remembered that I'd left straight water in the cooling system from the last track day. When I pulled the radiator cap off (before starting the car), coolant started leaking out of the back of the head. Apparently, it had gotten just cold enough to freeze one of the nights when the car was outside and something cracked. Upon closer inspection, it appears that there's a crack in the CLT sensor housing.
I can just barely see back there, and it looks like there's a crack in that casting and water sprays out near that. So, I'm looking for a replacement: http://grassrootsmotorsports.com/forum/200x-classifieds/wtb-miata-16-clt-sensor-housing/76928/page1/

I'm wondering if anyone else has had the same piece crack before, or has any other frozen miata engine stories. I'm really hoping this isn't the end of the engine, though it is just a 1.6L...

I needed to move the car so I started it and ran it for a few minutes with water leaking out around that housing. Oil pressure was good, temp started coming up like normal (before I shut it off). I didn't notice any coolant/oil mixing in the radiator or sump, so that was good, but I only ran it for a few minutes, so that might not be conclusive.

I've only got 1st hand experience with freezing one other engine (an '89 integra) and it cracked the head and was immediately mixing oil/coolant.

Obviously I won't know for sure until taking a close look at the back of the head, but what do you guys think? Did I dodge a bullet here?

Impossible to predict, fix whats apparent(JB weld?) and find out. I'd roll it over by hand before starting it again, in the event you cracked a cylinder and it fills with water.

My mom didn't get her 4.3L boat motor drained in time one year. It was pooched.

friend of mine had water in the 350 of his impala. I undid the belts and started it up to melt the internal ice.. one of the "freeze" plugs got pushed out, that was the only damage

Replace the known problem, then do a pressure test.

Might as well do a re-route if you have to replace that berkeleying part anyways.

greetings! just got a '92 SM and am sorting it out and encountered the exact same thing (cracked rear coolant sensor housing). apparently the former owner stored it with only water this past winter. wondered in your case if it was just that housing or was the motor toast as well? thanks in advance!

In reply to Keith Tanner: That's right! never JB weld, ad just fix the known problem, temp fixes and the like are exactly that temp, or may end up cuasing more problems down the road.

changing coolant when it get's cold is alot cheaper than wondering how the 10% expansion from water is going to effect something, it may not be such a cheap fix next time.

Loving these lil roadsters wrote: changing coolant when it get's cold is alot cheaper than wondering how the 10% expansion from water is going to effect something, it may not be such a cheap fix next time.

girlwerk wrote: greetings! just got a '92 SM and am sorting it out and encountered the exact same thing (cracked rear coolant sensor housing). apparently the former owner stored it with only water this past winter. wondered in your case if it was just that housing or was the motor toast as well? thanks in advance!

Yeah, it turned out to be just the coolant sensor housing. Wasn't too bad to get at either - just needed to take off the coil packs and heater hose to get back there.

I would say that I caught this pretty quickly - the car was outside for one or two nights with temperatures right around 30F. If it were stored all winter in really cold temps, I could see much more serious damage occurring.

thanks! just ordered the new housing and draining the oil now to take a look. fingers crossed my story turns out like yours. thanks again!

In reply to girlwerk:

Yeah, good luck!