Engine just about died...long read, please hang in there.

[LSDrift]

So, let me start from the beginning. I've recently put about 3500 miles on my new S2 RB25 swap in my S13 over the past month or so. It's been running like a dream and everything I wanted it to be, with only a minor issue of running hot on the highway if the ambient temperature is 80+ F. I was running dual 12" FAL pullers and an S14 DE radiator. I've flushed the coolant 3 times and used Prestone radiator cleaner twice now. Most recently I did it last Thursday and have been running 100% distilled water the whole time. When I flushed the coolant Thursday I noticed that it only took about a gallon of water before it was full. I drove to work Friday morning and then added more water that afternoon when I left work for another town about 3 hours away. I noticed on Saturday that the coolant had been pushed out of the burp tank a little but was very white in the stains it left inside the engine bay. Didn't think much of it due to the cleaner in it, and it wasn't the first time it pushed a little out of the burp tank. Now Sunday, I came out to the car to head back to where I'm from and noticed a big dried up white puddle. Thought it was odd but didn't think much of it again and added more water to the radiator to be safe. Got headed out of town and noticed the temperature was fluctuating somewhat erratically. Kicked on the heater and noticed no heat coming out to speak of. This is where I went wrong.

Kept driving for another mile or two and all of a sudden noticed an extreme lack in power and throttle response.
Went to pull over to check things out and the engine shut down. FML. Opened the hood and instantly saw a relatively small amount of smoke and smelled burning. The radiator was hissing and I was freaking out. I left the car off and let the fans run for as long as they wanted for about a half hour. Odd thing was that the fans shut off after only about 5 minutes of running. So then I tried to restart the engine. It did after cranking about 5 times rather hard and then idled ok but now with a ticking noise. So, obviously, I shut it off right away again. Waited about 15 minutes and then tried again because I was about a quarter mile away from a gas station. It was very hard to start at that point but finally did and ran enough to drive.

So I began driving back to the station and about 50ft down the road the ticking just stopped.
In talking with a few folks it was clear that I had to have a problem with the thermostat, which I should've realized when the heater didn't put any heat out. So, right away I tore into the bay and ripped out the thermostat which was only open a very small amount even being extremely hot. I then put it all back together, no thermostat, and refilled the radiator etc and started it back up. Instead of a 3 crank start like normal, it was more of a 5 crank start but then idled like nothing ever happened. So I shut it off and went to look things over again. Found a small hole in the radiator that was leaking relatively fast.

So, bottom line is, why would it tick after overheating and then stop? Bubble in a lifter from too much heat? My first thought was a bearing but I am thoroughly confused now.

If you read this whole thing then God bless you haha. All opinions are welcome, especially if you've seen a similar situation before!

Thanks a ton!

[kouki-gymkhana]

I had a similar experience about 4 years ago with my swap. I lost all the coolant while driving at highway speed when a heater hose burst. The car was driving fine and then I noticed that the temp gauge was FALLING and when I finally realized what was going on, the car went into limp mode and then shut itself off. I was eventually able to start it after it cooled down and I limped it home about 1/2 mile. The result? A blown head gasket and a slightly warped head.

The ticking noise you described might have been knock/detonation because the engine was so hot. If so, it would resolve once the temps cooled down. I would be worried that you might have a blown head gasket if I were you.

[LSDrift]

Yeah I was worried about the head/gasket too. I've got ARP head studs and a fresh head gasket so I've at least got that on my side. I didn't even think about knock being that sound ha thanks.

If the head gasket were blown though generally I would be seeing white smoke in the exhaust right? I think there are some instances where it can be blown but not have the white smoke production but I'm not sure how to tell if that's the case. I'll be dropping my oil this weekend and looking for metal shavings and coolant in it.

Was your head warped enough to warrant a new one?