So, I was parked, idling with A/C on taking a short nap before work, when I get a knock on my window - steam was coming out the hood, coolant dripping rapidly onto the ground and the temp gauge was at the top of the gauge (not over it, thank goodness).

Of course I shut it right off, and let it sit for a few minutes before turning it on to check if the fans were operating. They both were, and the temp rather quickly dropped down to normal. I don't know if they were spinning during the overheating, but I'd guess no.

Radiator fan relay maybe?



Doubt it's related, but yesterday I replaced the throttle body.

 

Did you make sure to disconnect the battery while installing your throttle body? Did you complete all of the relearn procedures? Intake air volume relearn, throttle position relean, accelerator position switch relearn, etc.? Reconnect all hoses and fittings securely without cracking? The reason why I ask is in extreme circumstances a big vacuum leak could cause overheating by creating an lean condition at idle when your not shooting fuel into it. Your internals may have taken a big hit during that event.

 

Yes, battery was disconnected (which let me know that it took me about 12 minutes from disconnect to reconnect).

All three relearns were completed, idle was ~700rpms after relearns.

The only hose that experience any flex was the one that attaches to the intake tube, and it appeared to be fine.

The strange part about it is that after the 5 minute break and restart, it was idling smoothly and at proper temperature.

I'm hoping the internals didn't take too much of a hit - the temp gauge was still under the top line, and the engine is acting completely normal now.

 

Alright well no matter what you can't have that happen again. I know that when I pass out in the G I dont want to be bothered. Was this the 6mt or the 5at you were in? Do you own an obd2 scanner that you can monitor sensors with? Did any CEL show around that time? If not scan it anyway, there might be a 1st trip saved in there. you can probably trouble shoot this by yourself. Just spend a lot of time watching and reading before you buy anything. You need to change your oil right away also and have a good look at what comes out. Once you have fresh oil warm it up and while its running pull the oil dipstick out. It may stutter just a bit but if it starts sounding like hot trash right when you pull it you may have bad compression.

Where did the replacement TB come from? Are you sure of the source? It seems there are slight differences between the different generations. The details are unclear to me but they have different part numbers. Have a look. http://www.infinitipartsdeal.com/par...tml?PNC=16298M

 

6MT

I had the ODB2 scanner right there handy since it was used to diagnose the throttle body the day prior. No CEL codes. The temp was down to about 217 F and dropping in the minute the car was running after re-starting it after a few cool-down minutes to check if the fans were both operating.

Replacement TB came from O'Reilly, it has the exact same Hitachi Model # on the electronics control portion, and I'm sure the aluminum body used to say Nissan Hitachi before they were required to machine off the Nissan part to avoid getting sued - a nice circular milling pattern is in place of where Nissan would be.

I'll give it an oil change this weekend, as I've got to prop up the front end to bleed out any air too.

Update, at idle, at reading 205 F. Been steady, idling for 20 min now with a/c on.

 

It's compelling to me that the whole thing nearly melted down and your ECU was just cool with it or something. Just after I read this I pulled over for a sec to read some data off mine. At idle with the a/c on and 90 degrees ambient temp my coolant sensor was settled at 190. I have only ever seen it climb to 207 under heavy load and throttle. Next time around check on what your absolute throttle position sensor is reading. Mine and a couple other cars I have seen hover around 1.2% to .8% throttle at a standstill in either park or N with a/c on.

It would also be a good idea to monitor your downstream o2 sensor voltages for any strangeness. If they fluctuate rapidly it's alright but if you notice them get stuck in a high or low range you've got something interesting. Lean is under .68v and rich is over.

Before I forget, there is a neat little trick that you can do to determine if you do infact have unmetered air getting into the engine. For this to work you must return your intake setup to as close to factory as you can, Disconnect your MAF sensor from the harness and start the car. You should hear the moment when the Ecu forces the engine into failsafe mode, it happens quickly. Let it continue to idle in failsafe and read what your short term fuel cut is on both banks is at, it should be -25, that is default. Neg means the computer is giving fuel If it is any higher than that, for example -15, you have a vac leak.

it could have been a coolant delivery issue too but unless it pretty much stopped circulating it would have taken forever to overheat like that. I watched a freinds G idle while dangerously low on coolant yesterday because he's an idiot and it took about 20-30 minutes to even start acting strange.

 

I am pretty sure that it wasn't quite to the melt down temp, but maybe our ECUs don't shut it down at danger temps.

Everything else is still exactly as it's been for years - minor coolant consumption (about a gallon every 6 months) and normal REVUP oil consumption. I might get a chance to do a rebuild in a few months to try and take care of those, but for now I suppose it was an isolated incident, but those are really the ones that remove your trust of the car.

 

Another update:

Sat in the car for a while watching the gauge. After about 15 minutes of stable temps, the gauge started rising. I checked under the hood and the passenger side fan wasn't going, temps slowly kept climbing. Turning the car off and waiting about 10 minutes didn't make a difference, as when I restarted it, the passenger side fan still wasn't going. A/C was on the whole time.

So, I guess it's just that motor's time. It outlasted the driver's side fan by about a year.

Update again:

Replaced the passenger side fan, so the issue should be fixed.

I'm not really sure why it takes so long before the heat starts to creep up. You'd think that it would start almost immediately, but instead it sits at normal operating temp for about 15min of idling before starting to creep up, even with the car fully heated up before idling. It's almost like the car switches to a different fuel mixture after idling for so long, which generates more heat, which the driver's side fan can't keep up with.