Yesterday I got caught in really high traffic, around 3 to 4 hours just stuck in stop & go type of traffic. The car always ran normal but eventually I noticed the temp gauge rose to the very top. After this I only drove the car for about 10-15 minutes just to a place I could stop the car and turn the engine off. I turned the engine off and waited around 1 hour and the temp gauge dropped below the middle, so it was safe to drive home. While driving home I didn't catch as much traffic and managed to keep the gauge below middle.

Today I went to check the coolant level and it was below minimum. Didn't look contaminated with oil, but the level was very low. I'm going to replace it when I get home.
I do not know if the coolant level was already this low before yesterday, or if it just evaporated from overheating (the car had a check up about 3 months ago).

What steps can I take to diagnose if there was any damage while overheating yesterday? Scanned for error codes, none found. Car starts and runs fine so far. Can't hear any knocking or misfire whatsoever.
Also, does anyone know at which temperature the gauge hits the top?

 

Check for coolant leaks after you refill. If it got that low, air was likely introduced into the system so you'll need to "burp" it to get all the air out.

Or, if you think it was leaking, now would be a good time to conduct a pressure test of the cooling system to see if you can identify any leaks.

If the temp gauge pegged, then obviously that's not good. Check the oil dipstick or change the oil to see if it's milky/watery signifying a head gasket failure.

It probably overheated based on the low coolant level, but also verify the radiator fans are working correctly. Even if they spin, they may not spinning fast enough to draw enough air into the radiator.

 

Probably going to be fans.

 

What Dark & Heel said, my guess is fans. Note: Both fans should turn on when you activate the AC (Max cold).

Heel makes a good suggestions as well. Burp the coolant system. If you're running silicone radiator hoses, go back to OEM. Silicone hoses are great for track/race cars, but not for daily drivers. They sweat the water out (evaporates) and unless you regularly check and top off your coolant level, you can run into an overheat scenario.

If the temperature is generally stable when moving at speed and this only happened when in prolonged stop and go traffic, then the electric radiator fans are most likely your issue. There's always a small chance that your thermostat is sticking, but unlikely under the conditions you described. After getting the engine that hot, it's a good idea to monitor your coolant system and engine oil closely. If you still have the OEM radiator with the plastic end-caps, check it for leaks/seepage or cracks forming (hard to do on a 350Z). Check your oil level regularly for a while, make sure you don't have chocolate milkshake. If you see/hear bubbling at the overflow tank, odds are you have a blown head gasket. You can also get head gasket test kits that stick on your radiator and react to combustion gases through the cooling system. One of these kits will give you a definitive answer to the head gasket question quickly.

Good Luck!
-Icer

 

Thanks for the suggestions. I did a complete coolant replacement, and the old fluid came out very clean, pretty much like the new one.

The fans do come on when I turn on the AC, however they did not come on automatically when the engine came hot. Is this an issue with the fans or something else?

 

Bad advise, but just keep the A/C on. I did this for years when chasing a low idle problem after I turbo'ed my car.

 

The ECM controls the cooling fan relays (I think there are three) which are located in the IPDM E/R.

I have attached the FSM portion for DTC P1217 which deals with overheating. Hopefully, it gives you some guidance.

 

You could have a bad ECT (Engine Coolant Temp Sensor), or possibly a bad harness connector (continuity issues). If you have a scan tool that can look at live data, I would watch the engine temperature. I can't remember, but there might be more than one coolant temp sensor. One for automatic fan control and another that sends data to the gauge cluster or climate control system.

Look over the FSM pages that Heel shared, I think it's all in there.
Cheers!
-Icer

 

Update:
Today I got caught in very bad traffic again, it was raining heavily. The car held up better now after replacing coolant, keeping the temp gauge always at 2/5ths for about an hour of stop & go traffic always in 1st gear, but then it started going up and reached the redline again in a matter of 30-45 something minutes.
But luckily, 5-10 minutes after that the traffic cleared and I was able to speed up, and the moment I did it the temp gauge dropped very fast, it only took 10 minutes to go back to normal operating temperature.

Could it just be that this car wasn’t built for this kind of traffic? It does look like it has very poor airflow for an engine of this size.
I’m a new owner by the way, I have it for only about 2 and a half months, bought it with 111k miles on it.

You reckon getting a race radiator and fan setup could help with this?

I do have a bluetooth scanner, could have it display live data in my tablet screen, I’ll be sure to try that out. At what kind of temps should I absolutely turn the car off?

 

Lol no. All cars should be able to withstand stop and go traffic no matter how bad it is.

How's the coolant level now? Is it the same or lower?

Really sounds like a fans issue. If the fans didn't kick on when you got to the correct temperature when it was sitting idle previously (post #5), why did you risk driving it?

You're about to have bigger problems than a faulty sensor or bad fan motor(s).

 

The OEM/stock electric fan assembly is better than most aftermarket options. Keep them. A racing radiator helps, but you will still overheat if your electric fans are not engaging when they should be.

You need to monitor the Engine Coolant Temperature Sensor. The Electric Fans should kick on (low speed) at 208*F, once you hit 212*F they should switch to high speed, this is true if you're simply idling (not moving).

Based on the FSM procedure Heel shared, there's only one Temp Sensor (I was wrong earlier) and it's located on the rear coolant hardpipe (passenger side) that connects to the back of both cylinder heads. Based on the fact that you're still getting a good reading on your gauge cluster, then I would say you have problem with one of the Fan Relays or the signal from the ECU is not reaching the IPDM to turn on the fans based on temperature data. You have already confirmed the Fans kick on when you engage the AC, so that rules out a fuse issue or locked up fan motors.

Get to the IPDM (inside battery compartment under the hood). And try swapping around the Fan Relays. There should be 3 total.
If the fans are still not working as designed, and the relays test good. Then there's a signal issue from the ECU to the IPDM. For that you would need experience troubleshooting wiring faults or have a bi-directional scan tool to do tests with. Worst case scenario you have a bad computer module.
Good Luck!
-Icer

 

It drives fine and doesn’t overheat on regular drives, just when I get caught in rush hour traffic for over an hour.
The coolant level dropped, but when I replaced the coolant I was only able to put in +/- 6 1/2 quarts before it overflowed. I followed manual instructions to burp it but maybe some air is still inside? I did not drain the engine block, just radiator though.

I ordered a gasket test kit and it will arrive this weekend so I’ll test if I’m leaking fumes into the cooling system. Though the coolant looks clean, the oil does not look muddy either.

I will have to check this out. I did pull the fuses and they looked fine to me, but didn’t test the relays. Battery is getting old though, might also replace it.

Now that you mentioned it, I do hear a faint fan noise when idling. So they must be working at a low speed all the time and they just never kick in to higher speeds when the engine is heating up, only when I turn on the AC to max.

As for the fan upgrade, I was thinking of buying this setup:
https://fmic.eu/324889-mishimoto-mmf...s-350z-03.html

I thought maybe the shroud could seal better, as it has a sealing strip that seals the shroud to the radiator, and it would pull only fresh air from the outside. This of course would be paired with a racing radiator.
Am I still better served with the OEM ones, provided they aren’t malfunctioning?

 

Again, assuming the factory Fan Package is in good working order, I would stick with them. They are very high quality and offer excellent airflow. If you really want to upgrade your radiator, the Mishimoto or Koyorad options are good (Although I trust Koyorad more myself). Don't get sucked into the marketing of aftermarket parts. A lot of R&D goes into OEM components and sometimes there's a good reason for factory parts to be so expensive (usually when it comes to sensors and electronics). I think the only reason or advantage to swapping out the OEM fans is if you have clearance problems. The aftermarket fans are usually lower profile, which will give you some added clearance between the fans and front of the engine. I'm personally running the Koyorad 48mm radiator with the OEM fan package. It works amazingly well, installation wasn't too bad either, but I did have to make some relief cuts into the core support to provide clearance for the AC condenser mounting brackets.

Before running out and ordering up some juicy new parts though, you really need to get this overheat issue sorted. The symptoms described are all classic signs of the fans not turning on when they should be. I think you might be lucky and only have a failing relay. That "faint fan noise" you hear while idling could be the clutch assembly (assuming you have a 6MT). Or it could be one of the idler pulley/tensioners, PS Pump, Alternator, or AC Compressor clutch/pulley. The electric fans are loud and noticeable when they kick on. The engine RPM will adjust from the electrical load whenever they switch on and off.

If the battery is getting old, might as well replace it. You have to remove the battery to access the IPDM relays.

Good Luck!
-Icer

 

OEM fans are more effective and quieter than Mishimoto, don't get those.