So here's the deal. I own a 2004 6MT Coupe. Yesterday, around 11:30PM, I was driving home on I-95 with my girlfriend sleeping in the passenger seat. Just cruising along in the left lane at about 70MPH, suddenly my 'SERVICE ENGINE SOON' light comes on and I immediately lose engine power and decelerate. When I hit the accelerator, the car would buck a little bit like it was going to accelerate normally, but then it would stop and continue to decelerate. I pull over onto the shoulder and I notice that my temp gauge is right at the bottom of the overheat area, so I shut the engine off and go open the hood. It takes me about 2 seconds to see the large amount of coolant that is all around the overflow tank; it must have spewed out of the vent on top of the tank. Curious enough, there was zero coolant left in the tank, however. It was totally empty.

I call my dad and he comes out with a gallon on mixed coolant and his code reader. Code was just an engine overheat code, nothing too serious. We let it cool down, fill the radiator and the overflow tank and I carefully continue down the highway at about 50MPH, with the heat and fans all the way up (although I never got any hot air out of the vents whatsoever). After about two miles the temp starts to go up past normal so I immediately pull over and shut the car off again. It has spat some coolant up into the overflow tank, but it didn't overflow and go outside the tank. Let it cool, fill it up, etc. We try again, and pretty much the same thing happens; this time, since the overflow was already pretty full, it spat a bunch more coolant out of the top of the tank. I call the tow truck and have it towed back to my house.

All of these symptoms point to a classic case of a faulty thermostat (or possibly a water pump). However, I just replaced the thermostat with a brand new one a few months (and a couple thousand miles) ago. I was also reading about electric fan failures on out G's, and I thought maybe that could be the issue as well. Any help is appreciated.

But on the bright side, I did see an R32 GTR drive by while I was waiting on the side of the highway.

 

Does your left (driver's side) fan work on the radiator fans? My right (pass) one worked but driver's side did not. This caused mine to over heat (low speed).

Maybe you just have air in your system?

 

I definitely don't think it was air in the system. Obviously I had air in the system the 2nd time it overheated but not the first. It's been months since we bled the cooling system and I've had no problems since then. When we bled it, we used a Lisle Spill-free funnel to bleed the cooling system meticulously; it took over an hour until we weren't getting any air bubbles out. My heat has been blowing hot since then, and usually cold heat is the first sign of air in the system. So based on all of this, I doubt that air in the system caused the problem.

I'm going to try and do some diagnosing of possible problems with the fans sometime soon (maybe tonight).

 

I'm going to guess you have an issue with the fans. It's common for one or both to fail and if they don't turn then yes, your motor will overheat. Turn the car on and with the AC engaged and going full blast both of your fans should be on. If they're not that's one problem identified. Also make sure your water pump didn't fail, if it isn't circulating coolant that could also cause the motor to overheat.

 

I followed the ByTheBay video on Youtube on changing coolant (thanks for advice on changing fans btw, very simple!) and took it out for a drive today. After it "overheated" a touch this morning, now it blows hot air. Hasn't overheated since.

Otherwise... the fans did not turn on with 90* set on the temp gauge, full blast air, and ac on??? Weird. Brand new TYC fans. Oh Nissan .

 

As others have mentioned turn on AC to see if both fans are running.
If not, replace them.
On a 2004 vehicle which is close to being a fifteen year old vehicle,, replace the water pump, thermostat, radiator, cap, coolant, hoses, and belts.
Use only OEM parts.
If you purchased some cheap-a$$ thermostat made in China that could be a problem also?
Most original parts on a fifteen year old vehicle are at or near end of life

Just my $.02

Telcoman

 

I assume when you say "AC on full blast" you mean set the interior temp to the minimum, fan speed on 5 and AC on?

I've been looking at the wiring diagram for the fans & accompanying relays. I'm going to get out there with my multimeter and a 12V power supply later today and test the fuses, relays, and fans to make sure they are good.

My next step after that would be to take the thermostat out and boil it to see if it's working properly as well. I guess it's possible that a brand new thermostat failed in a few months, but it seems unlikely. Regardless, it's worth taking a closer look at.

And if both the fans and the thermostat are working as they should, I guess that leaves only the water pump as the culprit. Which really, really, really, really would suck. For those of you that don't know, our VQ35's have a timing chain-driven water pump, and it is a MASSIVE PITA to change. I'm pretty mechanically savvy and have all the tools to do the job, but I'm still not sure it would be something I'm comfortable with. Mess up one thing and you can cause serious damage to your engine.

 

I would unplug the fan harness and provide 12V straight to the fans. That's how I tested my fans and they would spin real slow or not all. I bought a replacement for less than 100 bucks and swapped it out in about an hour.

I also had a failed water pump about three years ago it was the bearings that went out. I attempted to change it myself and the engine turned over slightly (when doing loosening the tension), there is a crank locking tool that I didn't use. So, I experienced your fear of tackling this job, I went ahead and did a primary timing chain on my engine. It was a real PITA, but my car is fine and didn't suffer any damage.

 

Yep that's my plan. Let's hope it's just the fans...

How did you know it was your water pump that went bad? So after you accidentally turned the engine over a little bit while doing the water pump, you had to then replace the whole timing chain? That's pretty much my nightmare scenario...

 

I added 0.5 cup of Coolant after the road portion of the breeding procedure. Heat is hot and it doesn't overheat anymore. Maybe you just need more time OP. I replaced the TYC fans, I repeat.

 

I knew it was the water pump, since it made loud screeching noises. I took off the belts and it was still there, so i knew it was the pump.

I didn't "have" to buy a new chain. But, since i had the whole front apart to set the timing, i decided to replace the chain, tensioners, and guides. I've heard chains can stretch, so i figured why not and i had about 100k at the time. My car has about 160k now on the clock.

I'd look at your thermostat first though. Your fans should spin while at highyway speeds and provide cooling.

 

Just thru simple logic I'm calling it the thermostat.

first of all, you are only building pressure on the top half of the cooling system (hence spewing from the overflow); this suggests a blockage, not a lack of flow. Second, thermostats are very simple devices that work simply, but can just as simply fail. Not uncommon at all to buy one that simply doesn't work straight out of the box.

also, you have air in your system now regardless of what is wrong, so it'll need to be bled.

if I were you I would break off the valve of your current thermostat, reinstall it and run water from the top rad hose (into the motor) and make sure it's draining from the bottom of the water jacket, then from the top of the radiator making sure it's draining at the bottom of the radiator. If it's draining (aka no internal blockage) replace with a new thermostat and bleed the system.

it would also be wise to rent a cooling system pressure tester to make sure you aren't pulling in air from a hose somewhere or the radiator itself. They're pretty self explanatory.

 

After I bled all the air from my system I no longer have any issues.

 

+1

Start at the thermostat because it is an easy diagnose/fix. Depending on the type you bought, it could fail earlier. They sell the type that if it fails, in it will stay in the open position, which is what I put in my old Mazda when the t-stat failed.

Then drain/bleed and replace the coolant on the whole system and go from there.

Hopefully your fans do work. At least those are easy fixes also.

 

Hoping it was your thermostat. I was having same issues on my 03 sedan....started with most logical...thermostat and system bleed. No issues with waterpump. Still continued to overheat. After deep dive, turned out to be headgasket. With some of the other issues, result is the need for engine replacement. Pretty disappointing with only 123K miles.